Lava Caves in Hawaiian Islands Have Fascinating Collection of Novel Microbes

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Lava Caves
Courtesy of Jimmy Emerson, DVM (Flickr CC0)

Scientists recently discovered a fascinating collection of novel microbes living in lava tubes, geothermal caves, and volcanic vents in Hawaii. Microbes are tiny, ubiquitous life forms almost everywhere on Earth, including in cold, Mars-like lava caves.

These habitats, built 65 and 800 years ago, receive little to no sunlight. Toxic minerals and gases may also be present. Despite this, the Hawaiian lava caves are home to microbial mats.

Samples of these mats were collected between 2006 and 2009, followed by another set between 2017 and 2019. They discovered even more strange life forms than expected. None of the 70 RNA genes tested could be matched to any recognized genus or species, at least with high certainty.

According to the researchers, lava caves and fumaroles are under-explored diverse ecosystems. Despite being so tiny and living in such a hostile environment, scientists have historically ignored underground organisms.

Earth’s subsurface is home to nearly all of the planet’s living biomass, yet scientists have traditionally overlooked these organisms because they are so small and live in such harsh environments.

Studies have shown that lava caves’ underground life is becoming more critical in recent years because it exists in environments very similar to those found on Mars. However, there is still a long way to go.

Some scholars argue that 99.999 percent of all creature species remain hidden, so they dubbed them “dark matter.”

Lava Caves
Courtesy of Pedro Szekely (Flickr CC0)

The new Hawaiian lava caves research reveals just how elusive these life forms are.

The variety of microorganism populations at the sites was variable. Lava tubes between 500 and 800 years old were home to more varied microbial people than geothermically active sites or sites less than 400 years old.

The older sites contained a more comprehensive range of microbes. However, the more active and younger sample sites contained a more complicated microbial community, most likely due to lower microbial diversity. The microbes may need to cooperate to survive.

Researchers believe that Proteobacteria and Actinobacteria flourish in cooler lava caves because the environments change the microbes’ community structures.

In younger lava caves, distant species lived closer together, suggesting that competition is more potent in harsher environments, lowering the chance of kindred species living together.

Regardless of the site’s age, there were still three bacterial classes: Chloroflexi, Acidobacteria, and others. The authors say these microbes are essential in connecting with other microbes. They refer to them as “hub” species.

It is conceivable that Chloroflexi microbes might provide carbon sources in the ecosystem by using light energy in relatively dark conditions.
In the current study, Prescott and her colleagues only analyzed a single gene to figure out what sort of microbe lives underground. As a result, they can’t say what a particular microbe’s function is.

Prescott believes that individual microorganisms cannot co-exist due to their own gene expression. This experiment demonstrated the importance of co-cultures rather than personal isolation.

Written by Janet Grace Ortigas

Sources:

Science Alert: Ancient Lava Caves in Hawai’i Are Teeming With Mysterious Life Forms, by Carly Cassella
Science Slashdot: Ancient Lava Caves in Hawai’i Are Teeming With Mysterious Life Forms
New Zealand News: Ancient Lava Caves in Hawai’i Are Teeming With Mysterious Life Forms & More Nz Today News

Featured and Top Image Courtesy of Jimmy Emerson, DVM’s Flickr Page – Creative Commons License
Inset Image Courtesy of Pedro Szekely‘s Flickr Page – Creative Commons License

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