Deep underground, scientists find thriving microbial ecosystems that defy explanation
Researchers discovered diverse microbial communities living in deep subsurface aquifers on minimal energy, yet they mysteriously stopped growing even when fed nutrients. The finding could reshape understanding of how microbes survive in extreme environments—with implications for geothermal energy, carbon storage, and predicting contamination in groundwater systems.
Originaltitel: Exploring microbial diversity using cell-size fractionated enrichment incubations from subsurface aquifers at Äspö, Sweden
<p>The continental subsurface hosts energy-constrained groundwaters with a high diversity of ecologically elusive microorganisms adapted to the prevailing low-energy conditions. This study explored potential interactions among microbes using anaerobic enrichment incubations with three types of groundwater of contrasting hydrochemistry from the & Auml;sp & ouml; Hard Rock Laboratory, Sweden. Removing cells larger than 0.45 & micro;m from the inoculum resulted in incubations enriched in populations characterized by very small genomes, including Patescibacteria, Nanobdellota, and Omnitrophota. These incubations had a higher diversity than non-fractionated incubations. However, cell numbers and community structure of the fractionated incubations did not change over an incubation period up to four months, despite high microbial diversity and experimental amendments with either simple (acetate) or more complex (cell lysate) carbon sources. In addition, network analysis on the groundwaters revealed multiple co-occurrences between populations affiliated with the Patescibacteria and the Desulfobacterota. Overall, these findings support that a considerable part of microbial diversity has a small cell size in these low energy groundwaters and strong co-occurrences among populations as an important survival strategy.</p>