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.

A novel obligately anaerobic, mesophilic, organotrophic bacterium, strain P3M-1T, was isolated from a microbial mat formed in a wooden bath filled with hot water emerging from a 2775 m-deep well in the Tomsk region of western Siberia, Russia. Cells of strain P3M-1T were rod-shaped, 0.3–0.7 µm in width and formed multicellullar filaments that reached up to 400 µm in length. Strain P3M-1T grew optimally at 42–45 °C, pH 7.5–8.0, and with 0.1% (w/v) NaCl. Under optimal conditions, the doubling time was 6 h. The isolate was able to ferment a variety of proteinaceous substrates and sugars, including microcrystalline cellulose. Acetate, ethanol and H2 were the main products of glucose fermentation. The genomic DNA G+C content was 55 mol%. 16S rRNA gene sequence-based phylogenetic analyses showed that strain P3M-1T was a member of the class Anaerolinea , with 92.8 % sequence similarity to Levilinea saccharolytica KIBI-1T. Based on phylogenetic analysis and physiological properties, strain P3M-1T represents a novel species in a new genus, for which the name Ornatilinea apprima gen. nov., sp. nov. is proposed; the type strain of O. apprima is P3M-1T ( = DSM 23815T = VKM B-2669T).

Melioribacter roseus is a moderately thermophilic facultatively anaerobic organotrophic bacterium representing a novel deep branch within Bacteriodetes/Chlorobi group. To better understand the metabolic capabilities and possible ecological functions of M. roseus and get insights into the evolutionary history of this bacterial lineage, we sequenced the genome of the type strain P3M-2T. A total of 2838 open reading frames was predicted from its 3.30 Mb genome. The whole proteome analysis supported phylum-level classification of M. roseus since most of the predicted proteins had closest matches in Bacteriodetes, Proteobacteria, Chlorobi, Firmicutes and deeply-branching bacterium Caldithrix abyssi, rather than in one particular phylum. Consistent with the ability of the bacterium to grow on complex carbohydrates, the genome analysis revealed more than one hundred glycoside hydrolases, glycoside transferases, polysaccharide lyases and carbohydrate esterases. The reconstructed central metabolism revealed pathways enabling the fermentation of complex organic substrates, as well as their complete oxidation through aerobic and anaerobic respiration. Genes encoding the photosynthetic and nitrogen-fixation machinery of green sulfur bacteria, as well as key enzymes of autotrophic carbon fixation pathways, were not identified. The M. roseus genome supports its affiliation to a novel phylum Ignavibateriae, representing the first step on the evolutionary pathway from heterotrophic ancestors of Bacteriodetes/Chlorobi group towards anaerobic photoautotrophic Chlorobi.

A novel strictly anaerobic, halotolerant, organotrophic bacterium, strain P3M-3 T , was isolated from a microbial mat formed under the flow of hot water emerging from a 2775 m-deep well in Tomsk region (western Siberia, Russia). Cells of strain P3M-3 T were straight and curved rods, 0.2-0.4 mm in width and 1.5-20 mm in length. Strain P3M-3 T grew optimally at 37 6C, pH 7.0-7.5 and in a NaCl concentration of 15 g l "1 . Under optimum growth conditions, the doubling time was 1 h. The isolate was able to ferment a variety of mono-, di-and polysaccharides, including microcrystalline cellulose. Acetate, ethanol, H 2 and CO 2 were the main products of glucose fermentation. The DNA G+C content was 33.4 mol%. 16S rRNA gene-based phylogenetic analysis showed that strain P3M-3 T was a member of family Lachnospiraceae, whose representatives are also found in Clostridium cluster XIVa. 16S rRNA gene sequence similarity with Clostridium jejuense HY-35-12 T , the closest relative, was 93.9 %. A novel genus and species, Mobilitalea sibirica gen. nov., sp. nov., are proposed based on phylogenetic analysis and physiological properties of the novel isolate. The type strain of the type species is P3M-3The order Clostridiales, characterized by its phenotypical, chemotaxonomical, physiological and ecological diversity (Rainey, 2009a), includes 13 families and more than 600 species with validly published names at the time of writing. A majority of these species, including members of the most numerous genus Clostridium, are characterized as obligately anaerobic, chemo-organotrophic, fermentative, sporeforming rods. Since Collins et al. (1994) demonstrated the extensive phylogenetic diversity of the species assigned to the genus Clostridium, among XIX clusters, members of cluster I, widely regarded as the Clostridium sensu stricto, and a number of species of other clusters have been reclassified to existing genera or to novel ones. Nevertheless, currently there is a significant number of species of the genus Clostridium which have not, as yet, been reassigned to new genera, and remain distributed throughout families of the order Clostridiales. Moreover, many species continue to be added to the genus Clostridium even though they are not members of cluster I, leading to taxonomic confusion associated with this taxon (Rainey et al., 2009).The family Lachnospiraceae of the order Clostridiales was described based on phylogenetic analyses of 16S rRNA gene sequences (Rainey, 2009b). At the time of writing, this family contains 41 species with validly published names in 24 genera. Among these are several species formally affiliated with Clostridium cluster XIVa (Collins et al., 1994), whose taxonomy needs to be verified. Members of the family Lachnospiraceae are morphologically diverse and include Gram-stain-variable rods, vibrions and cocci. Nevertheless, all members are Gram-positive by cell wall structure and share similar physiology. They are mesophilic, strictly anaerobic, catalase-negative, chemoorganotrophic bacteria, able to hydrolyse p...

The goal of this work was to study the diversity of microorganisms inhabiting a deep subsurface aquifer system in order to understand their functional roles and interspecies relations formed in the course of buried organic matter degradation. A microbial community of a deep subsurface thermal aquifer in the Tomsk Region, Western Siberia was monitored over the course of 5 years via a 2.7 km deep borehole 3P, drilled down to a Palaeozoic basement. The borehole water discharges with a temperature of ca. 50°C. Its chemical composition varies, but it steadily contains acetate, propionate, and traces of hydrocarbons and gives rise to microbial mats along the surface flow. Community analysis by PCR-DGGE 16S rRNA genes profiling, repeatedly performed within 5 years, revealed several dominating phylotypes consistently found in the borehole water, and highly variable diversity of prokaryotes, brought to the surface with the borehole outflow. The major planktonic components of the microbial community were Desulfovirgula thermocuniculi and Methanothermobacter spp. The composition of the minor part of the community was unstable, and molecular analysis did not reveal any regularity in its variations, except some predominance of uncultured Firmicutes. Batch cultures with complex organic substrates inoculated with water samples were set in order to enrich prokaryotes from the variable part of the community. PCR-DGGE analysis of these enrichments yielded uncultured Firmicutes, Chloroflexi, and Ignavibacteriae. A continuous-flow microaerophilic enrichment culture with a water sample amended with acetate contained Hydrogenophilus thermoluteolus, which was previously detected in the microbial mat developing at the outflow of the borehole. Cultivation results allowed us to assume that variable components of the 3P well community are hydrolytic organotrophs, degrading buried biopolymers, while the constant planktonic components of the community degrade dissolved fermentation products to methane and CO2, possibly via interspecies hydrogen transfer. Occasional washout of minor community components capable of oxygen respiration leads to the development of microbial mats at the outflow of the borehole where residual dissolved fermentation products are aerobically oxidized. Long-term community analysis with the combination of molecular and cultivation techniques allowed us to characterize stable and variable parts of the community and propose their environmental roles.

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A novel obligately anaerobic, extremely thermophilic, organotrophic bacterium, strain 1445t T , was isolated from a hot spring on Kunashir Island (Kuril Islands, Russia). Cells were motile rods (0.4-0.5¾1.0-3.0 mm). The temperature range for growth at pH 7.8 was 46-80 6C, with optimum growth at 65 6C. The pH range for growth at 65 6C was pH 5.7-9.0, with optimum growth at pH 7.8. Growth was not observed at or below 40 6C, at or above 84 6C, at or below pH 5.4 or at or above pH 9.5. The isolate degraded a wide range of substrates including starch, cellulose and cellulose derivatives. Elemental sulfur stimulated growth, but sodium sulfate, sulfite and thiosulfate did not. DNA G+C content was 31 mol%. Phylogenetic analysis of 16S rRNA gene sequences showed that strain 1445t T belonged to the genus Fervidobacterium. 16S rRNA gene sequence similarities with strains of other species of the genus Fervidobacterium were 94.9-98.3 %; the type strain of Fervidobacterium gondwanense was the closest relative of strain 1445t T

A strain of a hyperthermophilic filamentous archaeon was isolated from a sample of Kamchatka hot spring sediment. Isolate 1807-2 grew optimally at 85 °C, pH 6.0-6.5, the parameters being close to those at the sampling site. 16S rRNA gene sequence analysis placed the novel isolate in the crenarchaeal genus Thermofilum; Thermofilum pendens was its closest valid relative (95.7 % of sequence identity). Strain 1807-2 grew organothrophically using polysaccharides (starch and glucomannan), yeast extract or peptone as substrates. The addition of other crenarchaea culture broth filtrates was obligatory required for growth and could not be replaced by the addition of these organisms’ cell wall fractions, as it was described for T. pendens. The genome of strain 1807-2 was sequenced using Illumina and PGM technologies. The average nucleotide identities between genome of strain 1807-2 and T. pendens strain HRK 5T and “T. adornatus” strain 1910b were 85 and 82 %, respectively. On the basis of 16S rRNA gene sequence phylogeny, ANI calculations and phenotypic differences we propose a novel species Thermofilum uzonense with the type strain 1807-2T (= DSM 28062T = JCM 19810T). Project information and genome sequence was deposited in Genbank under IDs PRJNA262459 and CP009961, respectively.Electronic supplementary materialThe online version of this article (doi:10.1186/s40793-015-0105-y) contains supplementary material, which is available to authorized users.