Publications

4634

SignificanceDiverse microbial life has been detected in the cold desert soils of Antarctica once thought to be barren. Here, we provide metagenomic, biogeochemical, and culture-based evidence that Antarctic soil microorganisms are phylogenetically and functionally distinct from those in other soils and adopt various metabolic and ecological strategies. The most abundant community members are metabolically versatile aerobes that use ubiquitous atmospheric trace gases to potentially meet energy, carbon, and, through metabolic water production, hydration needs. Lineages capable of harvesting solar energy, oxidizing edaphic inorganic substrates, or adopting symbiotic lifestyles were also identified. Altogether, these findings provide insights into microbial adaptation to extreme water and energy limitation and will inform ongoing efforts to conserve the unique biodiversity on this continent.

Here, we report the draft, nearly complete genome sequence of the human oral actinobacterium Schaalia odontolytica strain ORNL0103, which was isolated in association with “ Candidatus Saccharibacteria” HMT352 strain ORNL0105. The genome was sequenced using a combination of Pacific Biosciences and Illumina platforms and encodes 1,948 proteins and 60 RNAs.

Abstract Members of the genus Acidithiobacillus, now ranked within the class Acidithiobacillia, are model bacteria for the study of chemolithotrophic energy conversion under extreme conditions. Knowledge of the genomic and taxonomic diversity of Acidithiobacillia is still limited. Here, we present a systematic analysis of nearly 100 genomes from the class sampled from a wide range of habitats. Some of these genomes are new and others have been reclassified on the basis of advanced genomic analysis, thus defining 19 Acidithiobacillia lineages ranking at different taxonomic levels. This work provides the most comprehensive classification and pangenomic analysis of this deep-branching class of Proteobacteria to date. The phylogenomic framework obtained illuminates not only the evolutionary past of this lineage, but also the molecular evolution of relevant aerobic respiratory proteins, namely the cytochrome bo3 ubiquinol oxidases.

Abstract Acidobacteriota are widespread and often abundant in marine sediments, yet their metabolic and ecological properties are poorly understood. Here, we examined metabolisms and distributions of Acidobacteriota in marine sediments of Svalbard by functional predictions from metagenome-assembled genomes (MAGs), amplicon sequencing of 16S rRNA and dissimilatory sulfite reductase (dsrB) genes and transcripts, and gene expression analyses of tetrathionate-amended microcosms. Acidobacteriota were the second most abundant dsrB-harboring (averaging 13%) phylum after Desulfobacterota in Svalbard sediments, and represented 4% of dsrB transcripts on average. Meta-analysis of dsrAB datasets also showed Acidobacteriota dsrAB sequences are prominent in marine sediments worldwide, averaging 15% of all sequences analysed, and represent most of the previously unclassified dsrAB in marine sediments. We propose two new Acidobacteriota genera, Candidatus Sulfomarinibacter (class Thermoanaerobaculia, “subdivision 23”) and Ca. Polarisedimenticola (“subdivision 22”), with distinct genetic properties that may explain their distributions in biogeochemically distinct sediments. Ca. Sulfomarinibacter encode flexible respiratory routes, with potential for oxygen, nitrous oxide, metal-oxide, tetrathionate, sulfur and sulfite/sulfate respiration, and possibly sulfur disproportionation. Potential nutrients and energy include cellulose, proteins, cyanophycin, hydrogen, and acetate. A Ca. Polarisedimenticola MAG encodes various enzymes to degrade proteins, and to reduce oxygen, nitrate, sulfur/polysulfide and metal-oxides. 16S rRNA gene and transcript profiling of Svalbard sediments showed Ca. Sulfomarinibacter members were relatively abundant and transcriptionally active in sulfidic fjord sediments, while Ca. Polarisedimenticola members were more relatively abundant in metal-rich fjord sediments. Overall, we reveal various physiological features of uncultured marine Acidobacteriota that indicate fundamental roles in seafloor biogeochemical cycling.