Thiomicrorhabdus sediminis sp. nov. and Thiomicrorhabdus xiamenensis sp. nov., novel sulfur-oxidizing bacteria isolated from coastal sediments and an emended description of the genus Thiomicrorhabdus.

Two novel Gram-strain-negative and rod-shaped bacteria, designated strain G1T and G2T, were isolated from sediment samples collected from the coast of Xiamen, PR China. The cells were motile by a single polar flagellum. Growth of strain G1T occurred at 10-40 °C (optimum, 30 °C), at pH 6.0-9.0 (optimum, pH 7.5) and with 5-1530 mM NaCl (optimum, 510 mM), while the temperature, pH and NaCl concentration ranges for G2T were 4-45 °C (optimum, 28 °C), pH 5.5-8.0 (optimum, pH 6.5) and 85-1530 mM NaCl (optimum, 340 mM). The two isolates were obligate chemolithoautotrophs capable of using thiosulfate, sulfide, elemental sulphur or tetrathionate as an energy source. Strain G1T used molecular oxygen or nitrite as an electron acceptor, while strain G2T used molecular oxygen as the sole electron acceptor. The dominant fatty acids of G1T and G2T were summed feature 3 (C16:1 ω7c and/or C16:1 ω6c), C16 : 0 and summed feature 8 (C18:1 ω7c and/or C18:1 ω6c). The DNA G+C content of G1T and G2T were 45.1 and 48.3 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain G1T and G2T were members of the genus Thiomicrorhabdus, and most closely related to Thiomicrorhabdus hydrogeniphila MAS2T (96.0 %) and Thiomicrorhabdus indica 13-15AT (95.4 %), respectively. The 16S rRNA gene sequence similarity between strains G1T and G2T was 95.8 %. Based on the phylogenetic, genomic and phenotypic data presented here, the isolate strains represent novel species of the genus Thiomicrorhabdus, for which the names Thiomicrorhabdus sediminis sp. nov. (type strain G1T=MCCC 1A14511T=KCTC 15841T) and Thiomicrorhabdus xiamenensis sp. nov. (type strain G2T=MCCC 1A14512T=KCTC 15842T) are proposed.

Thiosulfativibrio zosterae gen. nov., sp. nov., and Thiosulfatimonas sediminis gen. nov., sp. nov.

Aerobic, Gram-stain-negative, obligately chemolithoautotrophic thiosulfate-oxidizing bacteria, strains AkT22T and aks77T were isolated from a brackish lake in Japan. Strains AkT22T and aks77T were isolated from samples of eelgrass and sediment, respectively. Growth on sulfide, tetrathionate, elemental sulfur, and organic substrates was not observed for both strains. Growth of the strains was observed at 5 °C or higher temperature, with optimum growth at 22 °C. Strain AkT22T grew at a pH range of 5.8-8.0, with optimum growth at pH 6.7-7.8. Strain aks77T grew at a pH range of 5.8-8.5, with optimum growth at pH 7.0-7.9. Major cellular fatty acids (> 10% of total) of strain AkT22T were C16:1, C18:1, and C16:0. The sole respiratory quinone was ubiquinone-8 in both strains. The genome of strain AkT22T consisted of a circular chromosome, with size of approximately 2.6 Mbp and G + C content of 43.2%. Those values of the genome of strain aks77T were ca. 2.7 Mbp and 45.5%, respectively. Among cultured bacteria, Thiomicrorhabdus aquaedulcis HaS4T showed the highest sequence identities of the 16S rRNA gene, to strains AkT22T (94%) and aks77T (95%). On the basis of these results, Thiosulfativibrio zosterae gen. nov., sp. nov. and Thiosulfatimonas sediminis gen. nov., sp. nov. are proposed, with type strains of AkT22T (= BCRC 81184T = NBRC 114012T = DSM 109948T) and aks77T (= BCRC 81183T = NBRC 114013T), respectively.

Thiomicrorhabdus indica sp. nov., an obligately chemolithoautotrophic, sulfur-oxidizing bacterium isolated from a deep-sea hydrothermal vent environment.

A new mesophilic bacterium, designated strain 13-15AT, was isolated from the deep-sea water from the Carlsberg Ridge, northwestern Indian Ocean. Cells were short rods and motile with a single polar flagellum. Growth was observed in the presence of 85-1700 mM NaCl (optimum 680 mM), at 10-45 °C (optimum, 28 °C) and pH 5.0-9.0 (optimum, pH 7.0). The isolate was an obligate chemolithoautotroph capable of growth using thiosulfate, sulfide, elemental sulfur or tetrathionate as the sole energy source, carbon dioxide as the sole carbon source, and molecular oxygen as the sole electron acceptor. Molecular hydrogen did not support growth. The major fatty acids were C16 : 1 (45.0 %), C18 : 1 (22.5 %) and C16 : 0 (20.1 %). The G+C content of the genomic DNA was 41.6 mol%. The results of phylogenetic analysis based on 16S rRNA gene sequences showed that the novel isolate belonged to the genus Thiomicrorhabdus and was most closely related to Thiomicrorhabdus hydrogeniphila MAS2T (94.8 % sequence similarity). On the basis of the taxonomic data obtained in this study, strain 13-15AT represents a novel species of the genus Thiomicrorhabdus, for which the name Thiomicrorhabdus indica sp. nov. is proposed, with the type strain 13-15AT (=MCCC 1A13986T=KCTC 15750T).

Thiomicrorhabdus aquaedulcis sp. nov., a sulfur-oxidizing bacterium isolated from lake water.

Strain HaS4T is an aerobic sulfur-oxidizing bacterium isolated from water of Lake Harutori in Japan. It was isolated and partially characterized in a previous study, but its taxonomic status has not been determined. The previous study revealed that the strain is an obligate chemolithoautotroph which grows at temperatures ranging from 0 to 25 °C (optimum, 22 °C) and pH from pH 6.2 to 8.8 (optimum, pH 6.6-7.4). In this study, further characterization of the strain was made to describe it as representative of a novel species. Cells of strain HaS4T are rod-shaped, 1.6-2.5 µm long, 0.7-0.9 µm wide and Gram-stain-negative. Major cellular fatty acids were summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C16 : 0. Phylogenetic analysis based on the 16S rRNA gene indicated that the strain is related to the genus Thiomicrorhabdus, but phylogenetically distinct from the type strains of existing species in the genus. On the basis of its phylogenetic and phenotypic properties, strain HaS4T (=NBRC 112315T=BCRC 81110T) is proposed as type strain of a new non-marine species of the genus Thiomicrorhabdus with the name Thiomicrorhabdus aquaedulcis sp. nov.

Horizontal acquisition of hydrogen conversion ability and other habitat adaptations in the Hydrogenovibrio strains SP-41 and XCL-2.

BACKGROUND: Obligate sulfur oxidizing chemolithoauthotrophic strains of Hydrogenovibrio crunogenus have been isolated from multiple hydrothermal vent associated habitats. However, a hydrogenase gene cluster (encoding the hydrogen converting enzyme and its maturation/assembly machinery) detected on the first sequenced H. crunogenus strain (XCL-2) suggested that hydrogen conversion may also play a role in this organism. Yet, numerous experiments have underlined XCL-2's inability to consume hydrogen under the tested conditions. A recent study showed that the closely related strain SP-41 contains a homolog of the XCL-2 hydrogenase (a group 1b [NiFe]-hydrogenase), but that it can indeed use hydrogen. Hence, the question remained unresolved, why SP-41 is capable of using hydrogen, while XCL-2 is not. RESULTS: Here, we present the genome sequence of the SP-41 strain and compare it to that of the XCL-2 strain. We show that the chromosome of SP-41 codes for a further hydrogenase gene cluster, including two additional hydrogenases: the first appears to be a group 1d periplasmic membrane-anchored hydrogenase, and the second a group 2b sensory hydrogenase. The region where these genes are located was likely acquired horizontally and exhibits similarity to other Hydrogenovibrio species (H. thermophilus MA2-6 and H. marinus MH-110 T) and other hydrogen oxidizing Proteobacteria (Cupriavidus necator H16 and Ghiorsea bivora TAG-1 T). The genomes of XCL-2 and SP-41 show a strong conservation in gene order. However, several short genomic regions are not contained in the genome of the other strain. These exclusive regions are often associated with signs of DNA mobility, such as genes coding for transposases. They code for transport systems and/or extend the metabolic potential of the strains. CONCLUSIONS: Our results suggest that horizontal gene transfer plays an important role in shaping the genomes of these strains, as a likely mechanism for habitat adaptation, including, but not limited to the transfer of the hydrogen conversion ability.

Diversity in CO2-Concentrating Mechanisms among Chemolithoautotrophs from the Genera Hydrogenovibrio, Thiomicrorhabdus, and Thiomicrospira, Ubiquitous in Sulfidic Habitats Worldwide.

Members of the genera Hydrogenovibrio, Thiomicrospira, and Thiomicrorhabdus fix carbon at hydrothermal vents, coastal sediments, hypersaline lakes, and other sulfidic habitats. The genome sequences of these ubiquitous and prolific chemolithoautotrophs suggest a surprising diversity of mechanisms for the uptake and fixation of dissolved inorganic carbon (DIC); these mechanisms are verified here. Carboxysomes are apparent in the transmission electron micrographs of most of these organisms but are lacking in Thiomicrorhabdus sp. strain Milos-T2 and Thiomicrorhabdus arctica, and the inability of Thiomicrorhabdus sp. strain Milos-T2 to grow under low-DIC conditions is consistent with the absence of carboxysome loci in its genome. For the remaining organisms, genes encoding potential DIC transporters from four evolutionarily distinct families (Tcr_0853 and Tcr_0854, Chr, SbtA, and SulP) are located downstream of carboxysome loci. Transporter genes collocated with carboxysome loci, as well as some homologs located elsewhere on the chromosomes, had elevated transcript levels under low-DIC conditions, as assayed by reverse transcription-quantitative PCR (qRT-PCR). DIC uptake was measureable via silicone oil centrifugation when a representative of each of the four types of transporter was expressed in Escherichia coli The expression of these genes in the carbonic anhydrase-deficient E. coli strain EDCM636 enabled it to grow under low-DIC conditions, a result consistent with DIC transport by these proteins. The results from this study expand the range of DIC transporters within the SbtA and SulP transporter families, verify DIC uptake by transporters encoded by Tcr_0853 and Tcr_0854 and their homologs, and introduce DIC as a potential substrate for transporters from the Chr family.IMPORTANCE Autotrophic organisms take up and fix DIC, introducing carbon into the biological portion of the global carbon cycle. The mechanisms for DIC uptake and fixation by autotrophic Bacteria and Archaea are likely to be diverse but have been well characterized only for "Cyanobacteria" Based on genome sequences, members of the genera Hydrogenovibrio, Thiomicrospira, and Thiomicrorhabdus have a variety of mechanisms for DIC uptake and fixation. We verified that most of these organisms are capable of growing under low-DIC conditions, when they upregulate carboxysome loci and transporter genes collocated with these loci on their chromosomes. When these genes, which fall into four evolutionarily independent families of transporters, are expressed in E. coli, DIC transport is detected. This expansion in known DIC transporters across four families, from organisms from a variety of environments, provides insight into the ecophysiology of autotrophs, as well as a toolkit for engineering microorganisms for carbon-neutral biochemistries of industrial importance.

Genomes of ubiquitous marine and hypersaline Hydrogenovibrio, Thiomicrorhabdus and Thiomicrospira spp. encode a diversity of mechanisms to sustain chemolithoautotrophy in heterogeneous environments.

Chemolithoautotrophic bacteria from the genera Hydrogenovibrio, Thiomicrorhabdus and Thiomicrospira are common, sometimes dominant, isolates from sulfidic habitats including hydrothermal vents, soda and salt lakes and marine sediments. Their genome sequences confirm their membership in a deeply branching clade of the Gammaproteobacteria. Several adaptations to heterogeneous habitats are apparent. Their genomes include large numbers of genes for sensing and responding to their environment (EAL- and GGDEF-domain proteins and methyl-accepting chemotaxis proteins) despite their small sizes (2.1-3.1 Mbp). An array of sulfur-oxidizing complexes are encoded, likely to facilitate these organisms' use of multiple forms of reduced sulfur as electron donors. Hydrogenase genes are present in some taxa, including group 1d and 2b hydrogenases in Hydrogenovibrio marinus and H. thermophilus MA2-6, acquired via horizontal gene transfer. In addition to high-affinity cbb3 cytochrome c oxidase, some also encode cytochrome bd-type quinol oxidase or ba3 -type cytochrome c oxidase, which could facilitate growth under different oxygen tensions, or maintain redox balance. Carboxysome operons are present in most, with genes downstream encoding transporters from four evolutionarily distinct families, which may act with the carboxysomes to form CO2 concentrating mechanisms. These adaptations to habitat variability likely contribute to the cosmopolitan distribution of these organisms.

Reclassification of Thiomicrospira hydrogeniphila (Watsuji et al. 2016) to Thiomicrorhabdus hydrogeniphila comb. nov., with emended description of Thiomicrorhabdus (Boden et al., 2017).

The genus Thiomicrorhabdus (Tmr) in the Piskirickettsiaceae in the Thiotrichales of the Gammaproteobacteria contains four species of sulfur-oxidising obligate chemolithoautotroph with validly published names, all previously classified as Thiomicrospira (Tms) species. Here we demonstrate that Thiomicrospira hydrogeniphila, a recently published hydrogen-utilising chemolithoautotroph closely related to Thiomicrorhabdus frisia (type species of Thiomicrorhabdus) should be classified as a member of the genus Thiomicrorhabdus and not Thiomicrospira, as Thiomicrorhabdus hydrogeniphila comb. nov., on the basis of comparative physiology and morphology as well as 16S rRNA (rrs) gene identity of Tms. hydrogeniphila MAS2T being closer to that of Tmr. frisia JB-A2T (99.1 %) than to Tms. pelophila DSM 1534T (90.5 %) or Hydrogenovibrio marinus MH-110T (94.1 %), and on the basis of the topology of 16S rRNA gene maximum likelihood trees, which clearly place Tms. hydrogeniphila within the genus Thiomicrorhabdus. It was also noted that thiosulfate-grown Thiomicrorhabdus spp. can be distinguished from Thiomicrospira spp. or Hydrogenovibrio spp. on the basis of the 3 dominant fatty acids (C16 : 1, C18 : 1 and C16 : 0), and from other Thiomicrorhabdus spp. on the basis of the fourth dominant fatty acid, which varies between the species of this genus - which could provide a useful diagnostic method. We provide an emended description of Thiomicrorhabdus (Boden R, Scott KM, Williams J, Russel S, Antonen K et al.Int J Syst Evol Microbiol 2017;67:1140-1151) to take into account the properties of Thiomicrorhabdus hydrogeniphila comb. nov.

Peculiar citric acid cycle of hydrothermal vent chemolithoautotroph Hydrogenovibrio crunogenus, and insights into carbon metabolism by obligate autotrophs.

The genome sequence of the obligate chemolithoautotroph Hydrogenovibrio crunogenus paradoxically predicts a complete oxidative citric acid cycle (CAC). This prediction was tested by multiple approaches including whole cell carbon assimilation to verify obligate autotrophy, phylogenetic analysis of CAC enzyme sequences and enzyme assays. Hydrogenovibrio crunogenus did not assimilate any of the organic compounds provided (acetate, succinate, glucose, yeast extract, tryptone). Enzyme activities confirmed that its CAC is mostly uncoupled from the NADH pool. 2-Oxoglutarate:ferredoxin oxidoreductase activity is absent, though pyruvate:ferredoxin oxidoreductase is present, indicating that sequence-based predictions of substrate for this oxidoreductase were incorrect, and that H. crunogenus may have an incomplete CAC. Though the H. crunogenus CAC genes encode uncommon enzymes, the taxonomic distribution of their top matches suggests that they were not horizontally acquired. Comparison of H. crunogenus CAC genes to those present in other 'Proteobacteria' reveals that H. crunogenus and other obligate autotrophs lack the functional redundancy for the steps of the CAC typical for facultative autotrophs and heterotrophs, providing another possible mechanism for obligate autotrophy.

An evaluation of Thiomicrospira, Hydrogenovibrio and Thioalkalimicrobium: reclassification of four species of Thiomicrospira to each Thiomicrorhabdus gen. nov. and Hydrogenovibrio, and reclassification of all four species of Thioalkalimicrobium to Thiomicrospira.

Thiomicrospira(Tms) species are small sulfur-oxidizing chemolithoautotrophic members of the Gammaproteobacteria. Whilst the type species Tms. pelophila and closely related Tms. thyasirae exhibit canonical spiral morphology under sub-optimal growth conditions, most species are vibrios or rods. The 16S rRNA gene diversity is vast, with identities as low as 91.6 % for Tms. pelophila versus Tms. frisia, for example. Thiomicrospira was examined with closely related genera Hydrogenovibrio and Thioalkalimicrobium and, to rationalize organisms on the basis of the 16S rRNA gene phylogeny, physiology and morphology, we reclassify Tms. kuenenii, Tms. crunogena, Tms. thermophila and Tms. halophila to Hydrogenovibrio kuenenii comb. nov., H. crunogenus corrig. comb. nov., H. thermophilus corrig. comb. nov. and H. halophilus corrig. comb. nov. We reclassify Tms. frisia, Tms. arctica, Tms. psychrophila and Tms. chilensis to Thiomicrorhabdus (Tmr) gen. nov., as Tmr. frisia comb. nov., Tmr. arctica comb. nov., Tmr. psychrophila comb. nov. and Tmr. chilensis comb. nov. - the type species of Thiomicrorhabdus is Tmr. frisia. We demonstrate that Thioalkalimicrobium species fall within the genus Thiomicrospira sensu stricto, thus reclassifying them as Tms. aerophila corrig. comb. nov., Tms. microaerophila corrig. comb. nov., Tms. cyclica corrig. comb. nov. and Tms. sibirica corrig. comb. nov. We provide emended descriptions of the genera Thiomicrospira and Hydrogenovibrio and of Tms. thyasirae.

In-situ incubation of iron-sulfur mineral reveals a diverse chemolithoautotrophic community and a new biogeochemical role for Thiomicrospira.

Sulfide mineral precipitation occurs at mid-ocean ridge (MOR) spreading centers, both in the form of plume particles and seafloor massive sulfide structures. A common constituent of MOR is the iron-bearing sulfide mineral pyrrhotite, which was chosen as a substrate for in-situ incubation studies in shallow waters of Catalina Island, CA to investigate the colonization of iron-oxidizing bacteria. Microbial community datasets were obtained from in-situ incubated pyrrhotite, allowing for direct comparison to microbial communities of iron-sulfides from active and inactive chimneys in deep-sea environments. Unclassified Gammaproteobacteria and Alphaproteobacteria (Magnetovibrio) largely dominated the bacterial community on pyrrhotite samples incubated in the water column while samples incubated at the surface sediment showed more even dominance by Deltaproteobacteria (Desulfobulbus), Gammaproteobacteria (Piscirickettsiaceae), Alphaproteobacteria (Rhodobacteraceae), and Bacteroidetes (Flavobacteriia). Cultivations that originated from pyrrhotite samples resulted in the enrichment of both, sheath-forming and stalk-forming Zetaproteobacteria. Additionally, a putative novel species of Thiomicrospira was isolated and shown to grow autotrophically with iron, indicating a new biogeochemical role for this ubiquitous microorganism.

Thiomicrospira hydrogeniphila sp. nov., an aerobic, hydrogen- and sulfur-oxidizing chemolithoautotroph isolated from a seawater tank containing a block of beef tallow.

A moderately psychrophilic, aerobic, hydrogen- and sulfur-oxidizing bacterium, designated strain MAS2T, was isolated from a tank containing coastal seawater from Tokyo Bay and a block of beef tallow added as organic material. Growth occurred under aerobic chemolithoautotrophic conditions in the presence of molecular hydrogen, thiosulfate, tetrathionate, elemental sulfur or sulfide as the sole energy source and bicarbonate as a carbon source. The isolate represented a Gram-staining-negative rod with a single polar flagellum and grew in artificial seawater medium with thiosulfate at 2-40 °C (optimum 30 °C). The isolate grew in media with thiosulfate at Na+ concentrations between 30 and 1380 mM (optimum 270 mM). MAS2T possessed C16 : 0, C16 : 1 and C18 : 1 as the major fatty acids. The G+C content of the genomic DNA was 39.6 mol%. The 16S rRNA gene sequence similarity analysis showed that the isolate represented a member of the genus Thiomicrospira within the class Gammaproteobacteria and was most closely related to Thiomicrospira frisia JB-A2T. On the basis of phenotypic and molecular properties, the isolate represents a novel species of the genus Thiomicrospira, for which the name Thiomicrospira hydrogeniphila sp. nov. is proposed (type strain, MAS2T=JCM 30760T=DSM 100274T).

A novel hydrogen oxidizer amidst the sulfur-oxidizing Thiomicrospira lineage.

Thiomicrospira species are ubiquitously found in various marine environments and appear particularly common in hydrothermal vent systems. Members of this lineage are commonly classified as sulfur-oxidizing chemolithoautotrophs. Although sequencing of Thiomicrospira crunogena's genome has revealed genes that encode enzymes for hydrogen uptake activity and for hydrogenase maturation and assembly, hydrogen uptake ability has so far not been reported for any Thiomicrospira species. We isolated a Thiomicrospira species (SP-41) from a deep sea hydrothermal vent and demonstrated that it can oxidize hydrogen. We show in vivo hydrogen consumption, hydrogen uptake activity in partially purified protein extracts and transcript abundance of hydrogenases during different growth stages. The ability of this strain to oxidize hydrogen opens up new perspectives with respect to the physiology of Thiomicrospira species that have been detected in hydrothermal vents and that have so far been exclusively associated with sulfur oxidation.

Role of methylotrophs in the degradation of hydrocarbons during the Deepwater Horizon oil spill.

The role of methylotrophic bacteria in the fate of the oil and gas released into the Gulf of Mexico during the Deepwater Horizon oil spill has been controversial, particularly in relation to whether organisms such as Methylophaga had contributed to the consumption of methane. Whereas methanotrophy remains unqualified in these organisms, recent work by our group using DNA-based stable-isotope probing coupled with cultivation-based methods has uncovered hydrocarbon-degrading Methylophaga. Recent findings have also shown that methylotrophs, including Methylophaga, were in a heightened state of metabolic activity within oil plume waters during the active phase of the spill. Taken collectively, these findings suggest that members of this group may have participated in the degradation of high-molecular-weight hydrocarbons in plume waters. The discovery of hydrocarbon-degrading Methylophaga also highlights the importance of considering these organisms in playing a role to the fate of oil hydrocarbons at oil-impacted sites.

Methylophaga nitratireducenticrescens sp. nov. and Methylophaga frappieri sp. nov., isolated from the biofilm of the methanol-fed denitrification system treating the seawater at the Montreal Biodome.

Two bacterial strains, designated JAM1(T) and JAM7(T), were isolated from a methanol-fed denitrification system treating seawater at the Montreal Biodome, Canada. They were affiliated within the genus Methylophaga of the Gammaproteobacteria by analysis of the 16S rRNA gene sequences. Strain JAM1(T) had the capacity to grow under denitrifying conditions by reducing nitrate into nitrite which is unique among the species of the genus Methylophaga. Major fatty acids were C16:1ω7c or ω6c, C16:0 and C18:1ω7c or ω6c. The major ubiquinone was Q8. Both strains required vitamin B12 and Na(+) ions for growth. The genomes of strains JAM1(T) and JAM7(T) have been completely sequenced and showed a DNA G+C content of 44.7 mol% and 47.8 mol%, respectively. Growth occurred at pH 6-11 and at 0.5-8% NaCl. Both genomes contained predicted ORFs encoding the key enzymes of the ribulose monophosphate pathway. Also, operons encoding two nitrate reductases (Nar), two nitric oxide reductases (Nor), one nitrous oxide reductase (Nos) and one truncated nitrite reductase (NirK) were clustered in a 67 kb chromosomal region in strain JAM1(T). No such operons were found in strain JAM7(T). These results supported the affiliation of the two strains as novel species within the genus Methylophaga. The names Methylophaga nitratireducenticrescens sp. nov. for type strain JAM1(T) (=DSM 25689(T)=ATCC BAA-2433(T)) and Methylophaga frappieri sp. nov. for type strain JAM7(T) (=DSM 25690(T)=ATCC BAA-2434(T)) are proposed.

Galenea microaerophila gen. nov., sp. nov., a mesophilic, microaerophilic, chemosynthetic, thiosulfate-oxidizing bacterium isolated from a shallow-water hydrothermal vent.

A mesophilic, strictly microaerophilic, chemosynthetic bacterium, designated strain P2D(T), was isolated from the sediment of an active shallow-water hydrothermal vent in Paleochori Bay, on the Greek island of Milos. The cells were Gram-staining-negative rods that measured approximately 0.8-1.3 µm in length and 0.4-0.5 µm in width. Strain P2D(T) grew at 20-50 °C (optimum 35 °C), with 1.0-5.0% (w/v) NaCl (optimum 3.0%), and at pH 4.5-8.0 (optimum pH 5.5). The generation time under optimal conditions was 1.1 h. Growth occurred under chemolithoautotrophic conditions with S2O3²â» and CO(2) as the energy and carbon sources, respectively. Oxygen (5%) was used as sole terminal electron acceptor. No growth was observed in the presence of acetate, formate, lactate, tryptone or peptone. Chemolithoheterotrophic growth occurred when d-glucose or sucrose were present as carbon sources. None of the organic compounds tested was used as an electron donor. The genomic DNA G+C content of the novel strain was 44.9 mol%. In a phylogenetic analysis based on 16S rRNA gene sequences, strain P2D(T) was found to be most closely related to Thiomicrospira psychrophila DSM 13453(T) (92.8% sequence similarity). Based on the phylogenetic, physiological and chemotaxonomic evidence, strain P2D(T) represents a novel species of a new genus within the class Gammaproteobacteria of the family Piscirickettsiaceae, for which the name Galenea microaerophila gen. nov., sp. nov. is proposed. The type strain of the type species is P2D(T) ( = DSM 24963(T) = JCM 17795(T)).

Emended description of the genus Methylophaga Janvier et al. 1985.

The genus Methylophaga Janvier et al. 1985 comprises eight species with validly published names at the time of writing. The original description of the genus was published over 26 years ago and was based on only two species, namely Methylophaga marina and Methylophaga thalassica - as such, the description of the genus requires updating to take into account the other six known species. Based on literature concerning the eight species of Methylophaga published over the last 26 years, an emended description of the genus is presented, taking into account properties of all members of the species with validly published names.

Methylophaga lonarensis sp. nov., a moderately haloalkaliphilic methylotroph isolated from the soda lake sediments of a meteorite impact crater.

A moderately haloalkaliphilic methylotrophic bacterium possessing the ribulose monophosphate pathway for carbon assimilation, designated MPL(T), was isolated from Lonar Lake sediment microcosms that were oxidizing methane for two weeks. The isolate utilized methanol and was an aerobic, Gram-negative, asporogenous, motile, short rod that multiplied by binary fission. The isolate required NaHCO(3) or NaCl for growth and, although not auxotrophic for vitamin B(12), had enhanced growth with vitamin B(12). Optimal growth occurred with 0.5-2% (w/v) NaCl, at 28-30 °C and at pH 9.0-10.0. The cellular fatty acid profile consisted primarily of straight-chain saturated C(16:0) and unsaturated C(16:1)ω7c and C(18:1)ω7c. The major ubiquinone was Q-8. The dominant phospholipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. Cells accumulated ectoine as the main compatible solute. The DNA G+C content was 50.0 mol%. The isolate exhibited 94.0-95.4% 16S rRNA gene sequence similarity with the type strains of methylotrophs belonging to the genus Methylophaga and 31% DNA-DNA relatedness with the reference strain, Methylophaga alcalica VKM B-2251(T). It is proposed that strain MPL(T) represents a novel species, Methylophaga lonarensis sp. nov. (type strain MPL(T)=VKM B-2684(T)=MCC 1002(T)).

Draft genome sequence of Methylophaga aminisulfidivorans MP T.

Methylophaga aminisulfidivorans MP(T) is a restricted facultatively marine methylotrophic bacterium that grows on methanol, methylated amines, dimethyl sulfide, and dimethyl sulfoxide. Here we present the high-quality draft genome sequence of M. aminisulfidivorans MP(T) (KCTC 12909(T) = JCM 14647(T)), consisting of a chromosome (3,092,085 bp) and a plasmid (16,875 bp).

Metagenomic comparison of two Thiomicrospira lineages inhabiting contrasting deep-sea hydrothermal environments.

BACKGROUND: The most widespread bacteria in oxic zones of carbonate chimneys at the serpentinite-hosted Lost City hydrothermal field, Mid-Atlantic Ridge, belong to the Thiomicrospira group of sulfur-oxidizing chemolithoautotrophs. It is unclear why Thiomicrospira-like organisms thrive in these chimneys considering that Lost City hydrothermal fluids are notably lacking in hydrogen sulfide and carbon dioxide. METHODOLOGY/PRINCIPAL FINDINGS: Here we describe metagenomic sequences obtained from a Lost City carbonate chimney that are highly similar to the genome of Thiomicrospira crunogena XCL-2, an isolate from a basalt-hosted hydrothermal vent in the Pacific Ocean. Even though T. crunogena and Lost City Thiomicrospira inhabit different types of hydrothermal systems in different oceans, their genomic contents are highly similar. For example, sequences encoding the sulfur oxidation and carbon fixation pathways (including a carbon concentration mechanism) of T. crunogena are also present in the Lost City metagenome. Comparative genomic analyses also revealed substantial genomic changes that must have occurred since the divergence of the two lineages, including large genomic rearrangements, gene fusion events, a prophage insertion, and transposase activity. CONCLUSIONS/SIGNIFICANCE: Our results show significant genomic similarity between Thiomicrospira organisms inhabiting different kinds of hydrothermal systems in different oceans, suggesting that these organisms are widespread and highly adaptable. These data also indicate genomic processes potentially associated with the adaptation of these lineages into strikingly different habitats.