Publications

4781

Summary Obligate acidophilic members of the thaumarchaeotal genus Candidatus Nitrosotalea play an important role in nitrification in acidic soils, but their evolutionary and physiological adaptations to acidic environments are still poorly understood, with only a single member of this genus ( Ca . N. devanaterra) having its genome sequenced. In this study, we sequenced the genomes of two additional cultured Ca . Nitrosotalea strains, extracted an almost complete Ca . Nitrosotalea metagenome‐assembled genome from an acidic fen, and performed comparative genomics of the four Ca . Nitrosotalea genomes with 19 other archaeal ammonia oxidiser genomes. Average nucleotide and amino acid identities revealed that the four Ca . Nitrosotalea strains represent separate species within the genus. The four Ca . Nitrosotalea genomes contained a core set of 103 orthologous gene families absent from all other ammonia‐oxidizing archaea and, for most of these gene families, expression could be demonstrated in laboratory culture or the environment via proteomic or metatranscriptomic analyses respectively. Phylogenetic analyses indicated that four of these core gene families were acquired by the Ca . Nitrosotalea common ancestor via horizontal gene transfer from acidophilic representatives of Euryarchaeota. We hypothesize that gene exchange with these acidophiles contributed to the competitive success of the Ca . Nitrosotalea lineage in acidic environments.

ABSTRACT We report the 4.55-Mbp genome of “ Candidatus Fluviicola riflensis” ( Bacteroidetes ) that was manually curated to completion from Illumina data. “ Ca . Fluviicola riflensis” is a facultative anaerobe. Its ability to grow over a range of O 2 levels may favor its proliferation in an aquifer adjacent to the Colorado River in the United States.

ABSTRACT The high-quality draft genome of “ Candidatus Methanoperedens sp.” strain BLZ2, a nitrate-reducing archaeon anaerobically oxidizing methane, is presented. The genome was obtained from an enrichment culture and measures 3.74 Mb. It harbors two nitrate reductase gene clusters, an ammonium-forming nitrite reductase, and the complete reverse methanogenesis pathway. Methane that escapes to the atmosphere acts as a potent greenhouse gas. Global methane emissions are mitigated by methanotrophs, which oxidize methane to CO 2 . “ Candidatus Methanoperedens spp.” are unique methanotrophic archaea that can perform nitrate-dependent anaerobic oxidation of methane. A high-quality draft genome sequence of only 85 contigs from this archaeon is presented here.

AbstractCultivation of microbial consortia provides low-complexity communities that can serve as tractable models to understand community dynamics. Time-resolved metagenomics demonstrated that an aerobic cellulolytic consortium cultivated from compost exhibited community dynamics consistent with the definition of an endogenous heterotrophic succession. The genome of the proposed pioneer population, ‘Candidatus Reconcilibacillus cellulovorans’, possessed a gene cluster containing multidomain glycoside hydrolases (GHs). Purification of the soluble cellulase activity from a 300litre cultivation of this consortium revealed that ~70% of the activity arose from the ‘Ca. Reconcilibacillus cellulovorans’ multidomain GHs assembled into cellulase complexes through glycosylation. These remarkably stable complexes have supramolecular structures for enzymatic cellulose hydrolysis that are distinct from cellulosomes. The persistence of these complexes during cultivation indicates that they may be active through multiple cultivations of this consortium and act as public goods that sustain the community. The provision of extracellular GHs as public goods may influence microbial community dynamics in native biomass-deconstructing communities relevant to agriculture, human health and biotechnology.