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).

Marinifilum caeruleilacunae sp. nov., isolated from Yongle Blue Hole in the South China Sea

A Gram-stain-negative, non-motile, facultatively anaerobic and non-flagellated marine bacterium, designated JC070T was isolated from the Yongle Blue Hole in the South China Sea. The temperature, pH and NaCl ranges for growth of strain JC070T were 4–37 °C (optimum, 16 °C), pH 6.0–9.0 (optimum, pH 7.0) and 1.0 –6.0% (w/v; optimum, 3.0%). The predominant isoprenoid quinone of strain JC070T was identified as menaquinone-7. The dominant fatty acids (>10%) were iso-C15:0 (59.6%) and iso-C17:0 3-OH (17.2%). The major polar lipids were aminophospholipid, aminolipid, two unknown phospholipids and two unidentified lipids. The genomic DNA G+C content was determined to be 37.0 mol%. Based on the results of polyphasic analysis, a new species, named Marinifilum caeruleilacunae sp. nov., within the genus Marinifilum was proposed. The type strain is JC070T (= JCM 39045T=MCCC 1K03774T).

Host Traits and Phylogeny Contribute to Shaping Coral-Bacterial Symbioses

The success of tropical scleractinian corals depends on their ability to establish symbioses with microbial partners. Host phylogeny and traits are known to shape the coral microbiome, but to what extent they affect its composition remains unclear. Here, by using 12 coral species representing the complex and robust clades, we explored the influence of host phylogeny, skeletal architecture, and reproductive mode on the microbiome composition, and further investigated the structure of the tissue and skeleton bacterial communities. Our results show that host phylogeny and traits explained 14% of the tissue and 13% of the skeletal microbiome composition, providing evidence that these predictors contributed to shaping the holobiont in terms of presence and relative abundance of bacterial symbionts. Based on our data, we conclude that host phylogeny affects the presence of specific microbial lineages, reproductive mode predictably influences the microbiome composition, and skeletal architecture works like a filter that affects bacterial relative abundance. We show that the β-diversity of coral tissue and skeleton microbiomes differed, but we found that a large overlapping fraction of bacterial sequences were recovered from both anatomical compartments, supporting the hypothesis that the skeleton can function as a microbial reservoir. Additionally, our analysis of the microbiome structure shows that 99.6% of tissue and 99.7% of skeletal amplicon sequence variants (ASVs) were not consistently present in at least 30% of the samples, suggesting that the coral tissue and skeleton are dominated by rare bacteria. Together, these results provide novel insights into the processes driving coral-bacterial symbioses, along with an improved understanding of the scleractinian microbiome.

Microorganisms from deep-sea hydrothermal vents

With a rich variety of chemical energy sources and steep physical and chemical gradients, hydrothermal vent systems offer a range of habitats to support microbial life. Cultivation-dependent and independent studies have led to an emerging view that diverse microorganisms in deep-sea hydrothermal vents live their chemolithoautotrophic, heterotrophic, or mixotrophic life with versatile metabolic strategies. Biogeochemical processes are mediated by microorganisms, and notably, processes involving or coupling the carbon, sulfur, hydrogen, nitrogen, and metal cycles in these unique ecosystems. Here, we review the taxonomic and physiological diversity of microbial prokaryotic life from cosmopolitan to endemic taxa and emphasize their significant roles in the biogeochemical processes in deep-sea hydrothermal vents. According to the physiology of the targeted taxa and their needs inferred from meta-omics data, the media for selective cultivation can be designed with a wide range of physicochemical conditions such as temperature, pH, hydrostatic pressure, electron donors and acceptors, carbon sources, nitrogen sources, and growth factors. The application of novel cultivation techniques with real-time monitoring of microbial diversity and metabolic substrates and products are also recommended.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-020-00086-4.

Characterization of Peptacetobacter hominis gen. nov., sp. nov., isolated from human faeces, and proposal for the reclassification of Clostridium hiranonis within the genus Peptacetobacter

A novel, Gram-stain-positive, rod-shaped, non-motile, non-spore-forming, obligately anaerobic bacterium, designated strain ZHW00191^T, was isolated from human faeces and characterized by using a polyphasic taxonomic approach. Growth occurred at 25-45 °C (optimum, 37-42 °C), at pH 5.5-10.0 (optimum, pH 6.5-7.0) and with 0-2 % (w/v) NaCl (optimum, 0 %). The end products of glucose fermentation were acetic acid, isobutyric acid and isovaleric acid and a small amount of propionic acid. The dominant cellular fatty acids (>10 %) of strain ZHW00191^T were C_16 : 0, C_18 : 1 ω9с and C_18 : 2ω6,9с. Its polar lipid profile comprised diphosphatidylglycerol, phosphatidylglycerol, three unidentified phospholipids and ten unidentified glycolipids. Respiratory quinones were not detected. The cell-wall peptidoglycan contained meso-2,6-diaminopimelic acid, and the whole-cell sugars were ribose and glucose. The genomic DNA G+C content was 32.8 mol%. Analysis of the 16S rRNA gene sequence indicated that ZHW00191^T was most closely related to Clostridium hiranonis TO-931^T (95.3 % similarity). Average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) analyses with closely related reference strains indicated that reassociation values were both well below the thresholds of 95-96% and 70 % for species delineation, respectively. Based on phenotypic, chemotaxonomic and genetic studies, a novel genus, Peptacetobacter gen. nov., is proposed. The novel isolate ZHW00191^T (=JCM 33482^T=GDMCC 1.1530^T) is proposed as the type strain of the type species Peptacetobacter hominis gen. nov., sp. nov. of the proposed new genus. Furthermore, it is proposed that Clostridium hiranonis be transferred to this novel genus, as Peptacetobacter hiranonis comb. nov.

Novel clostridial lineages recovered from metagenomes of a hot oil reservoir

Oil reservoirs have been shown to house numerous microbial lineages that differ based on the in-situ pH, salinity and temperature of the subsurface environment. Lineages of Firmicutes, including Clostridiales, have been frequently detected in oil reservoirs, but are typically not considered impactful or relevant due to their spore-forming nature. Here we show, using metagenomics, a high temperature oil reservoir of marine salinity contains a microbial population that is predominantly from within the Order Clostridiales. These organisms form an oil-reservoir specific clade based on the phylogenies of both 16S rRNA genes and ribosomal proteins, which we propose to name ^UPetromonas tenebris, meaning they are single-celled organisms from dark rocks. Metagenome-assembled genomes (MAGs) of these Petromonas sp. were obtained and used to determine that these populations, while capable of spore-formation, were also likely replicating in situ in the reservoir. We compared these MAGs to closely related genomes and show that these subsurface Clostridiales differ, from the surface derived genomes, showing signatures of the ability to degrade plant-related compounds, whereas subsurface genomes only show the ability to process simple sugars. The estimation of in-situ replication from genomic data suggest that ^UPetromonas tenebris lineages are functional in-situ and may be specifically adapted to inhabit oil reservoirs.

Puteibacter caeruleilacunae gen. nov., sp. nov., a facultatively anaerobic bacterium isolated from Yongle Blue Hole in the South China Sea

Blue holes are unique geomorphological units characterized by steep redox and biogeochemical gradients. Yongle Blue Hole is located on the largest atoll (Yongle Atoll) of the western Xisha Islands in the South China Sea. A Gram-stain-negative, facultatively anaerobic, non-motile, non-flagellated marine bacterium with creamy white colonies, designated JC036T, was isolated from Yongle Blue Hole. Cells were short-rod-shaped and catalase-negative. 16S rRNA gene sequence analysis showed that sequence similarities were lower than 91.6 % against all validly named species in the familyProlixibacteraceae; a reconstructed phylogenetic tree indicated that strain JC036Tformed a lineage with strains in the familyProlixibacteraceae. Growth occurred at 4–37 °C (optimum, 28 °C), at pH 5.0–9.0 (optimum, 7.0) and in the presence of 2–6 % (w/v) NaCl (optimum, 3 %). The prevalent isoprenoid quinone of strain JC036Twas menaquinone-7 (MK-7). Iso-C15 : 0and iso-C17 : 03-OH were the predominant fatty acids. The major polar lipids included a phospholipid, phosphatidylethanolamine, an aminophospholipid and four unidentified lipids. The genomic DNA G+C content of strain JC036Twas 37.8 mol%. Based on physiological and biochemical characteristics and whole genome comparisons, we propose a new genus and species,Puteibacter caeruleilacunaegen. nov., sp. nov., within the familyProlixibacteraceae. The type strain ofPuteibacter caeruleilacunaeis JC036T(=JCM 33128T=MCCC 1K03579T). From this study, a deeper understanding of the community of the microorganism and their roles in biogeochemical cycles, especially anaerobic bacteria, is provided.

Ancylomarina longa sp. nov., isolated from southern Okinawa Trough sediment and emended description of the family Marinifilaceae

A Gram-stain-negative, obligately anaerobic, non-motile, non-spore-forming, long-rod-shaped and non-flagellated bacterial strain, designated T3-2 S1-C^T, was isolated from a sediment sample collected at the Okinawa Trough. Phylogenetic analyses of 16S rRNA gene sequences and the whole genome revealed that strain T3-2 S1-C^T was a member of the family Marinifilaceae and exhibited less than 95.1 % sequence similarities to the closely related type strains of the family Marinifilaceae. Optimal growth occurred at pH 7.0, 28 °C and in the presence of 3 % (w/v) NaCl. The isoprenoid quinone of strain T3-2 S1-C^T was identified as menaquinone-7 (MK-7) and the predominant fatty acids (>10 %) were iso-C_{15 : 0} (38.9 %) and anteiso-C_{15 : 0} (11.6 %). The major polar lipids were one phosphatidylethanolamine, one phosphatidylmonomethylethanolamine, one aminolipids, two unidentified lipids and two unidentified phospholipids. The DNA G+C content of strain T3-2 S1-C^T was 35.7 mol%. On the basis of the results of polyphasic analyses, strain T3-2 S1-C^T is considered to represent a novel species of the genus Ancylomarina, for which the name Ancylomarina longa sp. nov. is proposed. The type strain is T3-2 S1-C^T (=KCTC 15505^T=MCCC 1K01617^T).

Marinifilum breve sp. nov., a marine bacterium isolated from the Yongle Blue Hole in the South China Sea and emended description of the genus Marinifilum

A Gram-stain-negative, facultative anaerobic, non-motile, short-clavate and non-flagellated marine bacterium strain, designated JC075^T, was isolated from the Yongle Blue Hole in the South China Sea. Based on the 16S rRNA gene sequence, strain JC075^T was found to be closely related to Marinifilum albidiflavum FB208^T (97.10 %), Marinifilum flexuosum DSM 21950^T (96.43 %) and Marinifilum fragile JCM 15579^T (95.58 %), with less than 90.24 % sequence similarity to other genera of the family Marinifilaceae. The growth temperature was in the range of 10-37 °C, and the optimum temperature was 16 °C. Optimal growth occurred at pH 7.0 and in the presence of 3 % (w/v) NaCl. The isoprenoid quinone of strain JC075^T was identified as menaquinone-7 and the predominant fatty acids (>10 %) were iso-C15 : 0 (47.9 %), summed feature 9 (C17 : 1 or/and iso-C17 : 1ω9c; 18.7 %) and iso-C17 : 0 3-OH (14.9 %). The major polar lipids were one phosphatidylethanolamine, one phospholipid, one aminophospholipid, one glycolipid, one aminolipid and two unidentified lipids. The DNA G+C content of strain JC075^T was 35.8 mol%. On the basis of polyphasic analysis, strain JC075^T was considered to represent a novel species of the genus Marinifilum, for which the name Marinifilumbreve sp. nov. is proposed. The type strain is JC075^T (=KCTC 15646^T=MCCC 1K03477^T=JCM 32401^T).

Draft Genome Sequence of Anaerobic Fermentative Bacterium Anaeromicrobium sediminis DY2726D

Here, we report the draft genome sequence of Anaeromicrobium sediminis DY2726D, isolated from a west Pacific Ocean sediment sample. The genome comprises 4,710,590 bp in 56 contigs, with a G+C content of 31.2%. A total of 3,811 protein-coding sequences were predicted. The genome annotation revealed that DY2726D may represent a marine type of Clostridiaceae.

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).