In Memoriam: Castenholz, Richard W.

In Memoriam: Castenholz, Richard W.


Richard “Dick” Castenholz died Thursday April 19, 2018 due to complications during surgery. He was 86. His unexpected passing marks the end of an era in microbial phototroph research that spanned seven decades, during which Dick deservedly gathered many honors, including: J.S. Guggenheim Fellow (1970-71), Fulbright Scholar (1977-78), Fellow AAAS, Trustee, Bergey’s Manual Trust (1991-2001), Fellow, American Academy of Microbiology (1996-his death), Bergey Medal for Distinguished Achievement in Bacterial Taxonomy, and American Society For Microbiology 2009 USFCC/ J. Roger Porter Award for studies of microbial diversity. Dick was a long-time ASM member.

Dick’s remarkable research journey began with his Ph.D. graduate work at Washington State University, training as an algal ecologist, and focusing on the ecology of diatoms in the Grand Coulee. After his appointment as an Assistant Professor at the University of Oregon, he started studies on marine diatoms, but soon moved to the study of the microbial ecology of terrestrial hot-springs. He soon became the world expert on thermophilic phototrophs, and a towering figure in Yellowstone National Park research. In parallel, based on his evolving interests and the influence of key colleagues, such as Bill Sistrom and Roger Stanier, blue-green algae became to be recognized as bacteria (cyanobacteria) and resulted in their inclusion in the International Code of Nomenclature of Bacteria.

Dick moved rapidly through the academic ranks to that of Professor. He “retired” in 1999 but continued to work in the lab, the field and the classroom, until the very day before his passing. Over the years his work was supported by 26 National Science Foundation awards and 9 additional grants from the National Aeronautics and Science Administration. In total, he authored or co-authored 156 publications.

Dick had many attributes that contributed to his scientific and mentoring skills. First, and foremost, was his power of observation. He could recognize individual microbes and relationships in field micro- and macroscopic observations that most all of us miss. Attempts to explain to him what one observed was humbling, especially when he was looking at the same sample or site. Dick had a phenomenal memory for many events, facts and, especially, the algal, bacterial and cyanobacterial systematic and ecological literature. For those who knew him well, it was always astonishing that he could remember and find papers stacked high on his desk. He was highly dedicated to his culture collection, isolating strains, transferring cultures that would lose viability upon freezing, even at liquid nitrogen temperatures, and making sure the collection was an international resource. It is highly fortunate the Pacific Northwest National Laboratory agreed to house and maintain his collection of environmentally extreme cyanobacteria and algae.

Dick’s dedication to microbial ecology was infectious and, together with his observational skills, fostered his mentorship powers. His research program was conducted with undergraduate and graduate students, as well as international visitors. He recruited and trained 31 graduate students. Dick treated all students with respect and gave them the degree of independence they might have desired; his mentorship was always subtly different, dependent on his observations or requests from students. He was an extraordinarily successful mentor; his graduate students have gone on to successful careers as scientists in government, industry and academics that could not necessarily be accounted for by their initial analytical, experimental or communication abilities.

His research accomplishments are too numerous to detail, but often they were ahead of their time. For example, to him we owe a focus on strain variability in physiological capacities within populations, a phenomenon re-discovered several decades after his initial publications as “population microdiversity.” Similarly, he described astonishing continental-scale biogeographical patterns of microbial distribution in hot-springs well before the renaissance of this concept in the first decade of the millennium. He made seminal contributions to the physiology of cyanobacteria, particularly on their adaptations to extremes of temperature, salinity, visible and UV light, and hydrogen sulfide, and to the the motility responses mechanism that those parameters elicit. Importantly, he contributed greatly throughout his career to the description of novel microbial phototrophs, the discovery of the Phylum Chloroflexi being perhaps the best known, and to “ trying to unravel the confusing taxonomy and classification of cyanobacteria,” penning classical contributions to the Bergey's Manuals.

Dick was a kind, thoughtful man. Beyond science, he enjoyed sailing, bird watching, classical music, and poetry. He generously supported civil and animal rights groups, environmental causes, and the arts. His wife of 36 years, Phyllis, his son, Ralph, and his grandson, Josef, survive him. His son, Reave, and his brother, William, preceded him in death. He also leaves behind many friends, a large cohort of mentees, and his beloved dogs.
Obituary By:
  • Ferran Garcia-Pichel, Arizona State University
  • Steve Giovannoni, Oregon State University
  • Tim McDermott, Montana State University
  • Jack Meeks, University of California - Davis
  • Scott Miller, University of Montana