Xiang Zeng

Pyrococcus CH1, an obligate piezophilic hyperthermophile: extending the upper pressure-temperature limits for life

A novel hydrothermal site was discovered in March 2007, on the mid-Atlantic ridge during the cruise ‘Serpentine’. At a depth of 4100 m, the site ‘Ashadze’ is the deepest vent field known so far. Smoker samples were collected with the ROV ‘Victor 6000’ and processed in the laboratory for the enrichment of anaerobic heterotrophic microorganisms under high-temperature and high-hydrostatic pressure conditions. Strain CH1 was successfully isolated and assigned to the genus Pyrococcus, within the Euryarchaeota lineage within the Archaea domain. This organism grows within a temperature range of 80 to 108 °C and a pressure range of 20 to 120 MPa, with optima for 98 °C and 52 MPa respectively. Pyrococcus CH1 represents the first obligate piezophilic hyperthermophilic microorganism known so far. Comparisons of growth yields obtained under high-temperature/high-pressure conditions for relative organisms isolated from various depths, showed clear relationships between depth at origin and responses to hydrostatic pressure.

Pseudodesulfovibrio indicus gen. nov., sp. nov., a piezophilic sulfate-reducing bacterium from the Indian Ocean and reclassification of four species of the genus Desulfovibrio.

A novel sulfate-reducing bacterium, strain J2T, was isolated from a serpentinized peridotite sample from the Indian Ocean. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain J2T clustered with the genus Desulfovibrio within the family Desulfovibrionaceae, but it showed low similarity (87.95 %) to the type species Desulfovibrio desulfuricans DSM 642T. It was most closely related to Desulfovibrio portus MSL79T (96.96 %), followed by Desulfovibrio aespoeensis Aspo-2T (96.11 %), Desulfovibrio piezophilus C1TLV30T (96.04 %) and Desulfovibrio profundus DSM 11384T (95.17 %). Other available sequences shared less than 93.33 % 16S rRNA gene sequence similarity. Cells were Gram-staining-negative, anaerobic, motile vibrios (2-6×0.4-0.6 µm). Growth was observed at salinities ranging from 0.2 to 6 % (optimum 2.5 %), from pH 5 to 8 (optimum pH 6.5-7) and at temperatures between 9 and 40 °C (optimum 30-35 °C). J2T was piezophilic, growing optimally at 10 MPa (range 0-30 MPa). J2T used lactate, malate, pyruvate, formate and hydrogen as energy sources. Sulfate, thiosulfate, sulfite, fumarate and nitrate were used as terminal electron acceptors. Lactate and pyruvate were fermented. The main fatty acids were iso-C15 : 0, anteiso-C15 : 0, summed feature 9 (iso-C17 : 1ω9c and/or C16 : 0 10-methyl) and iso-C17 : 0. The DNA G+C content of strain J2T was 63.5 mol%. The combined genotypic and phenotypic data show that strain J2T represents a novel species of a novel genus in the family Desulfovibrionaceae, for which the name Pseudodesulfovibrio indicus gen. nov., sp. nov. is proposed, with the type strain J2T (=MCCC 1A01867T = DSM 101483T). We also propose the reclassification of D. piezophilus as Pseudodesulfovibrio piezophilus comb. nov., D. profundus as Pseudodesulfovibrio profundus comb. nov., D. portus as Pseudodesulfovibrio portus comb. nov. and D. aespoeensis as Pseudodesulfovibrio aespoeensis comb. nov.

Thermophilic hydrogen-producing bacteria inhabiting deep-sea hydrothermal environments represented by Caloranaerobacter.

Hydrogen is an important energy source for deep-sea hydrothermal vent ecosystems. However, little is known about microbes and their role in hydrogen turnover in the environment. In this study, the diversity and physiological characteristics of fermentative hydrogen-producing microbes from deep-sea hydrothermal vent fields were described for the first time. Seven enrichments were obtained from hydrothermal vent sulfides collected from the Southwest Indian Ocean, East Pacific and South Atlantic. 16S rRNA gene analysis revealed that members of the Caloranaerobacter genus were the dominant component in these enrichments. Subsequently, three thermophilic hydrogen producers, strains H363, H53214 and DY22619, were isolated. They were phylogenetically related to species of the genus Caloranaerobacter. The H2 yields of strains H363, H53214, DY22619 and MV107, which was the type species of genus Caloranaerobacter, were 0.11, 1.21, 3.13 and 2.85 mol H2/mol glucose, respectively. Determination of the main soluble metabolites revealed that strains H363, H53214 and MV107 performed heterolactic fermentations, while strain DY22619 performed butyric acid fermentation, indicating distinct fermentation patterns among members of the genus. Finally, a diversity of forms of [FeFe]-hydrogenase with different modular structures was revealed based on draft genomic data of Caloranaerobacter strains. This highlights the complexity of hydrogen metabolism in Caloranaerobacter, reflecting adaptations to environmental conditions in hydrothermal vent systems. Collectively, results suggested that Caloranaerobacter species might be ubiquitous and play a role in biological hydrogen generation in deep-sea hydrothermal vent fields.

Caloranaerobacter ferrireducens sp. nov., an anaerobic, thermophilic, iron (III)-reducing bacterium isolated from deep-sea hydrothermal sulfide deposits

A thermophilic, anaerobic, iron-reducing bacterium (strain DY22619T) was isolated from a sulfide sample collected from an East Pacific Ocean hydrothermal field at a depth of 2901 m. Cells were Gram-stain-negative, motile rods (2-10 µm in length, 0.5 µm in width) with multiple peritrichous flagella. The strain grew at 40-70 °C inclusive (optimum 60 °C), at pH 4.5-8.5 inclusive (optimum pH 7.0) and with sea salts concentrations of 1-10 % (w/v) (optimum 3 % sea salts) and NaCl concentrations of 1.5-5.0 % (w/v) (optimum 2.5 % NaCl). Under optimal growth conditions, the generation time was around 55 min. The isolate was an obligate chemoorganoheterotroph, utilizing complex organic compounds, amino acids, carbohydrates and organic acids including peptone, tryptone, beef extract, yeast extract, alanine, glutamate, methionine, threonine, fructose, mannose, galactose, glucose, palatinose, rhamnose, turanose, gentiobiose, xylose, sorbose, pyruvate, tartaric acid, α-ketobutyric acid, α-ketovaleric acid, galacturonic acid and glucosaminic acid. Strain DY22619T was strictly anaerobic and facultatively dependent on various forms of Fe(III) as an electron acceptor: insoluble forms and soluble forms. It did not reduce sulfite, sulfate, thiosulfate or nitrate. The genomic DNA G+C content was 29.0 mol%. Phylogenetic 16S rRNA gene sequence analyses revealed that the closest relative of strain DY22619T was Caloranaerobacter azorensis MV1087T, sharing 97.41 % 16S rRNA gene sequence similarity. On the basis of physiological distinctness and phylogenetic distance, the isolate is considered to represent a novel species of the genus Caloranaerobacter, for which the name Caloranaerobacterhttp://dx.doi.org/10.1601/nm.4081ferrireducens sp. nov. is proposed. The type strain is DY22619T ( = JCM 19467T = DSM 27799T = MCCC1A06455T).

Anoxybacter fermentans gen. nov., sp. nov., a piezophilic, thermophilic, anaerobic, fermentative bacterium isolated from a deep-sea hydrothermal vent.

A novel piezophilic, thermophilic, anaerobic, fermentative bacterial strain, designated strain DY22613(T), was isolated from a deep-sea hydrothermal sulfide deposit at the East Pacific Rise (GPS position: 102.6° W 3.1° S). Cells of strain DY22613(T) were long, motile rods (10 to 20 µm in length and 0.5 µm in width) with peritrichous flagella and were Gram-stain-negative. Growth was recorded at 44-72 °C (optimum 60-62 °C) and at hydrostatic pressures of 0.1-55 MPa (optimum 20 MPa). The pH range for growth was from pH 5.0 to 9.0 with an optimum at pH 7.0. Growth was observed in the presence of 1 to 8 % (w/v) sea salts and 0.65 to 5.2 % (w/v) NaCl, with optimum salt concentrations at 3.5 % for sea salts and at 2.3 % for NaCl. Under optimal growth conditions, the shortest generation time observed was 27 min (60 °C, 20 MPa). Strain DY22613(T) was heterotrophic, able to utilize complex organic compounds, amino acids, sugars and organic acids including peptone, tryptone, beef extract, yeast extract, alanine, glutamine, methionine, phenylalanine, serine, threonine, fructose, fucose, galactose, gentiobiose, glucose, mannose, melibiose, palatinose, rhamnose, turanose, pyruvate, lactic acid, methyl ester, erythritol, galacturonic acid and glucosaminic acid. Strain DY22613(T) was able to reduce Fe(III) compounds, including Fe(III) oxyhydroxide (pH 7.0), amorphous iron(III) oxide (pH 9.0), goethite (α-FeOOH, pH 12.0), Fe(III) citrate and elementary sulfur. Products of fermentation were butyrate, acetate and hydrogen. Main cellular fatty acids were iso-C15 : 0, iso-C14 : 0 3-OH and C14 : 0. The genomic DNA G+C content of strain DY22613(T) was 36.7 mol%. Based on 16S rRNA gene sequence analysis, the strain forms a novel lineage within the class Clostridia and clusters with the order Haloanaerobiales (86.92 % 16S rRNA gene sequence similarity). The phylogenetic data suggest that the lineage represents at least a novel genus and species, for which the name Anoxybacter fermentans gen. nov., sp. nov. is proposed. The type strain is DY22613(T) ( = JCM 19466(T) = DSM 28033(T) = MCCC 1A06456(T)).

Wukongibacter baidiensis gen. nov., sp. nov., an anaerobic bacterium isolated from hydrothermal sulfides, and proposal for the reclassification of the closely related Clostridium halophilum and Clostridium caminithermale within Maledivibacter gen. nov. and Paramaledivibacter gen. nov., respectively.

An anaerobic, Gram-stain-positive, spore-forming bacterium, designated DY30321T, was isolated from a sample of mixed hydrothermal sulfides collected during cruise DY30 of R/V Da Yang Yi Hao. Cells of strain DY30321T were rod-shaped with rounded ends, and were not motile. Strain DY30321T grew optimally at pH 8.0, at 30 °C and at a salinity (sea salts) of 30-40 g l-1. The principal fatty acids of strain DY30321T were C14 : 0 and summed feature 1 (comprising iso H-C15 : 1/C13 : 0 3-OH). The predominant polar lipids of strain DY30321T were diphosphatidylglycerol, phosphatidylcholine and phosphatidylethanolamine. No respiratory quinone was detected. The G+C content of the genomic DNA of strain DY30321T was 33.4 mol%. Phylogenetically, strain DY30321T branched within the family Peptostreptococcaceae, with (misclassified) Clostridium halophilum M1T being its closest phylogenetic relative (94.6 % 16S rRNA gene sequence similarity), followed by (misclassified) Clostridium caminithermale DVird3T (92.1 %). These strains showed very low 16S rRNA gene sequence similarity (<84 %) to Clostrdium butyricum ATCC 19398T, the type species of the genus Clostridium sensu stricto. On the basis of its phenotypic, phylogenetic and chemotaxonomic characteristics, strain DY30321T (=KCTC 15549T=MCCC 1A01532T) is considered as the type strain of a novel species of a new genus in the family Peptostreptococcaceae, for which the name Wukongibacterbaidiensis gen. nov., sp. nov. is proposed. Maledivibacter gen. nov. is proposed to accommodate Clostridium halophilum as Maledivibacter halophilus comb. nov. (type species of the genus), and Paramaledivibacter gen. nov. to accommodate Clostridium caminithermale as Paramaledivibacter caminithermalis comb. nov. (type species of the genus).

Mameliella atlantica sp. nov., a marine bacterium of the Roseobacter clade isolated from deep-sea sediment of the South Atlantic Ocean

A taxonomic study was carried out on strain L6M1-5(T), which was isolated from deep-sea sediment collected from the South Atlantic Ocean. The isolate was Gram-reaction-negative, oxidase-negative and catalase-weakly positive. Growth was observed in the presence of 0.5-15% (w/v) NaCl (optimum 3-5%), at 10-41 °C (optimum 28-30 °C), and pH 5.0-10.5 (optimum pH 7.0). The principal fatty acids were summed feature 8 (C18 : 1ω7c/ω6c) (84.2%), C18 : 0 (6.3%), C12 : 1 3-OH (3.2%) and C16 : 0 (2.7%). The polar lipid profile comprised phosphatidylethanolamine, phosphatidylglycerol, two unidentified aminolipids, two unknown phospholipids and one unknown lipid. Ubiquinone-10 was the major quinone. The G+C content of the genomic DNA was 66.0 mol %. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain L6M1-5(T) belonged to the genus Mameliella and shared 95.8% sequence similarity with Mameliella alba JLT354-W(T). The combined genotypic and phenotypic data show that strain L6M1-5(T) represents a novel species of the genus Mameliella, for which the name Mameliella. atlantica sp. nov. is proposed. The type strain is L6M1-5(T) ( = MCCC 1A07531(T) = JCM 30230(T)).

Anaeromicrobium sediminis gen. nov., sp. nov., a fermentative bacterium isolated from deep-sea sediment

A novel anaerobic, mesophilic, heterotrophic bacterium, designated strain DY2726DT, was isolated from West Pacific Ocean sediments. Cells were long rods (0.5-0.8 µm wide, 4-15 µm long), Gram-positive and motile by means of flagella. The temperature and pH ranges for growth were 25-40 °C and pH 6.5-9.0, while optimal growth occurred at 37 °C and pH 7.5, with a generation time of 76 min. The strain required sea salts for growth at concentrations from 10 to 30 g l-1 (optimum at 20 g l-1). Substrates used as carbon sources were yeast extract, tryptone, glucose, cellobiose, starch, gelatin, dextrin, fructose, fucose, galactose, galacturonic acid, gentiobiose, glucosaminic acid, mannose, melibiose, palatinose and rhamnose. Products of fermentation were carbon dioxide, acetic acid and butyric acid. Strain DY2726DT was able to reduce amorphous iron hydroxide, goethite, amorphous iron oxides, anthraquinone-2,6-disulfonate and crotonate, but did not reduce sulfur, sulfate, thiosulfate, sulfite or nitrate. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain DY2726DT was affiliated to the family Clostridiaceae and was most closely related to the type strains of Alkaliphilus transvaalensis (90.0 % similarity) and Alkaliphilus oremlandii (89.6 %). The genomic DNA G+C content was 33.4 mol%. The major cellular fatty acids of strain DY2726DT were C16 : 1, C14 : 0 and C16 : 0. On the basis of its phenotypic and genotypic properties, strain DY2726DT is suggested to represent a novel species of a new genus in the family Clostridiaceae, for which the name Anaeromicrobium sediminis gen. nov., sp. nov. is proposed. The type strain of Anaeromicrobium sediminis is DY2726DT (=JCM 30224T=MCCC 1A00776T).

Complete Genome Sequence of Hyperthermophilic Piezophilic Archaeon Palaeococcus pacificus DY20341T, Isolated from Deep-Sea Hydrothermal Sediments

ABSTRACT We report the genome sequence of Palaeococcus pacificus DY20341T, isolated from a sediment sample collected from eastern Pacific Ocean hydrothermal fields, which is the first report of a complete genome for a Palaeococcus species. The genome sequence will help to better understand differentiation phylogenetic relationships and evolution of several Thermococcales species.