Antarctica is one of the driest, coldest places on Earth. Very little life survives its extremes.
Authors
- Yongyi Peng
PhD Candidate in Environmental Microbiology, Monash University
- Ry Holland
Research Fellow in Microbial Ecology, Monash University
In the soils dotted around the frozen ice sheets, however, communities of microbes do survive. And one of the keys to their success is a surprisingly communal strategy.
Unrelated organisms share the tools for survival by transferring genes among themselves, including genes that allow them to make energy from the air itself.
In new research, we studied the genomes of 676 microbe species and discovered that almost all of them (around 98%) showed evidence of swapping genes with other microbes. The study is published in Nature Communications.
Energy from the air
Our findings suggest this process, known as horizontal gene transfer, is a key to Antarctic microbe survival.
Genes involved in energy production were among the most frequently transferred. In particular, the genetic tools that allow microbes to generate energy from atmospheric gases, a process known as " aerotrophy ", were very commonly shared. This is probably because they help microbes harvest scarce resources from their harsh environment.
Aerotrophy allows microbes to use tiny amounts of gases in the atmosphere, such as hydrogen and carbon monoxide, as an energy source.
In most environments, aerotrophy is like a backup generator, allowing bacteria to survive when other resources such as food and sunlight are scarce.
But in Antarctica, it seems to be needed for everyday survival. The genes have been repeatedly passed between different and distantly related microbial species.
How do microbes share genes?
Imagine having the superhuman ability to make food from thin air and then randomly sharing it with some of your neighbours. While humans don't work that way, microbes sometimes do.
Horizontal gene transfer is kind of like randomly airdropping bits and pieces of your genetic code to those around you, whether you're related or not. It's a useful way to gain new capabilities that may provide an advantage in challenging environments.
Humans only pass genetic information to their offspring, through what is known as vertical gene transfer. But horizontal gene transfer in microbes can happen in three different ways.
The first way is by scavenging free DNA in the environment, usually from dead cells. The second is by receiving DNA through microscopic bridges temporarily established between microbial cells. And the third way is via infection by a virus that accidentally brings some of its last host's DNA along for the ride.
Microbes can acquire genes, but nature decides which ones stay
Adding a new genetic tool is only the beginning. After a microbe acquires a new gene, that gene must prove useful in its new host.
In microbes, if the transferred gene provides an advantage, it quickly becomes established throughout a population via natural selection. This process also weeds out harmful transfers.
Over many generations, small changes naturally appear in genes. For genes that provide important survival benefits, such as aerotrophy, changes that preserve their function are more likely to be maintained. Genes that no longer provide an advantage are gradually lost.
This process acts like a long-term quality check. Microbes can gain new abilities through gene exchange, but only the genetic tools that continue to improve their survival odds are kept. This helps explain why we continue to find the same energy-generating genes in distantly related Antarctic microbes, even across locations separated by thousands of kilometres.
Living off air underpins terrestrial Antarctic life
Aerotrophy appears to have helped Antarctic soils sustain diverse communities of microbes that play essential roles in Antarctic ecosystems. These microbes drive the flow of nutrients and energy through the ecosystems.
As Antarctica undergoes rapid environmental change, these microbial processes are also increasingly important to understand. Warming temperatures can alter microbial activity, potentially affecting the important processes that sustain these ecosystems.
Understanding how Antarctic microbes survive and respond to environmental pressures will give us new insights into how this ancient ecosystem might respond to warming.
Beyond their ecological roles, these microbes also challenge the way we think about Antarctica. Rather than an empty white continent, Antarctica harbours somewhat hidden but highly adaptable ecosystems filled with microbial life. These tiny survivalists have evolved strategies to endure some of the harshest conditions on Earth, including extreme cold and dryness, prolonged winter darkness, and nutrient scarcity.
By understanding how these microbes survive, scientists can learn more about the fundamental limits of life itself. Those insights could help us understand how organisms might survive in other extreme environments, including on future space missions or even on icy worlds beyond Earth.
Yongyi Peng receives funding from Monash University through the Monash Graduate Scholarship (MGS) and Monash International Tuition Scholarship (MITS).
Ry Holland is a Research Fellow at Monash University funded by the Australian Research Council Special Research Initiative 'Securing Antarctica's Environmental Future' (SAEF) and an Australian Antarctic Division project grant.
