Allison Cartwright is our ECS Publications Officer. Here, she looks at the fascinating survival of frozen bacteria.
As Christmas nears and we dream of snow and ice (currently seen from my window!), I can’t help but wonder, what amazing microbes would you find in ice? Having studied marine science, we had a lecture dedicated to the polar sea and learned that bacteria can survive in ice.
At the time, my concern was for how dolphins and whales were affected by ice as they searched for breathing holes, so failed to hear about the microbes. Now my interests have shifted, I want to know what’s in the ice and how these microbes survive in the cryosphere?
The harsh environment of ice means bacteria are found in lower abundance than soil or water in temperate regions, but they aren’t devoid of microbes. Bacteria found in ancient ice include Pseudomonas and Acinetobacter, which are widely found in un-frozen areas too.
Fresher ice samples include bacteria species such as Pseudomonas fluorescens and Marinomonas protea. As these microbes aren’t ice specialists, how do they survive?
Force of nature
Many bacteria are undoubtedly killed by ice, either from crystals bursting their cells as the ice expands, or from the sheer force of the ice. The UK and Ireland have many landscapes formed by the sheer pressure of ice quite literally ‘moving mountains’.
With this kind of pressure, what hope do microbes have against this force? They are likely to be destroyed. But inside the hostile ice environment are little oases – usually warmer air pockets or channels of liquid water. In these warmer habitats bacteria can continue with natural life-processes, seemingly unaware of the hostile world surrounding them.
Old and cold
Even in ancient ice, aged at 750, 000 years old, bacteria were recovered. 14 amazing isolates not only stood the test of time, but survived freezing temperatures and the crushing force of subsequent ice layers formed in later years.
Part of their survival could be linked to the ability of some microbes to carry out metabolic processes to temperatures of -40 ℃ and even repair their DNA at -15 ℃. This adaptation is partly reliant on a special antifreeze protein released by some bacterial cells to prevent the formation of ice crystals.
Frozen in time
Bacteria are even found in the water and sediment at the bottom of Antarctica’s lakes which have permanently frozen surfaces. They can survive by entering a dormant state where they wait patiently to be freed from ice allowing them to grow again.
This allows microbes to survive for a few hundred thousand years. Of course, we cannot fully understand the survival strategies these clever microbes use as this time-scale extends well beyond our scientific records, and indeed the time in which Homo sapiens have existed.
Bacteria can survive in colder temperatures than that found in Polar ice. As I moved into the microbiology world of research, I was amazed when a colleague took me to a -80 ℃ freezer to get some stock bacteria.
It still surprises me that bacteria can lie dormant and survive these temperatures. I would probably only survive these temperatures in a timescale of minutes, but the bacteria inside me could survive hundreds and thousands of years. As I bravely sit out the ice inside a nice warm house, I can’t help but wish I was a bit more like the special microbes adapted to survive freezing conditions.
Brown, P. (2013). Colder than ice: Researchers discover how microbes survive in subfreezing conditions [Online]. Available from: https://blogs.scientificamerican.com/guest-blog/colder-than-ice-researchers-discover-how-microbes-survive-in-subfreezing-conditions/ [Accessed 3 December 2017].
Christner, B. C., Mosley‐Thompson, E., Thompson, L. G., & Reeve, J. N. (2003). Bacterial recovery from ancient glacial ice. Environmental Microbiology, 5(5), 433-436.
Gilbert, J.A. et al., 2004. Demonstration of antifreeze protein activity in Antarctic lake bacteria. Microbiology, 150(1), 171–180.
Categories: Feature Articles