Helicovermis profundi gen. nov., sp. nov., a novel mesophilic, asporogenous bacterium within the Clostridia isolated from a deep-sea hydrothermal vent chimney

A novel mesophilic bacterial strain, designated S502T, was isolated from a deep-sea hydrothermal vent at Suiyo Seamount, Japan. Cells were Gram-positive, asporogenous, motile, and curved rods, measuring 1.6-5.6 µm in length. The strain was an obligate anaerobe that grew fermentatively on complex substrates such as yeast extract and Bacto peptone. Elemental sulfur stimulated the growth of the strain, and was reduced to hydrogen sulfide. The strain grew within a temperature range of 10-23 °C (optimum at 20 °C), pH range of 4.8-8.3 (optimum at 7.4), and a NaCl concentration range of 1.0-4.0% (w/v) (optimum at 3.0%, w/v). Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the isolate was a member of the class Clostridia, with Fusibacter paucivorans strain SEBR 4211T (91.1% sequence identity) being its closest relative. The total size of the genome of the strain was 3.12 Mbp, and a G + C content was 28.2 mol%. The highest values for average nucleotide identity (ANI), average amino acid identity (AAI), and digital DNA-DNA hybridization (dDDH) value of strain S502T with relatives were 67.5% (with Marinisporobacter balticus strain 59.4MT), 51.5% (with M. balticus strain 59.4MT), and 40.9% (with Alkaliphilus serpentinus strain LacTT), respectively. Based on a combination of phylogenetic, genomic, and phenotypic characteristics, we propose strain S502T to represent a novel genus and species, Helicovermis profundi gen. nov., sp. nov., with the type strain S502T (= DSM 112048T = JCM 39167T).

Crassaminicella thermophila sp. nov., a moderately thermophilic bacterium isolated from a deep-sea hydrothermal vent chimney and emended description of the genus Crassaminicella

A novel moderately thermophilic, anaerobic, heterotrophic bacterium (strain SY095^T) was isolated from a hydrothermal vent chimney located on the Southwest Indian Ridge at a depth of 2730 m. Cells were Gram-stain-positive, motile, straight to slightly curved rods forming terminal endospores. SY095^T was grown at 45-60 °C (optimum 50-55 °C), pH 6.0-7.5 (optimum 7.0), and in a salinity of 1-4.5 % (w/v) NaCl (optimum 2.5 %). Substrates utilized by SY095^T included fructose, glucose, maltose, N-acetyl glucosamine and tryptone. Casamino acid and amino acids (glutamate, glutamine, lysine, methionine, serine and histidine) were also utilized. The main end products from glucose fermentation were acetate, H₂ and CO₂. Elemental sulphur, sulphate, thiosulphate, sulphite, fumarate, nitrate, nitrite and Fe(III) were not used as terminal electron acceptors. The predominant cellular fatty acids were C_14 : 0 (60.5%) and C_16 : 0 (7.6 %). The main polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, five unidentified phospholipids and two unidentified aminophospholipids. No respiratory quinones were detected. The chromosomal DNA G+C content was 30.8 mol%. The results of phylogenetic analysis of the 16S rRNA gene sequences indicated that SY095^T was closely related to Crassaminicella profunda Ra1766H^T (95.8 % 16S rRNA gene sequence identity). SY095^T exhibited 78.1 % average nucleotide identity (ANI) to C. profunda Ra1766H^T. The in silico DNA-DNA hybridization (DDH) value indicated that SY095^T shared 22.7 % DNA relatedness with C. profunda Ra1766H^T. On the basis of its phenotypic, genotypic and phylogenetic characteristics, SY095^T is suggested to represent a novel species of the genus Crassaminicella, for which the name Crassaminicella thermophila sp. nov. is proposed. The type strain is SY095^T (=JCM 34213=MCCC 1K04191). An emended description of the genus Crassaminicella is also proposed.

Genome analysis of Crassaminicella sp. SY095, an anaerobic mesophilic marine bacterium isolated from a deep-sea hydrothermal vent on the Southwest Indian Ridge

Crassaminicella sp. strain SY095 is an anaerobic mesophilic marine bacterium that was recently isolated from a deep-sea hydrothermal vent on the Southwest Indian Ridge. Here, we present the complete genome sequence of strain SY095. The genome consists of a chromosome of 3,046,753 bp (G + C content of 30.81%) and a plasmid of 36,627 bp (G + C content of 31.29%), encodes 2966 protein, 135 tRNA genes, and 34 rRNA genes. Numerous genes are related to peptide transport, amino acid metabolism, motility, and sporulation. This agrees with the observation that strain SY095 is a spore-forming, motile, and chemoheterotrophic bacterium. Further, the genome harbors multiple prophages that carry all the genes necessary for viral particle synthesis. Some prophages carry additional genes that may be involved in the regulation of sporulation. This is the first reported genome of a bacterium from the genus Crassaminicella, providing insights into the microbial adaptation strategies to the deep-sea hydrothermal vent environment.

Revisiting the Evolution and Taxonomy of Clostridia, a Phylogenomic Update

Clostridium is a large genus of obligate anaerobes belonging to the Firmicutes phylum of bacteria, most of which have a Gram-positive cell wall structure. The genus includes significant human and animal pathogens, causative of potentially deadly diseases such as tetanus and botulism. Despite their relevance and many studies suggesting that they are not a monophyletic group, the taxonomy of the group has largely been neglected. Currently, species belonging to the genus are placed in the unnatural order defined as Clostridiales, which includes the class Clostridia. Here, we used genomic data from 779 strains to study the taxonomy and evolution of the group. This analysis allowed us to 1) confirm that the group is composed of more than one genus, 2) detect major differences between pathogens classified as a single species within the group of authentic Clostridium spp. (sensu stricto), 3) identify inconsistencies between taxonomy and toxin evolution that reflect on the pervasive misclassification of strains, and 4) identify differential traits within central metabolism of members of what has been defined earlier and confirmed by us as cluster I. Our analysis shows that the current taxonomic classification of Clostridium species hinders the prediction of functions and traits, suggests a new classification for this fascinating class of bacteria, and highlights the importance of phylogenomics for taxonomic studies.

Genome Analysis of Vallitalea guaymasensis Strain L81 Isolated from a Deep-Sea Hydrothermal Vent System

Abyssivirga alkaniphila strain L81T, recently isolated from a black smoker biofilm at the Loki’s Castle hydrothermal vent field, was previously described as a mesophilic, obligately anaerobic heterotroph able to ferment carbohydrates, peptides, and aliphatic hydrocarbons. The strain was classified as a new genus within the family Lachnospiraceae. Herein, its genome is analyzed and A. alkaniphila is reassigned to the genus Vallitalea as a new strain of V. guaymasensis, designated V. guaymasensis strain L81. The 6.4 Mbp genome contained 5651 protein encoding genes, whereof 4043 were given a functional prediction. Pathways for fermentation of mono-saccharides, di-saccharides, peptides, and amino acids were identified whereas a complete pathway for the fermentation of n-alkanes was not found. Growth on carbohydrates and proteinous compounds supported methane production in co-cultures with Methanoplanus limicola. Multiple confurcating hydrogen-producing hydrogenases, a putative bifurcating electron-transferring flavoprotein—butyryl-CoA dehydrogenase complex, and a Rnf-complex form a basis for the observed hydrogen-production and a putative reverse electron-transport in V. guaymasensis strain L81. Combined with the observation that n-alkanes did not support growth in co-cultures with M. limicola, it seemed more plausible that the previously observed degradation patterns of crude-oil in strain L81 are explained by unspecific activation and may represent a detoxification mechanism, representing an interesting ecological function. Genes encoding a capacity for polyketide synthesis, prophages, and resistance to antibiotics shows interactions with the co-occurring microorganisms. This study enlightens the function of the fermentative microorganisms from hydrothermal vents systems and adds valuable information on the bioprospecting potential emerging in deep-sea hydrothermal systems.

First Insights into the Genome of the Moderately Thermophilic Bacterium Clostridium tepidiprofundi SG 508T

The moderately thermophilic bacterium Clostridium tepidiprofundi is Gram-positive and belongs to clostridial cluster I. It was isolated from a hydrothermal vent chimney. Substrates utilized by C. tepidiprofundi include casein, peptone, tryptone, yeast extract, beef extract, starch, maltose, and glucose. The genome consists of one replicon (3.06 Mb).

Haloimpatiens lingqiaonensis gen. nov., sp. nov., an anaerobic bacterium isolated from paper-mill wastewater

An anaerobic bacterium, strain ZC-CMC3^T, was isolated from a wastewater sample in Zhejiang, China. Cells were Gram-stain-positive, peritrichous, non-spore-forming, rod-shaped (0.6-1.2 × 2.9-5.1 μm) and catalase- and oxidase-negative. Strain ZC-CMC3^T was able to grow at 25-48 °C (optimum 43 °C) and pH 5.5-8.0 (optimum pH 7.0). The NaCl concentration range for growth was 0-3 % (w/v) (optimum 0 %). The major polar lipids of the isolate were diphosphatidylglycerol, phosphatidylglycerol, several phospholipids and glycolipids. Main fermentation products from PYG medium were formate, acetate, lactate and ethanol. Substrates which could be utilized were peptone, tryptone, yeast extract and beef extract. No respiratory quinone was detected. The main fatty acids were C_14 : 0, C_16 : 0, C_16 : 1cis 7 and C_16 : 1cis 9. The DNA G+C content was 30.0 mol%. 16S rRNA gene sequence analysis revealed that the isolate belonged to the family Clostridiaceae. Phylogenetically, the most closely related species were Oceanirhabdus sediminicola NH-JN4^T (92.8 % 16S rRNA gene sequence similarity) and Clostridium tepidiprofundi SG 508^T (92.6 %). On the basis of phylogenetic, chemotaxonomic and phenotypic characteristics, strain ZC-CMC3^T represents a novel species of a new genus in the family Clostridiaceae, for which the name Haloimpatiens lingqiaonensis gen. nov., sp. nov. is proposed. The type strain of the type species is ZC-CMC3^T ( = KCTC 15321^T = JCM 19210^T = CCTCC AB 2013104^T).

Identification and quantification of the caproic acid-producing bacterium Clostridium kluyveri in the fermentation of pit mud used for Chinese strong-aroma type liquor production

Chinese strong-aroma type liquor (CSAL) is a popular distilled alcoholic beverage in China. It is produced by a complex fermentation process that is conducted in pits in the ground. Ethyl caproate is a key flavor compound in CSAL and is thought to originate from caproic acid produced by Clostridia inhabiting the fermentation pit mud. However, the particular species of Clostridium associated with this production are poorly understood and problematic to quantify by culturing. In this study, a total of 28 closest relatives including 15 Clostridia and 8 Bacilli species in pit muds from three CSAL distilleries, were detected by culture-dependent and -independent methods. Among them, Clostridium kluyveri was identified as the main producer of caproic acid. One representative strain C. kluyveri N6 could produce caproic, butyric and octanoic acids and their corresponding ethyl esters, contributing significantly to CSAL flavor. A real time quantitative PCR assay of C. kluyveri in pit muds developed showed that a concentration of 1.79×10(7) 16S rRNA gene copies/g pit mud in LZ-old pit was approximately six times higher than that in HLM and YH pits and sixty times higher than that in LZ-new pit respectively. This method can be used to improve the management of pit mud microbiology and its impact on CSAL quality.

Structural and biochemical studies of a moderately thermophilic exonuclease I from Methylocaldum szegediense

A novel exonuclease, designated as MszExo I, was cloned from Methylocaldum szegediense, a moderately thermophilic methanotroph. It specifically digests single-stranded DNA in the 3ʹ to 5ʹ direction. The protein is composed of 479 amino acids, and it shares 47% sequence identity with E. coli Exo I. The crystal structure of MszExo I was determined to a resolution of 2.2 Å and it aligns well with that of E. coli Exo I. Comparative studies revealed that MszExo I and E. coli Exo I have similar metal ion binding affinity and similar activity at mesophilic temperatures (25–47°C). However, the optimum working temperature of MszExo I is 10°C higher, and the melting temperature is more than 4°C higher as evaluated by both thermal inactivation assays and DSC measurements. More importantly, two thermal transitions during unfolding of MszExo I were monitored by DSC while only one transition was found in E. coli Exo I. Further analyses showed that magnesium ions not only confer structural stability, but also affect the unfolding of MszExo I. MszExo I is the first reported enzyme in the DNA repair systems of moderately thermophilic bacteria, which are predicted to have more efficient DNA repair systems than mesophilic ones.

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)).

Investigation of microbial community structure of a shallow lake after one season copper sulfate algaecide treatment

In present work we described, for the first time, the phylogenic structure of the microbial community in a shallow freshwater lake (Hawk Island Lake, located in the Lower Peninsula of the State of Michigan, U.S.A.) after one season (four times during May to August 2007) of CuSO₄ treatment for algae growth control. The microbial community structure was characterized by terminal restriction fragment length polymorphism (TRFLP), clone library and 454 pyrosequencing. The similar structure of water chemistry measured across three sampling sites suggested that the lake was well mixed. The concentration of chlorophyll a (chl-a) and turbidity was low, 3.35 ± 1.62 μg/L and 2.5 ± 1.9 NTU, respectively, implying that photosynthesis was suppressed. TRFLP profiles showed that the lake was dominated by 16 terminal fragments (TFs), accounting for 85.5-92.6% abundance. Analysis of similarity (ANOSIM) showed that the difference in microbial community structure between upper and lower depths of the water column was not significant (P=0.101). These results suggested that the microbial community structure within the lake was similar. Clone library and 454 pyrosequencing indicated that the lake was dominated by freshwater phyla, Proteobacteria, Bacteroides, and Actinobacteria. Moreover, the large number of unclassified bacteria (27.4% of total 2090,454 sequences) suggested a complex microbial community structure in the lake.

Oceanirhabdus sediminicola gen. nov., sp. nov., an anaerobic bacterium isolated from sea sediment

A novel anaerobic bacterium, designated NH-JN4(T) was isolated from a sediment sample collected in the South China Sea. Cells were Gram-stain-positive, spore-forming, peritrichous and rod-shaped (0.5-1.2×2.2-7 µm). The temperature and pH ranges for growth were 22-42 °C and pH 6.0-8.5. Optimal growth occurred at 34-38 °C and pH 6.5-7.0. The NaCl concentration range for growth was 0.5-6 % (w/v) with an optimum of 2.5 %. Catalase and oxidase were not produced. Substrates which could be utilized were peptone, tryptone, yeast extract, beef extract and glycine. Main fermentation products from PYG medium were formate, acetate, butyrate and ethanol. Strain NH-JN4(T) could utilize sodium sulfite as an electron acceptor. No respiratory quinone was detected. The predominant fatty acids were anteiso-C15 : 0, C16 : 0, iso-C15 : 0, anteiso-C17 : 0 and C16 : 0 DMA. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and glycolipids. The DNA G+C content was 35.8 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain NH-JN4(T) was a member of family Clostridiaceae, and was most closely related to Clostridium limosum ATCC 25620(T), Clostridium proteolyticum DSM 3090(T), Clostridium histolyticum ATCC 19401(T) and Clostridium tepidiprofundi SG 508(T), showing 94.0, 93.0, 92.9 and 92.3 % sequence similarity, respectively. On the basis of phenotypic, genotypic and chemotaxonomic properties, strain NH-JN4(T) represents a novel species of a new genus in the family Clostridiaceae, for which the name Oceanirhabdus sediminicola gen. nov., sp. nov. is proposed. The type strain of the type species is NH-JN4(T) ( = JCM 18501(T) = CCTCC AB 2013103(T) = KCTC 15322(T)).

Presence of glucose, xylose, and glycerol fermenting bacteria in the deep biosphere of the former Homestake gold mine, South Dakota

Eight fermentative bacterial strains were isolated from mixed enrichment cultures of a composite soil sample collected at 1.34 km depth from the former Homestake gold mine in Lead, SD, USA. Phylogenetic analysis of their 16S rRNA gene sequences revealed that these isolates were affiliated with the phylum Firmicutes belonging to genera Bacillus and Clostridium. Batch fermentation studies demonstrated that isolates had the ability to ferment glucose, xylose, or glycerol to industrially valuable products such as ethanol and 1,3-propanediol (PDO). Ethanol was detected as the major fermentation end product in glucose-fermenting cultures at pH 10 with yields of 0.205–0.304 g of ethanol/g of glucose. While a xylose-fermenting strain yielded 0.189 g of ethanol/g of xylose and 0.585 g of acetic acid/g of xylose at the end of fermentation. At pH 7, glycerol-fermenting isolates produced PDO (0.323–0.458 g of PDO/g of glycerol) and ethanol (0.284–0.350 g of ethanol/g of glycerol) as major end products while acetic acid and succinic acid were identified as minor by-products in fermentation broths. These results suggest that the deep biosphere of the former Homestake gold mine harbors bacterial strains which could be used in bio-based production of ethanol and PDO.

Hydrogen-producing microflora and Fe-Fe hydrogenase diversities in seaweed bed associated with marine hot springs of Kalianda, Indonesia

Microbial fermentation is a promising technology for hydrogen (H(2)) production. H(2) producers in marine geothermal environments are thermophilic and halotolerant. However, no one has surveyed an environment specifically for thermophilic bacteria that produce H(2) through Fe-Fe hydrogenases (H(2)ase). Using heterotrophic medium, several microflora from a seaweed bed associated with marine hot springs were enriched and analyzed for H(2) production. A H(2)-producing microflora was obtained from Sargassum sp., 16S rRNA genes and Fe-Fe H(2)ase diversities of this enrichment were also analyzed. Based on 16S rRNA genes analysis, 10 phylotypes were found in the H(2)-producing microflora showing 90.0-99.5 % identities to known species, and belonged to Clostridia, Gammaproteobacteria, and Bacillales. Clostridia were the most abundant group, and three Clostridia phylotypes were most related to known H(2) producers such as Anaerovorax odorimutans (94.0 % identity), Clostridium papyrosolvens (98.4 % identity), and Clostridium tepidiprofundi (93.1 % identity). For Fe-Fe H(2)ases, seven phylotypes were obtained, showing 63-97 % identities to known Fe-Fe H(2)ases, and fell into four distinct clusters. Phylotypes HW55-3 and HM55-1 belonged to thermophilic and salt-tolerant H(2)-producing Clostridia, Halothermothrix orenii-like Fe-Fe H(2)ases (80 % identity), and cellulolytic H(2)-producing Clostridia, C. papyrosolvens-like Fe-Fe H(2)ases (97 % identity), respectively. The results of both 16S rRNA genes and Fe-Fe H(2)ases surveys suggested that the thermophilic and halotolerant H(2)-producing microflora in seaweed bed of hot spring area represented previously unknown H(2) producers, and have potential application for H(2) production.

Culturability and secondary metabolite diversity of extreme microbes: expanding contribution of deep sea and deep-sea vent microbes to natural product discovery

Microbes from extreme environments do not necessarily require extreme culture conditions. Perhaps the most extreme environments known, deep-sea hydrothermal vent sites, support an incredible array of archaea, bacteria, and fungi, many of which have now been cultured. Microbes cultured from extreme environments have not disappointed in the natural products arena; diverse bioactive secondary metabolites have been isolated from cultured extreme-tolerant microbes, extremophiles, and deep-sea microbes. The contribution of vent microbes to our arsenal of natural products will likely grow, given the culturability of vent microbes; their metabolic, physiologic, and phylogenetic diversity; numerous reports of bioactive natural products from microbes inhabiting high acid, high temperature, or high pressure environments; and the recent isolation of new chroman derivatives and siderophores from deep-sea hydrothermal vent bacteria.