AUTHOR=Vigneron Adrien , Cruaud Perrine , Guyoneaud Rémy , Goñi-Urriza Marisol 

TITLE=Into the darkness of the microbial dark matter in situ activities through expression profiles of Patescibacteria populations

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.1073483

DOI=10.3389/fmicb.2022.1073483

ISSN=1664-302X

ABSTRACT=<p><italic>Patescibacteria</italic> form a highly diverse and widespread superphylum of uncultured microorganisms representing a third of the global microbial diversity. Most of our knowledge on <italic>Patescibacteria</italic> putative physiology relies on metagenomic mining and metagenome-assembled genomes, but the <italic>in situ</italic> activities and the ecophysiology of these microorganisms have been rarely explored, leaving the role of <italic>Patescibacteria</italic> in ecosystems elusive. Using a genome-centric metatranscriptomic approach, we analyzed the diel and seasonal gene transcription profiles of 18 <italic>Patescibacteria</italic> populations in brackish microbial mats to test whether our understanding of <italic>Patescibacteria</italic> metabolism allows the extrapolation of their <italic>in situ</italic> activities. Although our results revealed a circadian cycle in <italic>Patescibacteria</italic> activities, a strong streamlined genetic expression characterized the <italic>Patescibacteria</italic> populations. This result has a major consequence for the extrapolation of their physiology and environmental function since most transcribed genes were uncharacterized, indicating that the ecophysiology of <italic>Patescibacteria</italic> cannot be yet reliably predicted from genomic data.</p>