In lava tunnels, where living conditions are similar to the ancient Martian environment, biologists have been able to identify microbial life forms. They are very varied, and their interactions are complex, whereas these conditions do not seem to allow it.
One would imagine that in lava tubes and geothermal vents, the conditions are not conducive to an abundance of life. This is also what biologists postulate. And yet, a newly published study in Frontiers in Microbiology demonstrates the opposite. In this work, the researchers highlight a whole microbial diversity that was still unknown.
The authors took 70 samples from the heart of different volcanic sites in Hawaii, where the conditions are the harshest for living things. They then sequenced the ribosomal RNA to identify the bacteria present, their diversity and their abundance. The results show high quantities, as well as a wide variety.
The authors found one category in particular: a group of bacteria called Chloroflexi. They seem to play a central role in the formation of this type of ecosystem. Like a kind of keystone. Because if Chloroflexi are not the most abundant bacteria found in this work, they are the only ones to be systematically present in each sample, for all sites.
« This study shows that it is possible that the oldest lineages of bacteria, such as the phylum Chloroflexi, could have an important ecological role. “, specifies the main author of the work, Rebecca D. Prescott, in a post July 21, 2022.
For years, biologists have discovered several determining “jobs” held by Chloroflexi within very different ecosystems. But this group of bacteria is extremely varied and very little studied. Reason why the Chloroflexi are nicknamed ” microbial dark matter ». The black matter seems to structure the cosmos without being observed or well understood, and biologists perceive the Chloroflexi in the same way: they structure a number of micro-organic ecosystems, while remaining very enigmatic to this day.
Community living in an extreme environment
The diversity of microbial species is greater than the authors anticipated, of course, but it remains lower than in less harsh environments. Except that the story brought to light by this study does not stop there. The interactions between these species paradoxically appear more complex in these extreme conditions. ” This begs a question, what if extreme environments help create more interactive microbial communities, with microorganisms more dependent on each other? And if so, how do extreme environments help create this? asks Rebecca D. Prescott.
By asking these questions, the study comes to shake the chips of scientific research to better interfere in the secrets of living things: it is crucial to study bacteria in “coculture”, by observing them evolving together, not by studying them each in isolation.
« In the natural world, microbes do not grow in isolation. Instead, they grow, live, and interact with many other microorganisms in a sea of chemical signals from all those other microbes. It can alter the expression of their genes, affect their roles in the community » insists Rebecca D. Prescott.
These reflections are all the more relevant in the light of exobiology, particularly Martian. These lava tubes and thermal chimneys resemble what may have existed on Mars in the old days. If you understand how these microbes behave, you can understand the history of the planet. But this obviously goes beyond the simple Martian framework, as it can also teach us about the history of the Earth… and bring its grain of salt for our future, microbes playing an important role in certain renewable natural resources.
