Dataset Information

Unusual respiratory capacity and nitrogen metabolism in a Parcubacterium (OD1) of the Candidate Phyla Radiation.

ABSTRACT: The Candidate Phyla Radiation (CPR) is a large group of bacteria, the scale of which approaches that of all other bacteria. CPR organisms are inferred to depend on other community members for many basic cellular building blocks and all appear to be obligate anaerobes. To date, there has been no evidence for any significant respiratory capacity in an organism from this radiation. Here we report a curated draft genome for 'Candidatus Parcunitrobacter nitroensis' a member of the Parcubacteria (OD1) superphylum of the CPR. The genome encodes versatile energy pathways, including fermentative and respiratory capacities, nitrogen and fatty acid metabolism, as well as the first complete electron transport chain described for a member of the CPR. The sequences of all of these enzymes are highly divergent from sequences found in other organisms, suggesting that these capacities were not recently acquired from non-CPR organisms. Although the wide respiration-based repertoire points to a different lifestyle compared to other CPR bacteria, we predict similar obligate dependence on other organisms or the microbial community. The results substantially expand the known metabolic potential of CPR bacteria, although sequence comparisons indicate that these capacities are very rare in members of this radiation.

SUBMITTER: Castelle CJ

PROVIDER: S-EPMC5220378 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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Unusual respiratory capacity and nitrogen metabolism in a Parcubacterium (OD1) of the Candidate Phyla Radiation.

Castelle Cindy J CJ Brown Christopher T CT Thomas Brian C BC Williams Kenneth H KH Banfield Jillian F JF

Scientific reports 20170109

The Candidate Phyla Radiation (CPR) is a large group of bacteria, the scale of which approaches that of all other bacteria. CPR organisms are inferred to depend on other community members for many basic cellular building blocks and all appear to be obligate anaerobes. To date, there has been no evidence for any significant respiratory capacity in an organism from this radiation. Here we report a curated draft genome for 'Candidatus Parcunitrobacter nitroensis' a member of the Parcubacteria (OD1) ...[more]

PMID: 28067254

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Project description:The Candidate Phyla Radiation (CPR) is a recently described expansion of the tree of life that represents more than 15% of all bacterial diversity and potentially contains over 70 different phyla. Despite this broad phylogenetic variation, these microorganisms appear to feature little functional diversity, with members generally characterized as obligate fermenters. Additionally, much of the data describing CPR phyla has been generated from a limited number of environments, constraining our knowledge of their functional roles and biogeographical distribution. To expand our understanding of subsurface CPR microorganisms, we sampled four separate groundwater wells over 2 years across three Ohio counties.Samples were analyzed using 16S rRNA gene amplicon and shotgun metagenomic sequencing. Amplicon results indicated that CPR members comprised between 2 and 20% of the microbial communities with relative abundances stable through time in Athens and Greene samples but dynamic in Licking groundwater. Shotgun metagenomic analyses generated 71 putative CPR genomes, representing roughly 32 known phyla and 2 putative new phyla, Candidatus Brownbacteria and Candidatus Hugbacteria. While these genomes largely mirrored metabolic characteristics of known CPR members, some features were previously uncharacterized. For instance, nitrite reductase, encoded by nirK, was found in four of our Parcubacteria genomes and multiple CPR genomes from other studies, indicating a potentially undescribed role for these microorganisms in denitrification. Additionally, glycoside hydrolase (GH) family profiles for our 71 genomes and over 2000 other CPR genomes were analyzed to characterize their carbon-processing potential. Although common trends were present throughout the radiation, differences highlighted potential mechanisms that could allow microorganisms across the CPR to occupy various subsurface niches. For example, members of the Microgenomates superphylum appear to potentially degrade a wider range of carbon substrates than other CPR phyla.CPR members are present across a range of environments and often constitute a significant fraction of the microbial population in groundwater systems, particularly. Further sampling of such environments will resolve this portion of the tree of life at finer taxonomic levels, which is essential to solidify functional differences between members that populate this phylogenetically broad region of the tree of life.

Project description:Candidate Phyla Radiation (CPR) bacteria and nanoarchaea populate most ecosystems but are rarely detected in soil. We concentrated particles of less than 0.2 μm in size from grassland soil, enabling targeted metagenomic analysis of these organisms, which are almost totally unexplored in largely oxic environments such as soil. We recovered a diversity of CPR bacterial and some archaeal sequences but no sequences from other cellular organisms. The sampled sequences include Doudnabacteria (SM2F11) and Pacearchaeota, organisms rarely reported in soil, as well as Saccharibacteria, Parcubacteria, and Microgenomates. CPR and archaea of the phyla Diapherotrites, Parvarchaeota, Aenigmarchaeota, Nanoarchaeota, and Nanohaloarchaeota (DPANN) were enriched 100- to 1,000-fold compared to that in bulk soil, in which we estimate each of these organisms comprises approximately 1 to 100 cells per gram of soil. Like most CPR and DPANN sequenced to date, we predict these microorganisms live symbiotic anaerobic lifestyles. However, Saccharibacteria, Parcubacteria, and Doudnabacteria genomes sampled here also harbor ubiquinol oxidase operons that may have been acquired from other bacteria, likely during adaptation to aerobic soil environments. We conclude that CPR bacteria and DPANN archaea are part of the rare soil biosphere and harbor unique metabolic platforms that potentially evolved to live symbiotically under relatively oxic conditions. IMPORTANCE Here, we investigated overlooked microbes in soil, Candidate Phyla Radiation (CPR) bacteria and Diapherotrites, Parvarchaeota, Aenigmarchaeota, Nanoarchaeota, and Nanohaloarchaeota (DPANN) archaea, by size fractionating small particles from soil, an approach typically used for the recovery of viral metagenomes. Concentration of these small cells (<0.2 μm) allowed us to identify these organisms as part of the rare soil biosphere and to sample genomes that were absent from non-size-fractionated metagenomes. We found that some of these predicted symbionts, which have been largely studied in anaerobic systems, have acquired aerobic capacity via lateral transfer that may enable adaptation to oxic soil environments. We estimate that there are approximately 1 to 100 cells of each of these lineages per gram of soil, highlighting that the approach provides a window into the rare soil biosphere and its associated genetic potential.

Project description:Microbes belonging to Candidate Phyla Radiation (CPR) have joined the tree of life as a new branch, thanks to the intensive application of metagenomics and sequencing technologies. CPR have been eventually identified by 16S rRNA analysis, and they represent more than 26% of microbial diversity. Despite their ultrasmall size, reduced genome, and metabolic pathways which mainly depend on exosymbiotic or exoparasitic relationships with the bacterial host, CPR microbes were found to be abundant in almost all environments. They can be considered survivors in highly competitive circumstances within microbial communities. However, their defense mechanisms and phenotypic characteristic remain poorly explored. Here, we conducted a thorough in silico analysis on 4,062 CPR genomes to search for antibiotic resistance (AR)-like enzymes using BLASTp and functional domain predictions against an exhaustive consensus AR database and conserved domain database (CDD), respectively. Our findings showed that a rich reservoir of divergent AR-like genes (n = 30,545 hits, mean = 7.5 hits/genome [0 to 41]) were distributed across the 13 CPR superphyla. These AR-like genes encode 89 different enzymes that are associated with 14 different chemical classes of antimicrobials. Most hits found (93.6%) were linked to glycopeptide, beta-lactam, macrolide-lincosamide-streptogramin (MLS), tetracycline, and aminoglycoside resistance. Moreover, two AR profiles were discerned for the Microgenomates group and "Candidatus Parcubacteria," which were distinct between them and differed from all other CPR superphyla. CPR cells seem to be active players during microbial competitive interactions; they are well equipped for microbial combat in different habitats, which ensures their natural survival and continued existence. IMPORTANCE To our knowledge, this study is one of the few studies that characterize the defense systems in the CPR group and describes the first repertoire of antibiotic resistance (AR) genes. The use of a BLAST approach with lenient criteria followed by a careful examination of the functional domains has yielded a variety of enzymes that mainly give three different mechanisms of action of resistance. Our genome analysis showed the existence of a rich reservoir of CPR resistome, which is associated with different antibiotic families. Moreover, this analysis revealed the hidden face of the reduced-genome CPR, particularly their weaponry with AR genes. These data suggest that CPR are competitive players in the microbial war, and they can be distinguished by specific AR profiles.

Dataset Information

Unusual respiratory capacity and nitrogen metabolism in a Parcubacterium (OD1) of the Candidate Phyla Radiation.

Publications

Unusual respiratory capacity and nitrogen metabolism in a Parcubacterium (OD1) of the Candidate Phyla Radiation.

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