Mysterious life forms found in centuries-old Hawaiian lava caves

A stalactite formation in a Hawaiian cave system from this study with copper minerals and white microbial colonies. Although copper is toxic to many organisms, this formation harbors a microbial community. (Credit: Kenneth Ingham)

Hundreds of years ago, the volcanic processes that created the islands of Hawaii also formed a network of underground tunnels and caves.

They are cold, dark and filled with toxic gases and minerals. So pretty much inhospitable to most life forms.

However, scientists have discovered that these volcanic vents actually contain colonies of complex, sprawling microbes.

They are the smallest known living organisms on Earth and we really don’t know much about them.

In fact, estimates suggest that 99.999% of all species of microbes remain unknown. As a result, some call these mysterious life forms “dark matter.”

Yet they still make up a huge amount of the earth’s biomass.

Thick microbial mats hang below a rocky ledge in steam vents that run along the Eastern Rift Zone on the island of Hawaii.  Image credit: Jimmy Saw

Thick microbial mats hang below a rocky ledge in steam vents that run along the East Rift Zone on the island of Hawaii. Image (Credit: Jimmy Saw)

What interests experts so much in the lava caves of Hawaii is that the conditions there are as close as possible to those of Mars or other distant planets.

And if microbes can survive in these 600-800-year-old lava tubes, we might find them on Mars at some point.

The researchers found that older lava caves, dating back more than 500 years, generally contained a more diverse population of microbes.

Therefore, they think it takes a long time for these tiny little creatures to colonize the volcanic basalt. As the environment changes over the eternities, their social structure also changes.

When the caves are younger and even more active, their colonies of microbes approach each other in terms of species.

“This brings us to the next question: do extreme environments contribute to creating more interactive microbial communities, with microorganisms more dependent on each other?” said microbiologist Rebecca Prescott of the University of Hawaii at Mānoa.

“And if so, what is in the extreme environments that contributes to creating this?”

Green and purple biofilms and microbial mats are common in geothermally active sites on the island of Hawaii and often contain the cyanobacterium Gloeobacter kilaueensis, a unique group of cyanobacteria that do not harvest light using thylakoids;  instead, photosynthesis occurs inside the plasma membrane.  (Credit: Stuart Donachie)

Green and purple biofilms and microbial mats are common in geothermally active sites on the island of Hawaii. (Credit: Stuart Donachie)

Although there’s a lot we don’t know, scientists suspect that competition is a stronger force in tougher environments.

“Overall, this study helps illustrate how important it is to study microbes in co-culture, rather than growing them alone (as isolates),” Prescott added.

“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 those other microbes. This can then alter the expression of their genes, affecting their jobs in the community.

The results of the study have been published in the journal Frontiers in Microbiology.

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