Abstract
We investigated the global patterns of abundance, diversity, and community structure of members of the Aminicenantes (candidate phylum OP8). Our aim was to identify the putative ecological role(s) played by members of this poorly characterized bacterial lineages in various ecosystems. Analysis of near full-length 16S rRNA genes identified four classes and eight orders within the Aminicenantes. Within 3,134 datasets comprising ∼1.8 billion high throughput-generated partial 16S rRNA genes, 47,351 Aminicenantes-affiliated sequences were identified in 913 datasets. The Aminicenantes exhibited the highest relative abundance in hydrocarbon-impacted environments, followed by marine habitats (especially hydrothermal vents and coral-associated microbiome samples), and aquatic, non-marine habitats (especially in terrestrial springs and groundwater samples). While the overall abundance of the Aminicenantes was higher in low oxygen tension as well as non-saline and low salinity habitats, it was encountered in a wide range of oxygen tension, salinities, and temperatures. Analysis of the community structure of the Aminicenantes showed distinct patterns across various datasets that appear to be, mostly, driven by habitat variations rather than prevalent environmental parameters. We argue that the detection of the Aminicenantes across environmental extremes and the observed distinct community structure patterns reflect a high level of intraphylum metabolic diversity and adaptive capabilities that enable its survival and growth in a wide range of habitats and environmental conditions.
Highlights
During the last quarter century, culture-independent diversity surveys have been extensively utilized to investigate bacterial diversity in almost all accessible habitats on earth [1,2,3,4,5]. These surveys have collectively demonstrated that the scope of bacterial diversity is much broader than previously expected based on culture-based assessments [6,7], with a large fraction of the 16S rRNA gene sequences encountered not belonging to known cultured bacterial phyla
Classes OP8-2, OP8-3, and OP8unclassified have a lower number of near full-length sequences and are not further sub-classified into candidate orders. This revision of Aminicenantes phylogeny increased the number of recognized near full-length 16S rRNA gene sequences by 30.3%, and added one candidate class (OP8-3) and one candidate order (OP81_YNP) to the Greengenes taxonomic outline, the most detailed Aminicenantes classification scheme in curated databases
We studied the effect of environmental conditions (O2 tension, temperature, and salinity) on Aminicenantes community structure in various datasets
Summary
During the last quarter century, culture-independent diversity surveys have been extensively utilized to investigate bacterial diversity in almost all accessible habitats on earth [1,2,3,4,5]. These include construction and screening of large insert (Fosmid and BAC) libraries [8,9,10,11], direct metagenomic surveys and subsequent implementation of novel binning approaches to reconstruct genomes from metagenomic sequence data [12,13,14,15], and single cell genomics [16,17,18,19] These efforts have yielded valuable insight regarding the genomic characteristics and putative metabolic capabilities of multiple novel candidate phyla. In several incidents, these insights were successfully utilized as a stepping-stone for enrichment and isolation of some of these lineages [20,21,22]
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