Lava caves in Hawaii are teeming with bacterial ‘dark matter’

The volcanic environment of Hawaii contains a new study this week found a rich array of mysterious microbes. Scientists say that lava caves and other structures created by volcanic activity are home to unique, diverse and hitherto unexplored communities of bacteria. The findings show that there is still much to be learned about life in some of the most extreme environments on Earth.

Researchers from several universities and NASA collaborated on a study that was published Thursday at Frontiers in Microbiology. They studied samples collected from 70 locations along the Great Hawaiian Island, the largest island in the Hawaiian archipelago. These places included caves, pipes and fumaroles, which are openings or vents through which volcanic gases and water can escape. They analyzed and sequenced the RNA found in the samples, which made it possible to create a rough map of the bacterial communities living there.

Some of these areas, especially those where geothermal activity continues, are some of the most inhospitable places in the world as they are incredibly hot and filled with chemicals that are toxic to most living things. Thus, the research team expected to find relatively little diversity of life in sites with such extreme conditions. The researchers found that older caves and pipes that formed more than 500 years ago had a greater bacterial diversity. But, to their surprise, even active geothermal springs were filled with a wide variety of bacteria. And compared to other places, the bacterial communities in these harsher habitats also appeared to be more complex in how they interacted with one another.

“This leads to the question, does extreme conditions help create more interactive microbial communities in which microorganisms are more dependent on each other?” said study author Rebecca Prescott, a researcher at NASA’s Johnson Space Center and the University of Hawaii. statement. “And if so, what is it about extreme conditions that helps create it?

Bacteria found in these locations also rarely crossed, meaning that these environments appear to contain their own unique microbial worlds, and at least thousands of unknown species have yet to be identified. One group of bacteria in particular, known as Chloroflexi, may be particularly influential as they are commonly found in various volcanic areas and appear to interact with many other organisms. And it is possible that they may be an example of “central species” – microbes vital to the structure and functioning of their communities.

“This study points to the possibility that older lines of bacteria, such as the Chloroflexi phylum, may have important ecological ‘jobs’ or roles,” Prescott said. “Chloroflexi is an extremely diverse group of bacteria with many different functions in a wide variety of environments, but they are not well understood so we don’t know what they do in these communities. Some scientists call such groups “microbial dark matter” – invisible or unexplored microorganisms in nature.

These sorts of genetic sampling studies can provide a broad picture of the bacterial world found in a particular location, but no more detailed information about individual species or the role they play in their tiny neighbors. Therefore, scientists say more research is needed to unravel the mystery of these volcanic inhabitants. Over time, what we learn could be relevant to our understanding of how life began on Earth or even Mars, as these environments could be the closest existing analog of what the planets looked like a long time ago.