Tremendous Diversity and Connectedness in Microorganism Communities in the High-Temperature Deep Sea – ScienceDaily

A new study by researchers at Portland State University and the University of Wisconsin finds that a rich diversity of microorganisms live in close-knit communities in superheated geothermal environments in the deep sea. The study published in the journal microbiome, led by Anna Louise Reisenbach, Professor of Biology at Prince Sultan University. Emily St. John, who has a master’s degree in microbial ecology from Prince Sultan bin Abdulaziz University, contributed significantly to the study, along with researchers from the University of Wisconsin.

When the 350-400 °C liquid that emerges from the Earth’s crust through deep-sea hydrothermal vents mixes with sea water, it produces large porous rocks that are often referred to as “stacks” or hydrothermal deposits. These stacks are colonized by microbes that thrive in high-temperature environments. For decades, Reysenbach has collected chimneys from deep-sea hydrothermal vents across the world’s oceans, and her lab is using genetic fingerprinting and farming techniques to study the microbial diversity of the communities associated with these rocks.

In this new study, Reysenbach and the team were able to take advantage of advances in molecular biology techniques to sequence the whole genome of microbes in these communities to learn more about their diversity and interconnected ecosystems.

The team built the genomes of 3,635 bacteria and archaea from 40 different rock communities. The amount of diversity was amazing and greatly expands what is known about how many different species of bacteria and archaea existed. Researchers have discovered at least 500 new genera (the level of taxonomic organization above species) and have evidence of two new groups (five levels above species). “Phyla is pretty high up in the rankings, so that’s really cool,” says Reysenbach.

The team also found evidence of hotspots of microbial diversity. Samples from a deep-sea volcano near New Zealand, for example, have been enriched with various types of microorganisms, many of which are endemic to the volcano.

“This biodiversity was just huge, off the charts,” says Reysenbach. “In one volcano there was a lot of new diversity that we hadn’t seen elsewhere before.” This result may indicate that the increased complexity of the volcano’s subsurface rocks makes them more likely to harbor diverse microbial species compared to deep-sea hydrothermal vents.

Besides finding a surprising amount of microorganism biodiversity in these high-temperature ecosystems, the genomic data from this study also showed that many of these organisms depend on each other to survive. By analyzing the genome, the researchers found that some microorganisms cannot metabolize all the nutrients they need to survive, so they depend on nutrients produced by other species in a process known as “metabolic handover.”

“By looking at these genomes, we really got a much better understanding of what a lot of these microorganisms do and how they interact,” says Reysenbach. “They are communal; they share food with each other.”

This study inspired a new phase of Reysenbach’s research: gaining an in-depth understanding of the interactions between these microorganisms in the deep sea. “The most exciting part for me is that I really want to be able to grow these things in the lab,” says Reysenbach. “I want to be able to see [a microorganism] under a microscope and understand if he needs someone else to live with.”

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