ASM Distinguished & Waksman Foundation Lecturer Roster
The American Society for Microbiology Distinguished Lecturer (ASMDL) program consists of a scientifically-diverse roster of 16-20 lecturers who are available to present at ASM Branch meetings throughout the U.S. Included on the roster are two Waksman Foundation Lecturers, supported by funding from the Waksman Foundation for Microbiology, and selected for their expertise in antibiotics, translational research and/or environmental microbiology. Browse each lecturer's personal statement and lecture descriptions:
As a student, post-doc and junior faculty member in Rochester, it was a privilege to have two seasoned and dedicated mentors who selflessly committed their time, experience and knowledge to support and guide my career development. By the mid-90s, I had five Ph.D. students and one postdoc under my supervision. I was the PI/PD of a T35 for minority professional students and wrote my first T32 in the late 90s. For the past ten years, I have been the PI/PD of the largest T training program at the University of Florida, which funds three dual-degree (D.M.D.-Ph.D.), three Ph.D. and five postdoctoral fellows. My research program has been continually funded from NIH for the past 28 years, and I am presently PI on three R01s and co-PI on one R01. Since 2000, 18 postdocs have trained in the lab, with five still in training. Of the 13 who completed training, all remain in science and 11 are in faculty positions. I believe the ASMDL program will allow me to benefit students, postdocs and junior faculty at regional ASM meetings by sharing the knowledge and experience gained from a decades-long commitment to research and mentoring, while “giving back” to an organization in which I have held membership since the mid-80s. The inlusion of expertise in oral microbiology and the oral microbiome (ideal for studying bacterial behaviors and interactions) in the ASMDL enhances the breadth and scope of the program, while offering meeting attendees novel perspectives on concepts that are broadly applicable to environmental, pathogenic and applied microbiology.
Lecture Topics and Descriptions
Probiotic Mechanisms of Beneficial Oral Bacteria
Dental caries and periodontal diseases affect a large majority of humans and are driven by environmental inputs that effect compositional and behavioral changes in the oral microbiome. Overwhelmingly, research has focused on known or putative pathogens, with little effort devoted to understanding how organisms that are associated with health moderate the pathogenic potential of oral biofilms. Using combinations of high-throughput screening, phenotypic analyses, whole-genome sequencing, and functional genomics, we are characterizing a collection of organisms to understand the molecular basis for how these bacteria may promote health and antagonize the establishment and persistence of oral pathogens. The work provides the foundation for the rational design of probiotic strategies to promote oral and systemic health.
Complexities of Intercellular Communication in Regulation of Genetic Competence and Stress Tolerance in Streptococcus mutans
Two quorum-sensing (QS) peptides of Streptococcus mutans regulate bacteriocin production, development of genetic competence, biofilm formation, programmed cell death and tolerance to a variety of stressors (e.g., acid, oxidative). Using microfluids and various in vitro models, we have studied the physiologic and molecular basis for differential responses to the QS signals, including stochasticity in sub-population responses and hyper- or hypo-responsiveness depending on a spectrum of environmental conditions. Unlike any other organism examined, there are at least three peptides encoded within known genes of S. mutans that are differentially expressed and act as primary regulatory effectors, along with small nucleotide alarmones, to create a complex decision network that integrates physiologic status of the cells with the commitment to activate regulons required for DNA uptake, stress tolerance and virulence.
Regulation of Carbohydrate Metabolism: Long-term Memory and Cheating Behaviors in Oral Streptococci
Oral streptococci rely almost entirely on their capacity to catabolize a wide range of carbohydrates to generate energy for growth. Because of the host diet and diurnal rhythms, oral microorganisms lead a feast-or-famine lifestyle and have thus evolved highly complex regulatory pathways to optimize the use of preferred and non-preferred carbohydrates. In certain pathogenic isolates, bet-hedging and cheating behaviors, in which sub-populations of cells can acquire long-term memory induced by certain preferred carbohydrates that precludes the population from utilizing non-preferred sources, are now evident. Further, the expulsion of hexoses during catabolism of disaccharides allows populations to develop cheaters that bet-hedge and repress catabolic systems while utilizing hexoses released by a sub-population. This behavior likely evolved to optimize persistence and ecological dominance as humans transitioned from a hunter-gatherer lifestyle to a diet rich in many different carbohydrates.
During my career, I have developed expertise in various parasitic protists that affect human health and I intend to bolster and expound the fields of intracellular parasitism and parasite-mammalian cell interactions through my lectures for the ASMDL program. Since my recruitment to Johns Hopkins University in 2003, I have been committed to mentoring scientists of many different experience levels, including Faculty Research Associates, postdoctoral fellows, Ph.D. and Master of Science students, as well as international visiting scholars and undergraduate students, including underrepresented minorities. I have weekly meetings with individual students and fellows during which we rigorously analyze new findings, debate possible interpretations and generate future ideas for their projects. Through these meetings, the students and fellows learn my high expectations regarding scientific rigor and responsibility. During my career, I have also been committed to ASM by publishing and reviewing manuscripts and performing editorial activities for ASM journals, and presenting as an invited speaker at ASM conferences, which has led to the honorific AAM (American Academy of Microbiology) election. One of my strengths resides in my eclectic interest in various microbes besides parasites, and their strategies for exploiting their respective hosts. To this point, my lab performed original comparative studies of co-infection of mammalian cells with Toxoplasma and Chlamydia sp., highlighting their similar modus operandi in colonizing mammalian cells, as an example of convergent evolution. Finally, I believe that it is critically important to study parasitic protozoa not only because these organisms are major human pathogens but also because their remarkable biology constantly challenges dogma thought to be universal in eukaryotic biology.
Lecture Topics and Descriptions
From Cell Biology to Therapeutics: Apicomplexan Parasites Revealed
This lecture exposes the strategies by which Apicomplexa, obligate intracellular parasites (e.g., Plasmodium, Toxoplasma, Cryptosporidium), adapt and exploit their mammalian host cells, leading to disease pathology. The stratagems developed by these crafty parasites extend from the interception of host cell vesicular trafficking and salvage of lipids to the remodeling of the parasitophorous vacuole to support parasite differentiation and replication.
Catching What You Eat: The Secret of the Intracellular Tenure of Toxoplasma gondii
This lecture focuses on the cell biological aspects of the mammalian cell–Toxoplasma interface. Upon infection with Toxoplasma, the mammalian cell acquires a novel dynamic compartment – the parasitophorous vacuole. The cellular and molecular mechanisms underlying the targeting of mammalian trafficking pathways and the recruitment of host organelles to the parasitophorous vacuole by Toxoplasma for lipid acquisition will be described.
Autophagy as a Potential Therapeutic Target and Vaccine Development Against Malaria
This lecture emphasizes the molecular and cellular mechanisms developed by malaria parasites (sporozoites), newly-invaded into the mammalian liver, to be differentiated into replication-competent forms (trophozoites) in hepatocytes. This metamorphosis involves organelle clearance in converting sporozoites through a process of parasite-induced autophagy. A Plasmodium strain overexpressing the autophagy gene ATG8 is a promising pre-erythrocytic vaccine candidate.
As an undergraduate student, I was a Microbiology major focused on a research career in immunology and medical microbiology; however, a chance meeting with a food microbiologist followed by a summer internship at the Kraft-General Foods Department of Biotechnology opened my eyes to the fascinating possibilities in the food microbiology discipline. After nearly 30 years, three degrees, and achieving tenure at a major university, I have not forgotten how a chance meeting can radically change a student’s life. Through my undergraduate teaching responsibilities (a freshman seminar, and junior level required food microbiology courses) and graduate courses (microbial physiology of foodborne microorganisms, and introduction to food microbiology for food scientists), I have tried to bring to students the excitement I felt after realizing my true passion. More recently, I have used this energy to establish an undergraduate summer research program at Penn State, funded by the USDA. This program supported 16 students in 2018, and 13 in 2019, with the goal of introducing students from undergraduate-centric colleges and universities to food microbiology research. Notably, this program involves the University of Puerto Rico Aguadilla, and in Fall 2019 a student from that institution joined my lab to begin her Ph.D. As an ASMDL, I would like to communicate with students why microbiology is such a fascinating discipline, and to open their eyes to the wide number of career opportunities, including those in the agricultural, engineering, and environmental disciplines.
Lecture Topics and Descriptions
Virulence Depends on the Company You Keep
As humans, our attitude and well-being can be impacted by those around us. Bacterial pathogens are not so different. One focus of Dr. Dudley’s lab is whether the course of infection by the foodborne pathogen E. coli O157:H7 varies in response to specific strains of commensal E. coli colonizing the intestines. This research-focused talk reveals ways that the production of toxin by E. coli O157:H7 changes in response to its neighbors, and highlights research from other groups that demonstrates how the gut microbiota directly affects other essential traits including adherence. This talk provides a model for how disease susceptibility could be due, in part, to individual differences in the gut microbiota.
Whole Genome Sequencing: A Leap Forward for Food Safety Regulators, a Massive Concern to the Food Industry
The rise of genomic technologies has transformed how we investigate foodborne outbreaks. Dr. Dudley’s lab leads the Pennsylvania consortium of a Food and Drug Administration effort called GenomeTrakr. The goals of this program include bringing whole genome sequencing to state public health laboratories for the purpose of defining routes of foodborne pathogen transmission in unprecedented detail. This talk will describe how foodborne outbreaks are investigated, the promises delivered by this new technology, and stories of foodborne outbreaks that may not have been solved before the genomics era. This talk will also describe unintended side effects of this powerful tool, specifically the apprehension it is creating among U.S. food producers.
Make Mine Raw, Unprocessed, and Preservative-free Please
The field of microbial ecology teaches us that perturbing a system can alter community composition. These rules certainly apply to food safety. Several foodborne pathogens of great concern today were unknown 40 years ago, and our news seems filled with stories of widespread illnesses resulting from contaminated foods. These changes are partially the result of our improved detection and tracking methods. However, we should not discount the role played by consumer demands for “healthier” foods, less food processing, and preservative-free foods. This talk is tailored to a broader audience and suggests how changes in food culture and attitudes over the past century have impacted pathogen trends. It also argues that those who demand raw, unprocessed, and preservative-free foods should educate themselves about why these “undesirable” methods were implemented in the first place by the food industry.
Don’t Know What You Want to Do with Your Life? Join the Club
Dr. Dudley has given this talk to numerous groups including the student chapter of the International Association for Food Protection at their national meeting. The purpose is to dispel the myths that most established science professionals knew what direction their careers were headed when they were students, and that career paths typically follow a linear trajectory. It also includes his opinions of the top 10 things students should appreciate as they transition to the working world.
The ASMDL program offers a unique opportunity to meet and share with audiences around the country. As a yeast geneticist, I occupy a bridge between classic microbiology and eukaryotic cell biology, using fission yeast as a model system to study fundamental questions relevant to cancer and development, and I look forward to an opportunity to highlight eukaryotic microbiology! I bring to the program my own research, and my advocacy for the use of model organisms in biology. Importantly, I have a long-standing commitment to the career development of junior scientists, as seen in my awards as a mentor and my leadership in both graduate and undergraduate training and education. I have also worked for diversity and inclusiveness in science, and have been recognized for my work particularly in advocating for women (including the Roche Diagnostics Alice C Evans Award from ASM in 2011). I am also active in public policy issues as a current member of the public affairs advisory committee of the ASBMB and as the ASBMB representative to FASEB’s policy committee, and I am enthusiastic about encouraging the involvement of young scientists in policy and science advocacy. I have been a member of ASM for many years, and was elected to the Academy in 2014. I am eager to share my experience and viewpoints broadly with the ASM community.
Lecture Topics and Descriptions
How DNA Replication Stress Is Linked to Genome Instability
The proper response to replication stress is considered to be the first barrier to malignant transformation. Using a fission yeast model, we are investigating the mechanism by which the cell responds to global and local stresses. Yeast don’t get cancer but we can study cancer in yeast.
Differentiation and Development in a Model System
On the order of 25% of human conceptions end in miscarriage, largely due to early meiotic defects including aberrant chromosome segregation. Fission yeast undergoes a streamlined meiosis allowing us to investigate the processes that ensure normal chromosome segregation and viable gametes.
Dissecting Fundamental Cell Biology with Yeast Genetics: A Primer
In an era of high-throughput sequencing, we still use classical and molecular genetics to dissect biological function. How, exactly, do we do that? From isolation of mutations to suppressor screens, the art and design of working in yeast and knowing what they look like.
I am a physician scientist appointed in microbiology and medicine. I write papers, hold grants with experimental physicists, and have developed a passion for cross-disciplinary teaching. As a residency director, I founded a journal club that brought M.D.-Ph.D. students and residents together to discuss basic science papers that have impact on clinical outcomes. As a division chief, I have integrated my Ph.D. students and postdoctoral fellows into ID grand rounds and ID journal club, where they learn about clinical challenges and teach progress in basic science. Together with the head of microbiology, I teach a translational pillar for medical students on basic science of urinary tract infections. I have developed and taught a 3-week intensive summer course on emerging infections for undergraduate students at the University of Freiburg. That course also included skype interviews with economists and lawyers working in Global Health. I have been an ASM member since 1999 and consistently attend ASM meetings. I helped organize the ASM sponsored 8th International Conference on Cryptococcosis in Amsterdam. I publish in ASM journals and serve as reviewer. I am an active member in the ASM community and serve as councilor of the Medical Mycology Society of the Americas. I chair its award committee that selects the best graduate student abstract. I also serve in multiple roles at the annual IDSA meetings and on its awards and research committees. In addition, I serve as the President of the New York ID Society.
Lecture Topics and Descriptions
COVID-19: The Pandemic that Caught Us Off Guard
An intimate report on the COVID-19 pandemic from a physician scientist and ID Division Chief who worked on the “front lines” combating the disease.
Replicative Aging in Pathogenic Fungi Results in Enhanced Resilience in the Host
A novel concept of how the aging of a pathogen leads to heterogeneity in a fungal population in the host. The speaker discusses why older fungal cells exhibit higher resistance to phagocytic uptake and killing as well as why aging leads to antifungal resistance.
Infections with Multidrug Resistant Enterobacteriaceae in the U.S.
The speaker will discuss the importance and epidemiology of multidrug resistant enterobacteriaceae in the clinical setting. She will also discuss challenges that need to be overcome to develop novel treatments.
Developing Monoclonal Antibodies for Treatment of Human Infections
The speaker will discuss the basic process and challenges of developing monoclonal antibodies to treat human disease.
The Development of Antibody-based Therapies for Resistant Bacterial Infections
The speaker will discuss the challenges of developing antibodies against bacteria, including drug resistant bacteria.
It is an honor to be selected for the American Society for Microbiology Distinguished Lecturer Program. I take pride in delivering entertaining and educational seminars targeted for broad audiences where I minimize jargon, carefully explain experiments and encourage questions along the way. I recall participating in a Branch meeting held at Mankato State University several years ago, when I had the privilege and honor of picking up Stan Maloy at MSP airport, and then driving him (and a van full of students from both my lab and Daniel Bond’s lab) to Mankato, MN, where Stan would be presenting as a participant in the ASMDL program. I first got to know Stan at a Midwest Microbial Physiology meeting when I was a graduate student. The drive to Mankato chatting with Stan reminded me of how important it is for senior faculty to interact with students and postdocs (and junior faculty!!). There are many pathways to success (and happiness) and the more young scientists can learn about these pathways from established scientists, the better equipped they will be to find their own way. Sharing experiences from my scientific journey, and the journeys of my students, with students and postdocs at ASM Branch meetings is something that I would be excited to do. While I cannot match Stan Maloy’s ability to engage, entertain and educate (very few can), I can promise to bring his level of enthusiasm for microbiology!
Lecture Topics and Descriptions
Electromicrobiology: How Bacteria Make Electricity and How Bacteria Eat Electricity
The microbial world is truly a wondrous place where metabolic innovation has driven an incredible amount of diversity. Where energy in chemical reactions can be captured, life finds a way. Dissimilatory metal reducing bacteria grow by using metals like iron or manganese as an electron acceptor for respiration. Neutrophilic iron oxidizing bacteria run a similar reaction, but in reverse. We can replace the iron used by these bacteria in the lab using poised electrodes. In this lecture topic, I will discuss the best understood model microbe used to generate electricity (Shewanella oneidensis) and discuss recent advances on our studies of a model microbe that consumes electricity (Mariprofundus ferroxidans).
How to Train Electric Bacteria
Some bacteria have the ability to interface with electrodes that can act either as an electron sink or as an electron donor for metabolism. However, our ability to rapidly understand and engineer them is hampered by our lack of genetic tools. Here I will describe implementation of oligonucleotide-based genetic engineering and CRISPR/Cas9 counter-selection to rapidly alter gene sequences in the electricity producing bacterium Shewanella oneidensis. Unlike S. oneidensis, which is metabolically versatile, some bacteria in the environment know only how to live one way. Mariprofundus ferroxidans is an obligate chemolithoautotroph, using energy conserved by the formation of rust to grow while fixing carbon dioxide. I will discuss the genetic system we have developed for M. ferroxidans and how we are “domesticating” this bacterium to enhance growth under laboratory conditions.
Leveraging Synthetic Biology to Understand Environmental Bacteria
Synthetic Biology is traditionally applied to model systems such as Escherichia coli and Saccharomyces cerevisiae where new capabilities are added via introduction of new genes and pathways. Addition of new capabilities into environmental bacteria can be beneficial for learning about their metabolism and physiology and could be used to help domesticate some of the uncultured majority. Here I will describe how the introduction of proteorhodopsin helped us better understand metabolic energy flow in Shewanella and discuss our efforts to domesticate the bacterium Mariprofundus, an obligate iron-oxidizing chemolithoautotroph. Mariprofundus is the founding member of the zetaproteobacteria and produces a twisted iron oxide stalk as a necessary byproduct of its metabolism (it’s SO cool!).
Engineering Interspecies Electron Transfer
In our now aerobic world we often take for granted how easy it is to dispose of electrons from metabolic processes through the reduction of oxygen gas. However, for about the first billion or so years of life on our planet, oxygen gas was essentially absent from our atmosphere and oceans, yet microbial life thrived. Even today, anaerobic environments exist in sediments, the subsurface, in animal guts, in stratified lakes and oceans and industrial fermentations. In these anaerobic ecosystems, disposal of electrons is difficult and some organisms distribute this bourdon between partners. Here I will describe our efforts to synthetically construct a microbial co-culture system to explore molecular mechanisms of interspecies electron transfer using Shewanella and Geobacter.
Dale Warren Griffin, Ph.D., Waksman Foundation Lecturer
One of my favorite science activities is outreach through presentations and that can be in professional (the presentation of research findings) or public settings (public education and awareness talks, conference presentation/poster judging, regional and state science fair judging, etc.). I have previously served in ASM Branch officer roles (Secretary, President, etc.) for the Florida Branch and we always sought to promote undergraduate opportunities at our meetings. I also believe that mentoring is extremely important and have served as a mentor in the ASM Minority Mentoring Program in addition to the various postdocs, graduate student, undergrads and high school students (science fair projects) that I have helped guide through time. I’m often asked about post-graduate opportunities and what are the pros or cons of a government research position versus that of an academic. While it was quite some time ago, it seems like just the other day that I was asking the same types of questions – whether it was in the later phases of my M.S.P.H. or Ph.D. programs, or when standing at a career crossroad where competitive academic and government positions were offered to me (twice; once for postdocs and again later for permanent type positions). Information acquired through exposures to presentations and outreach programs and most importantly, mentoring, were fundamentally significant to my career decisions and development.
Lecture Topics and Descriptions
The Global Atmospheric Dispersion of Microorganisms by Desert Dust Storms
On a global scale, “desert-dust storms” move an estimated 3 - 5 x 109 metric tons of soil and dried sediment through Earth’s atmosphere each year. This presentation will cover the current state of knowledge of how dust storms disperse microbial communities and pathogens at global scales. Topics will include historical and current observations, methods of collection and analyses, implications and future research needs.
How Regional Geochemistry May Control the Distribution of Pathogens in Our Ecosystems: A Look at Bacillus anthracis in the Contiguous United States of America
Research indicates that Bacillus anthracis, while not endogenous to North America, is well established in certain regions of the contiguous United States. These groups of B. anthracis routinely cause outbreaks in livestock and wildlife and while rare, may cause human illnesses and fatalities. This presentation will cover historical and current research on this pathogen that has addressed how the geochemistry of our soils control its endemicity and how similar approaches may assist us in understanding microbial distribution in future research.
Antibiotic Resistance in Microbial Communities in Coastal Soils and Marine Sediments
Antibiotic resistance has recently been identified as an emerging environmental contaminant. Surprisingly few studies have been conducted to address natural background prevalence and prevalence due to anthropogenic sources in coastal and marine environments. The lack of knowledge regarding natural background prevalence in these environments limits our understanding of implications of their prevalence on both human and ecosystem health. This limit of knowledge also affects our ability to utilize prevalence to identify and mitigate potential sources (septic systems, outfalls, etc.) that can influence and sustain their occurrence. This presentation outlines our current state of knowledge of the presence of antibiotic resistance genes in microbial communities in these environments on both regional (sources such as wastewater impacted rivers and ocean outfalls) and large geographic scales (the coast of the NE United States).
Viruses and Our Quest for Extraterrestrial Life
Viruses are the most numerous entities and they are the primary drivers of evolution on our planet. In our quest for extraterrestrial life, viruses have largely been ignored. These entities are viewed as lifeless and individually specific to a given cellular life form. While many viruses are host specific (specific viruses) we know that some are capable of infecting multiple hosts (generalized viruses; e.g., influenza viruses, caliciviruses, coronaviruses, cucumber mosaic viruses). On Earth, we know that wherever you find cellular life, you find viruses. If we encounter cellular life on another planetary body, we are also likely to encounter viruses or virus-like entities that may be generalized in nature. This presentation will cover an overview on viruses (diversity, host specificity, beneficial and detrimental host relationships, survival outside the host, etc.), and why we should be looking for them in our quest for extraterrestrial life.
As a faculty member in the Arizona State University (ASU) microbiology program, I run an active research program, trying to understand how mammalian hosts protect themselves from poxvirus infection, and how poxviruses have evolved to evade host innate immunity. As such, we have identified a novel dual nucleic acid binding protein that allows vaccinia virus to evade sensing by the host innate immune interferon system. The thrust and parry that this system provides is an entertaining example of co-evolution between pathogens and hosts. One of the things I am most proud of about our research is how it is grounded in basic research, but has implications for benefiting humanity. My other passion is teaching. I truly enjoy seeing students and faculty get the message of my research. I have an open lecturing style, hoping to encourage discussion. Through my HIV prevention teaching, I have developed novel methods for teaching complex material to people who may not be experts in the field. I hope to bring this sensitivity to having every member of an audience understand my presentation to the ASM Distinguished Lecturer program. Having served as Director of the School of life Sciences at ASU, my commitment to student learning has broadened and deepened. That being said, serving as Director has limited the amount of time I have been able to devote to teaching. Having stepped down as Director, effective January 2019, I look forward to using more of my time for teaching, including serving as an ASM Distinguished Lecturer.
Lecture Topics and Descriptions
The Amazing, Death-Defying….Poxviruses
Poxviruses are among the most interferon-resistant viruses that have been characterized. The vaccinia virus E3L gene is essential for interferon-resistance. One of the main functions of E3L encoded proteins is to bind to and sequester the viral pathogen-associated molecular pattern (PAMP), A-form dsRNA. However, most poxvirus E3L–like genes encode a second nucleic acid binding domain, capable of recognizing Z-form nucleic acid. Our recent data demonstrates that this Z-NA binding domain of E3 proteins is essential for interferon-resistance, by inhibiting pre-mature program necroptotic cell death. This research provides insight into how cells sense virus-infection, and how viruses have evolved to evade sensing by the host.
Ancient Medicine/Modern Science: Re-discovery of Herbal Antivirals
Native Americans were reported in the mid-19th century to have an herbal cure for smallpox. We have gone back to characterize the herbal extract reported to cure smallpox. We have shown that this extract inhibits replication of vaccinia virus, monkeypox virus and variola virus, the causative agent of smallpox, and have begun to characterize the mode of action of this anti-viral extract. We have shown that this extract has antiviral activity against several unrelated DNA viruses, and may have efficacy both in humans and in animal models for treatment of viral diseases. These type of extracts may be a source of potential antiviral compounds.
From Basic Biology to Biomedicine: Transitioning Our Knowledge of Virus/Host Interactions into Potential Armaments in the Battle Against COVID-19
Treatment/prevention of COVID-19 must be based on our understanding of how viruses spread and how they interact with our innate immune system to cause disease. This talk will discuss how our knowledge of poxvirus pathogenesis can aid in the generation of safe, effective vaccines, and how our knowledge of virus/host interactions may provide clues to coronavirus pathogenesis, and provide potential leads for anti-coronavirus small molecules.
Over the past five years, I have become increasingly engaged in ASM with the goal of sharing my passion about microbial biodiversity while promoting cutting-edge science in this field. In addition to co-chairing the first retreat on Ecology, Evolution, and Biodiversity (EEB) in Washington, DC, I have served as a representative on the ASM Council on Microbial Sciences (COMS) and as the chair of the EEB Track. In this capacity, I have had a role in shaping the annual Microbe meeting, while building up a community through the organization of social gatherings and management of the EEB twitter account (@asm_eeb). I am eager to participate in the ASMDL program because EEB is the newest Track of science that is formally represented at ASM. While there is overlap with Applied and Environmental Science, interest in ecology and evolution is growing in allied fields including Host-Microbe Biology (HMB), Molecular Biology and Physiology (MBP), and Antimicrobial Agents and Resistance (AAR), in part, because of the transferable theory and tools that are being developed in our discipline. As a Distinguished Lecturer, I would be honored to share my vision of microbial diversity with a broad audience with the hope of inspiring microbiologists from all career stages and backgrounds about the ecology and evolution of complex microbial systems.
Lecture Topics and Descriptions
Evolution of the Minimal Cell
Synthetic biology is a branch of science that involves the redesign of biological parts, pathways, and modules. It has been used to generate working approximations of the minimal cell: an organism that only contains the essential genes needed for autonomous replication. But once such a cell is created, how does it contend with the forces of evolution, including mutation, drift, and natural selection? In this talk, I discuss the synthetic construction of the minimal cell (Mycoplasma mycoides) and the effects of genome streamlining using experimental evolution.
How Many Microbial Species Are on Earth?
In this lecture, I highlight patterns of microbial diversity compared to plants and animals. When abundance is accounted for, universal scaling laws emerge, which has allowed us to predict that there are one trillion (10^12) microbial "species" on Earth. I discuss genomic and evolutionary processes that may constrain the upper limit of species on the planet.
Microbial Seed Banks: Ecological and Evolutionary Importance of Dormancy
In this lecture, I introduce seed bank theory, which is based on the fact that organisms across the tree of life have evolved the ability to enter a reversible state of reduced metabolic activity; i.e., dormancy. I highlight theory and empirical studies showing how dormancy can be important for a range of evolutionary and ecological phenomenon including aging, pathogenesis, and the biogeography of microorganisms.
Eco-Evo Feedbacks in Microbial Communities
In this lecture, I discuss how rapid evolutionary change can modify ecological interactions with consequences for biodiversity. I focus on bacteria-phage interactions where host resistance and pathogen virulence coevolve, often exhibiting arms-race dynamics. Using marine cyanobacteria (Synechococcus) and soil bacteria (Bacillus), I emphasize how environmental factors (nutrient stoichiometry and energy limitation) alter evolutionary expectations based on changes in host physiology and dormancy.
I have been lucky to reach this level as a professor at a PUI (primarily undergraduate institution). As a first generation confused college student, and first in my family to become an academic, my learning curve was steep. After graduate school and postdoctoral work, I detoured into industry for nearly a decade, coming back to academia after more than a few struggles. Other than stubborn survival, what was “key” to my arriving at my current position?
To be succinct, it was interacting with people who listened to and encouraged me, who reminded me why microbiology was exciting, ever new, and the only profession for me. I can do that with my research students, but I would adore being able to reach out to graduate students to share microbial wonders, encouragement, and even a few words of advice. I think I have a solid view of student perspectives and have in fact sent many of my research students to Ph.D. programs and faculty positions.
As a Carski Awardee in 2018, I was recognized for success in undergraduate teaching and mentorship. I would argue that I am instead a fine “talent scout,” and able to share what I have learned with others. Yes, that includes my love of microbiology, and the topics I have described above. But what mattered the most to me was the personal approach, and I would very much like to “pay it forward” to other microbiologists on their own career paths.
Lecture Topics and Descriptions
Teaching Students to See with Microbial Eyes
In this updated version of my Carski Foundation Distinguished Undergraduate Teaching Award talk from 2018, I describe how to encourage all students in a microbiology classroom to embrace the depth and breadth and wonders of microbiology. This is done by describing fascinating new discoveries in microbiology, changes in perception of microbes, and ways to engage student interest and ownership via targeted assignments and artistic approaches. Success stories will be shared and celebrated!
Can Egg Laying Lizards Have Microbial Midwives?
I discuss my NSF supported (with Dr. Stacey Weiss) research that suggests that cloacal microbes in female striped plateau lizards may protect eggs against fungal and bacterial pathogens. This project bridges large data sets and microbial ecology with culture based work. Thus, it is ideal for taking undergraduate research students from the simple to the complex; from Kirby-Bauer plates to metagenomics and 16S analysis. Finally, it underscores the myriad critical roles that microbes play everywhere in the biosphere, including unexpected locations.
It’s a Germ-Eat-Germ World: Bacterial Predators on the Prowl
Once thought to be an odd exception in specific environments, bacteria that pursue and consume other bacteria appear more and more to be the rule in our microbial world. I discuss my own work with Bdellovibrio and Ensifer, as well as other fascinating microbial predators and their possible role in not only microbial ecology, but also medicine.
Using Artistic and Creative Approaches in a Science Classroom
One of the biggest challenges for educators is to encourage students toward enthusiasm and ownership in the classroom. I have found that encouraging students to create artistic representation of biological concepts can pay big dividends pedagogically, both in first year introductory biology classes as well as upper division microbiology. Specific examples and suggested strategies will be shared. Where possible I would like to include a #LuxArt session with this presentation, during which participants “paint” with luminous bacteria. I have put on many of these sessions, and they are well received and memorable.
I am interested in taking part in the ASMDL program because I not only have an interest in advancing methods in the public health and clinical microbiology laboratory but also in training the next generation of scientists to be inspired and excited by contributing to this important field. In my 20 years of public health experience, I have mentored more than 35 students and training fellows and I have worked to improve and build training and educational programs to support these students, fellows and postdocs at the Wadsworth Center, NYS DOH (New York State Department of Health). Contributions have included coordinating a NYS fellowship program, teaching and mentoring as a SUNY Albany Biomedical Sciences Assistant Professor and contributing to the Wadsworth Center Master’s Degree in Laboratory Sciences program as a faculty member, committee chair and mentor.
I was fortunate to have received an Association of Public Health Laboratories and Centers of Disease Control (APHL/CDC) Emerging Infectious Diseases (EID) Fellowship early in my career which impacted my training and opportunities and launched my career in public health. My goals are to provide similar opportunities to those interested in exploring or pursuing a similar path. I would welcome additional opportunities to meet with and motivate students, fellows and postdocs through the ASMDL program.
Lecture Topics and Descriptions
Superbugs Among Us: New Tools and Strategies to Combat Antimicrobial Resistance
A description of antimicrobial resistance with an emphasis on carbapenem-resistant Enterobacteriaceae (CRE) will be provided along with new national prevention efforts, new methods (e.g., whole-genome sequencing) and new strategies to prevent the spread of these highly resistant pathogens in healthcare facilities.
Unraveling the Genomes of Bacterial Pathogens: Next-Gen Approaches
This talk will discuss the utilization of next generation sequencing methods including amplicon-based NGS, whole-genome sequencing and other available sequencing approaches. It will focus on public health diagnostics and surveillance for providing comprehensive characterization of bacteria to impact patient management as well as its important contribution to outbreak investigations, with an emphasis on activities at the New York State Department of Health’s Wadsworth Center.
The Future Is Here: Next Gen Sequencing for TB
Whole-genome sequencing (WGS) of Mycobacterium tuberculosis is a new method providing unparalleled genetic information impacting treatment cases of tuberculosis (TB). This new method provides a prediction as to whether the patient can be effectively treated with a typical drug regimen or whether there is antimicrobial resistance to any of eight drugs utilized for TB. Additionally, WGS analysis is also contributing to preventing the transmission of this significant worldwide pathogen. A discussion of how this testing works, how the method was developed and the validation of the method as a diagnostic test at the Wadsworth Center in New York.
Inside a Legionnaires’ Disease Outbreak Investigation
A description of available test methods and more than 40 years of experience testing patient and water samples for this pathogen will be discussed. A historical perspective of improvements in testing and outbreak investigation since the Philadelphia outbreak in 1976 will be presented, along with past to recent outbreaks and stories from these investigations including New York State’s approaches and experiences.
I am pleased to be chosen as an ASM Distinguished Lecturer because it is a way to communicate my enthusiasm for bacteriology-related research and pay back the research community for all the opportunities that I received as a student and postdoc. I have always placed considerable emphasis on the training and mentoring of graduate students and postdocs. I feel comfortable stating that it is the most important and gratifying aspect of my career. My former trainees are now completing postdoctoral fellowships in highly recognized laboratories, have returned to medical school as part of a dual degree program, or after completing a successful postdoc have successfully made the transition to junior faculty. I have always felt that faculty have the responsibility to inspire and empower their trainees; in brief, to give them every opportunity to succeed. Along such lines, I promote strong lines of communication, personal responsibility for one’s success, and goalsetting, and feel that highlighting the positive is an essential aspect of constructive commentary. I feel that I am qualified to be an ASMDL lecturer due to the strength of my research program, my experience in promoting the development and success of trainees, and what I feel is a positive message in regards to meeting the challenges of a career in science head on.
Lecture Topics and Descriptions
Holes in Your Heart During Pneumonia? Dissecting Pneumococcal Cardioxicity
One quarter of individuals who are hospitalized for community-acquired pneumonia experience an adverse cardiac event: heart failure, arrhythmia, and infarct. These individuals are four times more likely to die than those with pneumonia alone. Research in our laboratory has shown that Streptococcus pneumoniae, the leading cause of community-acquired pneumonia, is able to escape from the bloodstream and invade the heart. Within the myocardium, pneumococci replicate, kill cardiomyocytes, form biofilms, and disrupt cardiac contractility. Laboratory animals that survive these types of infection experience cardiac scarring and impaired heart function thereafter. This talk describes the incidence of cardiac complications during pneumonia, the morphogenesis of cardiac microlesions, the virulence determinants identified as being responsible for pneumococcal invasion of the heart and killing of cardiomyocytes, and the approaches towards prevention currently being explored.
Pneumococci Have a Sweet Tooth: Carbon Availability Influences Pneumococcal Virulence
In most instances, Streptococcus pneumoniae colonizes the nasopharynx asymptomatically. Yet within the lungs, S. pneumoniae elicits a robust inflammatory response that contributes to lung damage and lung consolidation. Over the past 10 years, our laboratory has demonstrated that carbon availability, principally the absence of glucose, directly influences the ability of S. pneumoniae to form biofilms and the virulence determinants that it produces. This talk describes anatomical site-specific differences in carbon availability within the host, how the bacterium adapts to the nutritional differences in these distinct niches, the in vivo core transcriptome and tissue-specific transcriptome of S. pneumoniae as determined using dual-species RNAseq of infected organs, and how this information informs on the pathogenic process of the pneumococcus as well as rationale antigen selection for the next generation vaccine.
Pore-forming Toxin Mediated Cell Death: A Role for Necroptosis
Pore-forming toxins are the most common virulence determinant used by pathogenic bacteria to kill host cells. Until recently, it was thought that pore-forming toxins killed via the membrane damage they incurred, and this resulted in necrosis; i.e. the loss of membrane integrity. Recent results from our laboratory have changed this understanding and shown that host cells exposed to pore-forming toxins instead die of necroptosis, a programmed mode of cell death that resembles necrosis. Moreover, much of the damage incurred by pore-forming toxins may be prevented by blocking the signaling molecules that regulate the necroptosis pathway. This talk describes how bacterial pore-forming toxins non-canonically activate necroptosis. It overviews the beneficial effects of necroptosis; e.g., how it promotes development of an adaptive immune response to pore-forming toxin producing bacteria during asymptomatic colonization, as well as the detrimental; e.g., exacerbated pulmonary injury during bacterial pneumonia. The talk concludes with discussion of how pharmacological inhibition of necroptosis may serve as an adjunct therapy for infectious diseases involving Gram-positive bacteria including invasive pneumococcal disease that results in heart damage.
It is a great honor to be chosen to participate in the ASM Distinguished Lecturer Program. Clinical microbiology is rapidly advancing with an abundance of novel technologies that are revolutionizing the diagnosis of infectious diseases. As a clinical virologist, I have developed and translated infectious diseases diagnostics into clinical practice with the ultimate goal of improving patient care in both high- and low-resource settings. The ASMDL program provides a tremendous opportunity to review diagnostic dilemmas and share impactful translational science with the ASM membership. I am particularly excited to share my experiences collaborating with partners from low- and middle-income countries to develop and implement diagnostics for emerging and re-emerging infectious diseases.
I have a track record of commitment to training the next generation of clinical microbiologists. I have taught the principles of diagnostic virology to trainees of all levels locally, nationally, and internationally. Furthermore, I have successfully mentored several individuals to achieve positions in academia and public health. For example, Dr. Jesse Waggoner, a prior infectious diseases fellow, obtained a National Institutes of Health K08 Mentored Clinical Scientist Research Career Development Award under my mentorship, and is now an Assistant Professor at the Emory University School of Medicine. Dr. Janaki Abeynayake, a trainee from Sri Lanka, is now the Head of Virology at the Medical Research Institute in Colombo, the Sri Lanka National Reference Laboratory for Infectious Diseases.
I have been a member of ASM since 2009 and spoke at the Pediatric Microbiology for Clinicians and Laboratorians workshop prior to the General Meeting/Microbe from 2015-2017. I am completely committed to ASM and to the training of clinical microbiologists/virologists. Through the ASMDL program, I intend to continue this commitment by detailing the challenges and opportunities of this rapidly evolving field.
Lecture Topics and Descriptions
Testing for the Diagnosis and Monitoring of COVID-19
The COVID-19 pandemic has revealed the global importance of robust diagnostic testing to differentiate SARS-CoV-2 from other routine respiratory infections and guide appropriate clinical management. This presentation details the nucleic acid amplification and serologic methods that are available to diagnose and monitor SARS-CoV-2 infections.
Adventures in Arbovirus Diagnostics
Arthropod-borne viruses are among the most important emerging infectious diseases. Based on clinical criteria alone, arboviruses, such as Zika, dengue, and chikungunuya viruses, cannot be reliably distinguished from one another or infections with other pathogens that cause an undifferentiated systemic febrile illness. This presentation details the molecular and serologic methods that are available to diagnose arbovirus infections.
Next-generation Sequencing for Antiviral Resistance Testing
The development of drug resistance is an important factor in the management of clinically significant viral infections, particularly HIV-1. Genotypic drug resistance testing by conventional Sanger sequencing has limited sensitivity for low-frequency drug resistance mutations, whereas next-generation sequencing (NGS) methodologies allow the detection of minority variants associated with virological failure. This presentation focuses on the clinical application of NGS to genotypic antiviral resistance testing.
Infections acquired in utero and during the perinatal period are important causes of fetal and neonatal mortality and morbidity. These infections present with similar signs and symptoms, and therefore, diagnosis is challenging and relies on accurate laboratory testing. This presentation utilizes a case-based approach to detail the diagnosis of TORCH infections.
Virologic Monitoring in Transplantation
Viral infections are important causes of morbidity and mortality in both solid organ and hematopoietic cell transplant. Virus load monitoring of several viruses, including CMV, EBV, and BKV, are critical for the optimal management of the transplant recipient. This presentation reviews transplant virology, including assay harmonization to the WHO international unit, as well as novel monitoring approaches combining host response with virus quantitation.
Throughout my career, I have had great mentors, notably my Ph.D. advisor who supported me and instilled in me a commitment to train the next generation of microbiologists. To support women and URM interested in research, I currently participate in programs that range from hosting all-girls high school students to discuss opportunities for careers in science to mentoring summer undergraduates through the OHSU Center for Diversity and Inclusion internship program. In my roles as the program director of the Molecular Microbiology and Immunology (MMI) Ph.D. program and the new interdisciplinary Program in Biomedical Science (PBMS) Ph.D. program, I am keenly aware of the role of mentors in successful graduate training and in finding rewarding careers. One of the exciting aspects of PBMS is its inclusion of research, academic and peer mentors to strengthen the graduate training experience. Through the ASMDL program, I will contribute more broadly to the development of future scientists through meaningful interactions at Branch meetings. As a PI who is still “in the trenches” doing experiments, I look forward to sharing my excitement about science with trainees and discussing their career goals and aspirations. I have been an active ASM member since 1999 and routinely attend ASM meetings. I was an invited speaker at the ASM Tuberculosis Conference and the Northwest Branch meeting in 2017 and hosted the Northwest Branch Meeting at OHSU in 2018. Being part of the ASMDL program will provide new opportunities for me to contribute to ASM’s mission of advancing the microbial sciences.
Lecture Topics and Descriptions
The Big Ball of Wax: The Role of MmpL Transporters in Mtb Cell Wall Biosynthesis, Virulence and Non-replicating Persistence
TB is a leading infectious disease that causes death despite the availability of anti-tubercular drugs. The MmpL transporters make a crucial contribution to mycobacterial physiology and pathogenesis by exporting cell wall lipids to the mycobacterial outer membrane. This talk will describe the role of the essential MmpL3 transporter in cell wall biogenesis and show the contribution of MmpL11 to virulence and non-replicating persistence.
Why Microbiologists and Structural Biologists Should Be BFFs – Structural Insights into Mtb Cell Wall Biosynthesis and Drug Development
The MmpL proteins are cell wall lipid transporters and include crucial contributors to mycobacterial physiology and validated drug targets. Despite the importance of MmpL proteins to Mtb, little is known about their structure and the mechanism by which they transport complex lipids or molecules to the bacterial surface. While MmpL proteins are members of the resistance-nodulation-cell division (RND) superfamily of proteins, recent structural and biochemical studies have shed light on their unique structures and novel transport activities.
Are You Awake? New Insights into Mtb Metabolism and Physiology During Latency
TB is a leading infectious disease that causes death despite the availability of anti-tubercular drugs. Most Mtb infections result in latent TB where bacteria have altered metabolism and exhibit phenotypic drug tolerance. This talk will review current in vitro and in vivo models for Mtb latency and the insights gained.
Pathogens often win the initial battle (and sometimes the war) against us despite our arsenal of antimicrobial effectors and trillions of commensal microbes. How can this happen? This is the question that I have been asking myself since medical school in Italy, and have been trying to answer with my research. Shortly after completing my medical training, I took a one-way ticket to the United States, where I have been working on host-microbe interactions for the past 16 years. Throughout this time, I have been a member of the American Society for Microbiology, and an author in and a reviewer for ASM journals. More recently, I began serving as an Editor for Infection and Immunity. I am thus deeply committed to the success of ASM, and I am honored to be part of the ASM Distinguished Lecturer program and to speak at ASM Branch meetings all over the country. I am particularly committed to mentoring new generations of scientists, which is one of the most rewarding activities of my profession. I greatly look forward to interacting with and informally mentoring students and post-docs at ASM Branch meetings. Furthermore, as a woman in science, my hope is to inspire other women to pursue a fulfilling scientific career in academia.
Lecture Topics and Descriptions
Guts, Germs, and Steel: The War for Metal in the Inflamed Gut
Obligate anaerobes (Firmicutes and Bacteroidetes) predominate in the normal gut. However, Proteobacteria expand in the inflamed gut by successfully competing for limited resources. This lecture will present mechanisms by which pathogenic and commensal Enterobacteriaceae compete for metal ions in the inflamed gut.
Nutritional Immunity in the Inflamed Gut
In response to infection with enteric pathogens that cause inflammatory diarrhea, such as Salmonella Typhimurium, the host mounts a response termed nutritional immunity, which limits the availability of essential metal ions including iron, zinc, and manganese. This lecture will discuss the host cytokines that regulate nutritional immunity, and will outline the roles of two antimicrobial proteins, lipocalin-2 and calprotectin, in sequestering metal ions during colitis and their effects on gut pathogens and on the gut microbiome.
Mucosal Responses to Salmonella Infection
The gut pathogen Salmonella Typhimurium is one of the leading causes of inflammatory diarrhea worldwide. This lecture will discuss the pathogenesis of Salmonella Typhimurium infection in the gut, with a focus on the host responses that are protective during infection and keep the infection localized to the gut, thereby preventing bacteremia.
Learning from Bacterial Competition in the Host to Develop New Antimicrobials
In recent years, the alarming increase of antibiotic resistance has created serious concerns for public health. Moreover, current antibiotics also target the beneficial gut microbiome. This lecture will discuss what can be learned from investigating microbial competition in vivo and how this knowledge can be utilized to devise new narrow-spectrum therapeutics that target bacterial pathogens while minimizing deleterious effects to the microbiome.
Marilyn C. Roberts, Ph.D., Waksman Foundation Lecturer
Dr. Roberts is a long time member of ASM and fellow in AAM (American Academy of Microbiology). She has demonstrated particular capability to lecture about antibiotic resistant bacteria/genes to audiences that have limited backgrounds on the subject. She believes it is important to educate people on this important subject and has completed a video lecture for ASM on the topic. Being part of the ASMDL program will provide another opportunity of reaching more people that are learning about microbiology but may have limited knowledge about antibiotic resistant bacteria or the One Health Concept. Education of a wider group of citizens is one way to help be part of the solution to slow the use of antibiotics in both humans and agriculture and, hopefully, reduce or stop the dramatic increase in antibiotic resistance seen locally, nationally and internationally.
Dr. Roberts has often been asked by journalists to provide insight into her specific research, as well as what the community can do to try and reduce the use of antibiotics and related compounds, such as tricolsan, in their lives so that the world does not end up in a “post antibiotic era” – a time when few antibiotics are available for treatment and those that are available are very expensive.
Dr. Roberts is committed to teaching and mentoring students. She has trained more than 90 undergraduate students, some of whom have been authors on papers which helped them secure very good jobs upon their graduation. She has also trained a number of graduate students who have found jobs in university settings, industry or state agency laboratories.
Lecture Topics and Descriptions
One Health Approach to Multidrug Resistance MRSA in Primates, Humans and their Shared Environment
This lecture discusses how a single strain of MRSA was passed from primates to personnel and their environment or from humans to wild primates in different settings including Nepal and a National Primate Research Center.
Why a One Health Approach is Important to the Understanding of Transmission of Antibiotic Resistant Bacteria and Resistance Genes throughout the World
This lecture looks at different resistant pathogens and examines how people, animals and their shared environment affect how they have spread. One example is vancomycin resistant Enterococcus spp. spread in the USA vs Europe.
Antibiotic Resistance and Foodborne Outbreaks
This lecture discusses how antibiotic resistance bacteria are linked to antibiotic use or environmental contamination in food animals, leading to foodborne outbreaks with antibiotic resistant pathogens.
Wild Animals as Vectors for the Spread of Antibiotic Resistant Bacteria and Genes through Different Environments Locally, Nationally and Internationally
This talk discusses how birds and other wildlife can spread and contaminate environments with specific human pathogens and influence potential risk to man.
During my graduate and postdoctoral training, I was fortunate to find mentors that supported my scientific and career development and allowed me the opportunity to pursue my research interests. I have also benefitted from sponsors that have advocated for me along the way. To pay it forward, I promote tailored training and mentoring of undergraduate, graduate, and postdoctoral scientists –not only in my own lab, but at UNC and elsewhere. In fact, one of my favorite aspects of giving seminars at other institutions is the opportunity to interact with students and postdocs, learn about their science, aspirations, and concerns, and frankly discuss my own experiences. As an ASM Distinguished Lecturer, I would love to continue these interactions to pass on my passion for research and mentoring and to share insights I’ve gained during my career. Since 2009, I have mentored 11 undergraduates, four post-baccalaureate fellows, five Ph.D. students, and four postdocs. I am a frequent discussion leader for graduate and postdoctoral scientists, including topics in research program and lab management, academic career development, and issues affecting the well-being of our trainees. I am also a mentor for UNC’s Initiative for Maximizing Student Development (IMSD) program, allowing me to interact with a diverse graduate student population and support their career and personal development. I am a member not only of ASM, but also the Society for the Advancement of Chicanos and Native Americans in Science (SACNAS).
Lecture Topics and Descriptions
A Bacterial Lifestyle Switch: The Role of Riboswitches in Behaviors and Virulence of Clostridium difficile
As in many other bacterial species, c-di-GMP controls the switch between motile and non-motile lifestyles of C. difficile. In addition, C. difficile has incorporated c-di-GMP signaling to regulate the production of the cytotoxins required for virulence. This talk describes our work to identify the processes regulated by c-di-GMP in C. difficile and the mechanisms by which regulation is achieved. Unlike most species studied to date, C. difficile uses riboswitches to sense intracellular c-di-GMP and mediate the appropriate behavioral response.
When a Clone Is Not a Clone: The Case of Clostridium difficile
Work from the Tamayo lab recently revealed that in C. difficile, swimming motility, toxin production, and other factors are subject to phase variation through site-specific DNA recombination. This phase variation involves the reversible inversion of DNA sequences that impacts the expression of adjacent genes and results in considerable phenotypic heterogeneity in the population, with individual bacteria exhibiting variable phenotype profiles. This talk summarizes these studies and discusses the implications of phase variation and phenotypic heterogeneity in the survival and virulence of the C. difficile population as a whole.
Intersecting Paths to Phenotypic Heterogeneity
Phase variation in bacteria typically controls the ON/OFF production of individual factors exposed on the bacterial surface. In the case of C. difficile, phase variation regulates the expression of transcription factors and enzymes controlling c-di-GMP levels. This talk discusses these studies and the potential for these phase variation mechanisms to broadly impact C. difficile gene expression, physiology, and virulence.
The Power of Bacterial Genetics for Elucidating Molecular Mechanisms
The mechanism of flagellar phase variation resulting from DNA inversion is unusual, occurring at the mRNA level. This talk describes our use of a suppressor analysis to identify the factor involved in mediating regulation – a well-known protein with an unexpected function.
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