Microbial Diversity and Function in Shallow Subsurface Sediment and Oceanic Lithosphere of the Atlantis Massif

Abstract

The subsurface rock beneath the ocean is one of the largest biospheres on Earth, and microorganisms within influence global-scale nutrient cycles. This biosphere is difficult to study, in part due to the low concentrations of microorganisms that inhabit the vast volume of the marine lithosphere.

Expedition 399 Scientific Prospectus: Building Blocks of Life, Atlantis Massif

“…Distinguishing endemic microbial taxa from those introduced from seawater or contamination is a major challenge requiring multiple strategies to overcome (Kallmeyer et al, 2017;Sylvan et al, 2021;Pendleton et al, 2021). Nonetheless, the signatures of endolithic commu- nities have been successfully identified from the subseafloor of the Atlantis Massif during both Expeditions 304 (Mason et al, 2010) and 357 (Motamedi et al, 2020;Goordial et al, 2021;Quéméneur et al, 2019) (Figure F11). Despite the widespread dominance of communities that cycle H 2 and CH 4 in the Lost City hydrothermal chimneys (Schrenk et al, 2004(Schrenk et al, , 2013Brazelton et al, 2006), genes associated with H 2 and CH 4 metabolisms were rare or absent in the Atlantis Massif subseafloor (Goordial et al, 2021).…”

“…Nonetheless, the signatures of endolithic commu- nities have been successfully identified from the subseafloor of the Atlantis Massif during both Expeditions 304 (Mason et al, 2010) and 357 (Motamedi et al, 2020;Goordial et al, 2021;Quéméneur et al, 2019) (Figure F11). Despite the widespread dominance of communities that cycle H 2 and CH 4 in the Lost City hydrothermal chimneys (Schrenk et al, 2004(Schrenk et al, , 2013Brazelton et al, 2006), genes associated with H 2 and CH 4 metabolisms were rare or absent in the Atlantis Massif subseafloor (Goordial et al, 2021). In general, the genes necessary for autotrophic carbon fixation pathways were rare, whereas those associated with heterotrophy were regularly identified (Quéméneur et al, 2019;Motamedi et al, 2020;Goordial et al, 2021).…”

“…Despite the widespread dominance of communities that cycle H 2 and CH 4 in the Lost City hydrothermal chimneys (Schrenk et al, 2004(Schrenk et al, , 2013Brazelton et al, 2006), genes associated with H 2 and CH 4 metabolisms were rare or absent in the Atlantis Massif subseafloor (Goordial et al, 2021). In general, the genes necessary for autotrophic carbon fixation pathways were rare, whereas those associated with heterotrophy were regularly identified (Quéméneur et al, 2019;Motamedi et al, 2020;Goordial et al, 2021). Enrichment experiments also primarily identified microorganisms that rely on heterotrophy (Quéméneur et al, 2019).…”

“…Although early indications suggested that alkane degradation may be an important metabolic strategy in the gabbroic-dominated Hole U1309D (Mason et al, 2010), genes associated with alkane degradation were not detected in metagenomic studies of the more ultramafic Expedition 357 cores (Goordial et al, 2021). Using high-pressure incubations, a strictly anaerobic, mesophilic bacterium that relies on fermentation of organic compounds for growth was successfully isolated from Expedition 357 Hole M0070C (Quéméneur et al, 2019).…”

Cryomicrobial Ecology: Still Much To Learn about Life Left Out in the Cold

“…Our current work now investigates whether such cold-active microorganisms may be persisting in such environments cryptically, with metabolic rates too low and metabolism too slow to detect using standard microbiological approaches. To do this, our current work takes advantage of single-cell microbiology flow cytometry sorting techniques that can sequence the genomes of individual cells, even in low-biomass environments ( 18 , 19 ). When combined with fluorescent tagging techniques for active and replicating cells ( 20 ), cell sorting permits analysis of the genomics and activity of cryophilic microbes without requiring a cultivated isolate.…”