Characterization ofMelioribacter roseusgen. nov., sp. nov., a novel facultatively anaerobic thermophilic cellulolytic bacterium from the classIgnavibacteria, and a proposal of a novel bacterial phylumIgnavibacteriae

Abstract

A novel moderately thermophilic, facultatively anaerobic chemoorganotrophic bacterium strain P3M-2(T) was isolated from a microbial mat developing on the wooden surface of a chute under the flow of hot water (46°C) coming out of a 2775-m-deep oil exploration well (Tomsk region, Russia). Strain P3M-2(T) is a moderate thermophile and facultative anaerobe growing on mono-, di- or polysaccharides by aerobic respiration, fermentation or by reducing diverse electron acceptors [nitrite, Fe(III), As(V)]. Its closest cultivated relative (90.8% rRNA gene sequence identity) is Ignavibacterium album, the only chemoorganotrophic member of the phylum Chlorobi. New genus and species Melioribacter roseus are proposed for isolate P3M-2(T) . Together with I. album, the new organism represents the class Ignavibacteria assigned to the phylum Chlorobi. The revealed group includes a variety of uncultured environmental clones, the 16S rRNA gene sequences of some of which have been previously attributed to the candidate division ZB1. Phylogenetic analysis of M. roseus and I. album based on their 23S rRNA and RecA sequences confirmed that these two organisms could represent an even deeper, phylum-level lineage. Hence, we propose a new phylum Ignavibacteriae within the Bacteroidetes-Chlorobi group with a sole class Ignavibacteria, two families Ignavibacteriaceae and Melioribacteraceae and two species I. album and M. roseus. This proposal correlates with chemotaxonomic data and phenotypic differences of both organisms from other cultured representatives of Chlorobi. The most essential differences, supported by the analyses of complete genomes of both organisms, are motility, facultatively anaerobic and obligately organotrophic mode of life, the absence of chlorosomes and the apparent inability to grow phototrophically.

Hot Spring Microbial Community Composition, Morphology, and Carbon Fixation: Implications for Interpreting the Ancient Rock Record

“…The Ignavibacteria OTUs were most closely related to Ignavibacteriales assigned to the Families SR-FBR-L83 and IheB3-7. Neither have cultured representatives but a close relative of SR-FBR-L83 is a moderate thermophile and facultative anaerobe that can respire diverse electron acceptors, e.g., Fe(III), NO (Podosokorskaya et al, 2013). OTUs affiliated with Deinococci (Thermus and Meiothermus FIGURE 3 | Composition of small subunit rRNA gene sequences for (A) bacteria, (B) archaea, and (C) eukarya from microbial samples equivalent to those used for carbon uptake experiments at Sites 1, 2, 3, and 4.…”

Presence and Role of Anaerobic Hydrolytic Microbes in Conversion of Lignocellulosic Biomass for Biogas Production

“…This microorganism is able to grow on avicel and xylan. Genome analyses of Chlorobi confirmed the presence of genes coding for hydrolytic enzymes (Podosokorskaya et al, 2013;Kadnikov et al, 2013). In biogas plants, members of the Chlorobi were less frequently detected (Kampmann et al, 2012;Li et al, 2013).…”

Implications of Limited Thermophilicity of Nitrite Reduction for Control of Sulfide Production in Oil Reservoirs

“…At 60°C, in addition to Geobacillus, Ignavibacteria were a major community component. Cultured representatives of this class are thermophilic, facultatively anaerobic heterotrophs found in oil fields (35).…”