Marine ultra-small prokaryotes likely affect the cycling of Carbon, Methane, Nitrogen and Sulfur.

ABSTRACT: Recently, we uncovered the genetic components from six carbon fixation autotrophic pathways in cleaned ultra-small size fractions from marine samples (<0.22 micrometres) gathered worldwide by the Tara Oceans Expedition. This first finding suggested that prokaryotic nanoorganisms, phylogenetically distantly related to the known CPR and DPANN groups, could collectively impact carbon cycling and carbon fixation across the world's ocean. To extend our mining of the functional and taxonomic microbial dark matter from the ultra-small size fraction from the Tara Oceans Expedition, we investigated the distribution of 28 metabolic pathways associated with the cycling of carbon, methane, nitrogen and sulfur. For all of these pathways, we report the existence of novel metabolic homologs in the ultra-small size fraction of the oceanic microbiome, associated with nanoorganisms belonging to the CPR and DPANN lineages, but also of metabolic homologs exclusively found in marine host taxa belonging to other (still unassigned) microbial lineages. Therefore, we conclude that marine nanoorganisms contribute to a greater diversity of key biogeochemical cycles than currently appreciated. In particular, we suggest that oceanic nanoorganisms may be involved in a metabolic loop around Acetyl-CoA, have an underappreciated genetic potential to degrade methane, contribute to sustaining redox-reactions by producing Coenzyme F420, and affect sulfur cycling, notably as they harbour a complete suite of homologs of enzymes of the SOX system.

SUBMITTER: Lannes R 

PROVIDER: S-EPMC7851587 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature