Roseovarius conchicola sp. nov. and Aliiroseovarius conchicola sp. nov., isolated from the marine conch Reishia bronni

The intertidal zone is an area located between the marine environment and the terrestrial environment and is exposed to various stresses. To investigate the mutualistic relationship between hosts and symbiotic micro-organisms inhabiting the intertidal zone, strains 2305UL8-3T and 2305UL8-7T were isolated from Reishia bronni, a species living in the intertidal zone of Ulleungdo Island, South Korea. Both strains are Gram-stain-negative, catalase- and oxidase-positive and facultatively anaerobic. Strains 2305UL8-3T and 2305UL8-7T grow optimally at 30.0 °C and 28.0-30.0 °C, respectively, under conditions of pH 8.0 and 3.0 % (w/v) NaCl. They have Q-10 as the primary quinone, and their common main fatty acids are C16:0 and summed feature 8 (C18:1 ω7c and/or C18:1 ω6c). Additionally, their primary polar lipids include phosphatidylcholine and phosphatidylglycerol. The two novel strains have an arsenic reduction pathway that reduces the oxidation state of arsenic and are expected to influence environmental regulation processes through the catabolic sulphate reduction system. Based on these characteristics, they exhibit resistance potential to environmental stresses, specifically arsenic exposure in the intertidal zone, where arsenic contamination is often associated with pollution and tidal fluctuations. Analysing the 16S rRNA gene sequence similarity, strain 2305UL8-3T shared 96.60 % similarity with Roseovarius faecimaris MME-070T, while strain 2305UL8-7T showed 98.13 % similarity with Aliiroseovarius sediminilitoris M-M10T. Polyphasic analysis revealed that strains 2305UL8-3T and 2305UL8-7T should be identified as novel species within the genera Roseovarius and Aliiroseovarius, respectively. Therefore, Roseovarius conchicola sp. nov. with the type strain 2305UL8-3T (=KCTC 8475T=MCCC 1K09523T=JCM 37202T) and Aliiroseovarius conchicola sp. nov. with the type strain 2305UL8-7T (=KCTC 8476T=MCCC 1K09524T=JCM 37203T) are proposed.

Roseovarius pelagicus sp. nov., a facultatively anaerobic bacterium with potential for degrading polypropylene, isolated from Arctic seawater

A Gram-stain-negative, facultatively anaerobic, non-motile, rod-shaped bacterial strain, designated HL-MP18T, was isolated from Arctic seawater after a prolonged incubation employing polypropylene as the sole carbon source. Phylogenetic analyses of the 16S rRNA gene sequence revealed that strain HL-MP18T was affiliated to the genus Roseovarius with close relatives Roseovarius carneus LXJ103T (96.8 %) and Roseovarius litorisediminis KCTC 32327T (96.5 %). The complete genome sequence of strain HL-MP18T comprised a circular chromosome of 3.86 Mbp and two circular plasmids of 0.17 and 0.24 Mbp. Genomic comparisons based on average nucleotide identity and digital DNA-DNA hybridization showed that strain HL-MP18T was consistently discriminated from its closely related taxa in the genus Roseovarius. Strain HL-MP18T showed optimal growth at 25 °C, pH 7.0 and 2.5 % (w/v) sea salts. The major cellular fatty acids were C18 : 1  ω6c and/or C18 : 1  ω7c (49.6 %), C19 : 0 cyclo ω8c (13.5 %), and C16 : 0 (12.8 %). The major respiratory quinone was ubiquinone-10. The polar lipids consisted of phosphatidylcholine, phosphatidylglycerol, an unidentified aminolipid and three unidentified lipids. The genomic DNA G+C content of the strain was 59.2 mol%. The phylogenetic, genomic, phenotypic and chemotaxonomic results indicate that strain HL-MP18T is distinguishable from the recognized species of the genus Roseovarius. Therefore, we propose that strain HL-MP18T represents a novel species belonging to the genus Roseovarius, for which the name Roseovarius pelagicus sp. nov. is proposed. The type strain is HL-MP18T (=KCCM 90405T=JCM 35639T).

Roseovarius gahaiensis sp. nov., isolated from Gahai Saline Lake, PR China

A Gram-stain-negative, aerobic, non-motile and ovoid- to rod-shaped bacterial strain, designated GH877^T, was isolated from a water sample of Gahai saline lake in Qaidam Basin,PR China. The isolate grew at 5-45 °C, pH 6.0-9.0 (optima, 37 °C and pH 7.5) and with 0.5-20 % (w/v) NaCl (optimum, 2.0 %). The neighbour-joining phylogenetic tree of 16S rRNA gene sequences showed that strain GH877^T belonged to the genus Roseovarius, and had highest 16S rRNA gene sequence similarity of 97.7 % to Roseovarius pacificus 81-2^T, followed by Roseovarius halotolerans HJ50^T (97.5 %) and Roseovarius litoreus GSW-M15^T (96.8 %). Genome sequencing revealed a genome size of 3 378 519 bp and a G+C content of 59.8 mol %. Up-to-date bacterial core gene set analysis indicated that strain GH877^T represents one independent lineage with R. pacificus DSM29589^T. The average nucleotide identity values of GH877^T with R. pacificus 81-2^T and R. halotolerans HJ50^T are 80.7 and 77.3 %, respectively. In silico DNA-DNA hybridization values between strain GH877^T and R. pacificus 81-2^T and R. halotolerans HJ50^T are 23.2 and 20.0 %, respectively. Q-10 was the predominant respiratory quinone and summed feature 8 (C_{18  :  1} ω7c and/or C_{18  :  1} ω6c) and C_{16  :  0} were the major cellular fatty acids. The polar lipids of strain GH877^T consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and two unidentified phosphoglycolipids. Based on polyphasic taxonomic analysis, strain GH877^T is proposed to represent a novel species of the genus Roseovarius, for which the name Roseovarius gahaiensis sp. nov. is proposed. (type strain GH877^T=CGMCC 1.13971^T=KCTC 72576^T).

Roseovarius arcticus sp. nov., a bacterium isolated from Arctic marine sediment

An aerobic, Gram-stain-negative, motile, rod or long-rod-shaped bacterial isolate, strain MK6-18T, was isolated from a marine sediment sample from Kongsfjorden, Arctic. The bacterium grew optimally at 20 °C, pH 7.0 and in the presence of 1.0–2.0 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain MK6-18T belonged to the genus Roseovarius . Its closest phylogenetic neighbour was Roseovarius nanhaiticus NH52JT showing 96.97 % 16S rRNA gene sequence similarity. The genome of strain MK6-18T is 4.2 Mb long in size with a G+C content of 59.5 mol%. The average nucleotide identity value between the genomes of strain MK6-18T and Roseovarius nanhaiticus NH52JT, was 78.0 %. Similar to other species of the genus Roseovarius , strain MK6-18T had ubiquinone 10 as the predominant ubiquinone and C12 : 0, C16 : 0, summed feature 3 (C16 : 1ω7c/ω6c) and summed feature 8 (C18 : 1ω7c/ω6c) as the major fatty acids. The polar lipid pattern consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine; one unidentified polar lipid, one unidentified aminolipid and one unidentified lipid were also detected. This is the first time that a member of the genus Roseovarius has been isolated from the Arctic, which may promote the study of the distribution characteristics and environmental adaptability of this genus. On the basis of the data provided here, strain MK6-18T should be classed as representing a novel species of the genus Roseovarius , for which the name Roseovarius arcticus sp. nov. is proposed. The type strain is MK6-18T (=CCTCC AB 2018219T=KCTC 72187T).

Roseovarius spongiae sp. nov., a bacterium isolated from marine sponge

A taxonomic study was carried out on strain HN-E21^T, which was isolated from sponge collected from Yangpu Bay, Hainan, PR China. Cells of strain HN-E21^T were Gram-stain-negative, non-spore-forming, tumbling-motile, ovoid- to rod-shaped and pale-yellow-pigmented that could grow at 15-42 °C (optimum, 37 °C), at pH 6-11 (pH 7) and in 0-14 % (w/v) NaCl (2-3 %). This isolate was positive for oxidase and catalase, but negative for hydrolysis of aesculin and gelatin. The phylogenetic tree based on 16S rRNA gene sequences showed that strain HN-E21^T formed a clade with Pelagivirga sediminicola BH-SD19^T, Pontibaca methylaminivorans GRP21^T, Roseovarius antarcticus M-S13-148^T, Roseovarius aquimarinus CAU1059^T and Roseovarius nanhaiticus NH52J^T within the family Rhodobacteraceae. Strain HN-E21^T shared the highest similarity to Pelagivirga sediminicola BH-SD19^T (95.5 %), followed by Roseovarius lutimaris 112^T (95.3 %), Pelagicola litorisediminis D1-W8^T (95.2 %), Roseovarius gaetbuli YM-20^T (95.0 %) and Roseovarius marisflavi H50^T (95.0 %). The dominant fatty acids were summed feature 8 (C_18 : 1ω7c and/or C_18 : 1ω6c) and C_16:0. The major polar lipids comprised phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, three unidentified lipids and one unidentified phospholipid. The respiratory quinone was identified as Q-10. The G+C content of the genomic DNA was 66.4 mol%. Based on the phenotypic and phylogenetic data, strain HN-E21^T represents a novel species of the genus Roseovarius, for which the name Roseovarius spongiae sp. nov. is proposed, with the type strain HN-E21^T (=MCCC 1K03333^T=LMG 30456^T).

Pelagivirga dicentrarchi sp. nov., a member of the family Rhodobacteraceae isolated from the gut microflora of sea bass (Dicentrarchus labrax L.)

A Gram-stain negative, aerobic, non-flagellated, non-gliding, rod-shaped bacterium, designated strain YLY04^T, was isolated from the gut microflora of a sea bass (Dicentrarchus labrax L.) collected from the coast of Yuanyao Wharf, Weihai, China. Growth was found to occur at pH 6.0-9.0 (optimum, 7.0-8.0), 4-37 °C (optimum, 28-30 °C) in the presence of 0-11.0% (w/v) NaCl (optimum, 3.0-4.0%). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain YLY04^T is closely related to Pelagivirga sediminicola BH-SD19^T and Roseovarius antarcticus M-S13-148^T. Strain YLY04^T contains ubiquinone-10 as the sole respiratory quinone and summed feature 8 (C_18:1ω7c and/or C_18:1ω6c), cyclo-C_19:0ω8c, C_16:0 and 11-methyl-C_18:1ω7c as the major fatty acids. The polar lipids of strain YLY04^T were found to consist of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, an unidentified aminolipid, an unidentified phospholipid and three unidentified lipids. The DNA G+C content was determined to be 62.7 mol%. The phenotypic, chemotaxonomic and phylogenetic properties, and genome analysis, indicated that strain YLY04^T represents a novel species within the genus Pelagivirga, for which the name Pelagivirga dicentrarchi sp. nov. is proposed. The type strain is YLY04^T (= MCCC 1H00334^T = KCTC 62452^T).

Roseovarius faecimaris sp. nov., isolated from a tidal flat

A Gram-stain-negative, obligate aerobic, non-motile and rod-shaped bacterium, designated MME-070^T, was isolated from a tidal flat near Muui-do, Incheon, Republic of Korea. This bacterium belonged to the Roseobacterclade within the family Rhodobacteraceae. The isolate grew at 20-40 °C, pH 7.0-9.0 with 1-5 % (w/v) NaCl. Optimal growth required 2-3 % (w/v) NaCl at 25-30 °C and pH 8.0. The 16S rRNA gene sequence of strain MME-070^T was most closely related to Roseovarius aestuarii SMK-122^T (96.9 %). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain MME-070^T clustered with the genus Roseovarius. The sole respiratory quinone was Q-10. Polar lipids were phosphatidylglycerol, phosphatidylcholine, diphosphatidylglycerol, unidentified aminolipid and some unidentified lipids. Major cellular fatty acids were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), 11-methyl C18 : 1ω7c and C16 : 0. The genomic DNA G+C content of the type strain was 63.6 mol%. Based on polyphasic taxonomic analysis, strain MME-070^T is proposed to represent a novel species of the genus Roseovarius, for which the name Roseovarius faecimaris sp. nov. is proposed. The type strain is MME-070^T (=KCCM 43142^T=JCM 30757^T).

Roseovarius ponticola sp. nov., a novel lipolytic bacterium of the family Rhodobacteraceae isolated from seawater

A lipolytic, Gram-negative, aerobic, non-motile and pleomorphic bacterial strain, designated W-SW3^T, was isolated from seawater around Wando, an island of South Korea, and its taxonomic position was determined using a polyphasic approach. Its optimal growth occurred at 30 °C, pH 7.0-8.0 and 2.0-4.0% (w/v) NaCl. Neighbour-joining phylogenetic tree of 16S rRNA gene sequences showed that strain W-SW3^T belonged to the genus Roseovarius of the family Rhodobacteraceae, by showing the highest 16S rRNA gene sequence similarity value (97.3%) to the type strain of Roseovarius nanhaiticus. Strain W-SW3^T exhibited 16S rRNA gene sequence similarities of 93.2-95.6% to the type strains of the other Roseovarius species. Ubiquinone-10 was found as the predominant ubiquinone and C_18:1ω7c and C_16:0 were found as the major fatty acids. Phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified lipid and one unidentified aminolipid were major polar lipids detected. The DNA G + C content of strain W-SW3^T was 63.9 mol%. Mean DNA-DNA relatedness values of strain W-SW3^T with the type strains of R. nanhaiticus and R. antarcticus were 18 and 9%, respectively. The phenotypic properties, together with the phylogenetic and genetic data, made it possible strain W-SW3^T to be separated from other recognized species of the genus Roseovarius. On the basis of the data presented, strain W-SW3^T represents a novel species of the genus Roseovarius, for which the name Roseovarius ponticola sp. nov. is proposed. The type strain is W-SW3^T (= KCTC 62424^T = KACC 19615^T = NBRC 113186^T).

Halophiles: biology, adaptation, and their role in decontamination of hypersaline environments

The unique cellular enzymatic machinery of halophilic microbes allows them to thrive in extreme saline environments. That these microorganisms can prosper in hypersaline environments has been correlated with the elevated acidic amino acid content in their proteins, which increase the negative protein surface potential. Because these microorganisms effectively use hydrocarbons as their sole carbon and energy sources, they may prove to be valuable bioremediation agents for the treatment of saline effluents and hypersaline waters contaminated with toxic compounds that are resistant to degradation. This review highlights the various strategies adopted by halophiles to compensate for their saline surroundings and includes descriptions of recent studies that have used these microorganisms for bioremediation of environments contaminated by petroleum hydrocarbons. The known halotolerant dehalogenase-producing microbes, their dehalogenation mechanisms, and how their proteins are stabilized is also reviewed. In view of their robustness in saline environments, efforts to document their full potential regarding remediation of contaminated hypersaline ecosystems merits further exploration.