Episode Summary

Christine Foreman explains how microbes can survive and grow on glaciers, and what we can learn from microbes in glacier ice cores.

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Julie’s Biggest Takeaways

Liquid inclusions between ice crystals create a vein-like network that allow microbes to survive between the ice crystals.

Microbes living in glaciers have to adapt to a number of extreme environments: low water, low nutrients, extreme cold, and 6 months each of full sun or complete darkness mean there are many adaptive requirements to live in glaciers.

Air bubbles trapped in ice cores provide data on the atmosphere 40,000 or 100,000 years ago. Using very old samples like these can inform scientists about the precipitation, temperature, and major cataclysmic events that occurred at those time periods.

Because so many researchers share ice core samples, a research group like Foreman’s will often get a very small sample, as low as 7 ml, for a particular time period. Given that there are only 100 to 10,000 cells per ml, that is not a lot of sample to work with!

Aggregation of life, including microbial biofilms, changes the absorption of solar radiation. A clear, white surface radiates back as much as 90% of the solar radiation, but as aggregates form, they allow more of the solar radiation to be trapped. This in turn can increase microbial metabolic activity and allow even more microbial growth, leading to a feedback loop that increases absorption of solar energy and loss of glacial surfaces.

Featured Quotes

“A lot of [glacial] organisms are transported in the atmosphere. Depending on prevailing winds, they may be coming from an environment that is much more temperate than where they are landing.”

“Any chance you can to be in the environment in which your samples are coming from gives you a much broader understanding of what it is that they face.”

“Glacier cores are essential our museums back in time.”

“We’re interested in understanding the quality and quantity of dissolved organic matter within ice, because that helps us understand some of the constraints on the organisms that can live there.”

“You can solve much more complex problems by having diverse perspectives!”

“If you want to understand what is happening at the systems level, you have to understand the microbes.”

Links for This Episode

History of Microbiology Tidbit

Many of the millennia-old organisms that date back to the time periods discussed on this epsiode were found in the aughts. Some of these are ultrasmall bacteria, such as Chryseobacterium greenlandensis or Herminiimonas glaciei, both discovered in ice cores from Greenland that date back 120,000 years. The very first ultra-old bacteria was discovered in Alaska, however, from a tunnel dug by the Army Corps of Engineers in the 1960s, built in preparation for the construction of the Trans-Alaska pipeline system, a huge crude oil pipeline. The tunnel, called the Cold Regions Research and Engineering Laboratory, wasn’t part of the pipeline, but was built so that the engineers could learn the characteristics of the permafrost and properly design and build the actual pipeline.

It wasn’t until the late 1990s that Richard Hoover, a scientist working for NASA, began looking at the exposed permafrost for signs of life. NASA’s interest in extremophiles in these cold regions stems from their interest in probing mars for signs of life — one can imagine the excitement of finding *signs* of microbial life that can live in the extremely dry, extremely dark, nutrient depleted conditions, conditions that mimic those found on our neighboring planet. The fact that the microbes themselves could be revived and continue growing after millenia of dormancy only boltered the idea that life may exist even in this extreme environment.

Hoover and his collaborator Elena Pikuta grew the bacteria in anaerobic conditions, which is different than the way that Christine grows her samples, and they called it Carnobacterium pleistocenium, with the species name clearly called so after the epoch in which it originated. Hoover himself cautioned that this discovery does not guarantee life on Mars, and is quoted as saying “The existence of microorganisms in these harsh environments suggests — but does not promise — that we might one day discover similar life forms in the glaciers or permafrost of Mars or in the ice crust and oceans of Jupiter’s moon Europa.” These are the most promising places in our solar system to find life, outside of Earth of course, because they contain water, which is almost certainly essential for life.

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