Scientists recently discovered a remarkable assortment of novel microbes on the island of Hawai'i, flourishing in geothermal caves, lava tubes, and volcanic vents.

ScienceAlert describes microbes as the tiniest "known living organisms on Earth" and can be located "just about everywhere, even in lava caves' cold Mars-like conditions.

Such underground structures were formed between 65 and 800 years ago and received little to no sunlight at all.

The said microbes are also harboring "toxic materials and gases." Nonetheless, bacterial mats are a common feature of Hawai'ian lava caves.

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Hawai'ian Lava Cave
(Photo: Wikimedia Commons/Dave Bunnell)
Thurston lava tube in Hawai'i Volcanoes National Park is the only one in the park open for visitors and is one of the most popular attractions.


Underexplored Diverse Ecosystems

Specimens of such mats, collected between 2006 and 2009 and then between 2017 and 2019, show even more unique forms than anticipated.

When the study authors sequenced 70 samples for a single RNA gene, typically used for determining microbial diversity and abundance, they could not match any outcomes to identified genera or species, at least not with great confidence.

The researchers then wrote in their research published in the Frontiers in Microbiology journal that their finding suggests that caves and fumaroles are "underexplored diverse ecosystems."

Next to plants, microbes account for the majority of the biomass of Earth and almost all the biomass in the deep subsurface of this planet.

Nevertheless, since these microbes are very small and live in very extreme environments, researchers have historically overlooked them.

In previous years, underground bacteria have received more interest due to their existence in environments very similar to those on Mars. There's still a long way to go, though.

Possibly a 'Dark Matter'

Recent approximations have suggested that 99.99 percent of all bacterium species stay unknown, leading some people to refer to them as "dark matter," a related Gizmodo report said.

The new study from Hawai'i highlights how obscure such life forms are. Diversity among the areas differed. Older lava tubes, those aged from 500 to 800 years old, hosted more diverse microbe populations than geothermically active areas or were below 400 years of age.

While the older sites were more diverse, the younger, not to mention more active sample areas had more complex bacterium interactions, possibly because of the lower diversity. Such bacteria may need to work together to survive better.

Researchers have suspected it takes time for bacteria to colonize volcanic basalts. More so, as the environment around them changes, so does their community structure.

Proteobacteria and Antinobacteria

In cooler caves, for example, proteobacteria and actinobacteria are more prevalent, leading microbiologist Rebecca Prescott from the University of Hawai'i at Manoa to wonder if extreme environments are helping in the creation of more interactive bacterial communities, with microorganisms more reliant on each other. If so, she added, "what is it about extreme environment" that's helping create this?

In younger lava caves, bacteria tended to be more distantly associated. This suggests that competition is more robust in harsher environments, lowering the chance of closely linked species living side by side.

Several classes of bacteria, such as Acidobacteria and Chloroflexi, existed at almost all sites, regardless of how old they were.

Such microbes appear to be key players in their communities. The researchers identify them as "hub" species as they bring other microbes together.

A report about the Hawai'ian lava cave is shown on Aflamnet Channel's YouTube video below:

 

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