Marinobacter mangrovi sp. nov., isolated from mangrove sediment.

A novel marine bacterium, designated strain CHFG3-1-5T, was isolated from mangrove sediment sampled at Jiulong River estuary, Fujian, PR China. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain CHFG3-1-5T belonged to the genus Marinobacter, with the highest sequence similarity to Marinobacter segnicrescens SS011B1-4T (97.6%), followed by Marinobacter nanhaiticus D15-8WT (97.5%), Marinobacter bohaiensis T17T (97.1%) and Marinobacter hydrocarbonoclasticus SP.17T (90.6%). The bacterium was Gram-stain-negative, facultative anaerobic, oxidase- and catalase-positive, rod-shaped and motile with a polar flagellum. Strain CHFG3-1-5T grew optimally at 32-37 °C, pH 6.0-8.0 and in the presence of 2.0-3.0% (w/v) NaCl. The G+C content of the chromosomal DNA was 61.1 mol%. The major respiratory quinone was determined to be Q-9. The principal fatty acids were C16 : 0, summed feature 3 (C16 : 1 ω7c/ω6c), C12 : 0, summed feature 9 (C17 : 1 iso ω9c and/or C16 : 0 10-methyl), C12 : 0 3-OH and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c). The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, three phospholipids, one glycolipid and two aminolipids. The average nucleotide identity and digital DNA-DNA hybridization values among the genomes of strain CHFG3-1-5T and the reference strains were 73.4-79.4 and 19.6-22.4%, respectively. Like many other species reported in the genus Marinobacter, strain CHFG3-1-5T was able to oxidise iron. The combined genotypic and phenotypic data showed that strain CHFG3-1-5T represents a novel species within the genus Marinobacter, for which the name Marinobacter mangrovi sp. nov. is proposed, with the type strain CHFG3-1-5T (=MCCC 1A18306T=KCTC 82398T).

Marinobacter halodurans sp. nov., a halophilic bacterium isolated from sediment of a salt flat.

A Gram-staining-negative, aerobic, cream-coloured, marine bacterium, with rod-shaped cells, designated strain YJ-S3-2T, was isolated from salt flat sediment of Yongyu-do, Republic of Korea. YJ-S3-2T grew at pH 5.0-9.0 (optimum pH 7.0), 4-45 °C (optimum 30 °C) and with 1-18 % (w/v) NaCl (optimum 6 %). The results of 16S rRNA gene sequence analysis indicated that YJ-S3-2T was closely related to Marinobacter segnicrescens SS011B1-4T (97.0 %) followed by, 'Marinobacter nanhaiticus' D15-8W (96.7 %), Marinobacter bryozoorum 50-11T (96.7 %), Marinobacter koreensis DSMZ 179240T T (96.5 %) and Marinobacter bohaiensis T17T (96.5 %). The average nucleotide identity (ANI) and the genome to genome distance calculator (GGDC) estimate values between YJ-S3-2T and related type strains were 73.7-79.8 and 19.9-22.5 %, and also 73.5 and 20.7 % with Marinobacter hydrocarbonoclasticus. YJ-S3-2T was characterized as having Q-9 as the predominant respiratory quinone and the principal fatty acids (>10 %) were C16 : 0 (22.3 %), summed feature 9 (C17 : 1iso ω9c/C16 : 0 10-methyl, 13.8 %) and 3 (C16 : 1ω7c/C16 : 1ω6c, 11.9 %). The polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, two unidentified aminolipids and two unidentified phospholipids. The DNA G+C content of YJ-S3-2T is 60.9 mol%. On the basis of the polyphasic taxonomic evidence presented in this study, YJ-S3-2T should be classified as representing a novel species within the genus Marinobacter, for which name Marinobacter halodurans sp. nov. is proposed, with the type strain YJ-S3-2T (=KACC 19883T=KCTC 62937T=JCM 33109T).

Aerobic degradation of cis-dichloroethene by the marine bacterium Marinobacter salsuginis strain 5N-3.

An aerobic bacterium, designated strain 5N-3 (NBRC 113055), that degrades cis-dichloroethene (cDCE) was isolated from a sea sediment in Japan. Strain 5N-3 was able to degrade a certain amount of cDCE in the presence of pyruvate without the action of inducers. In the presence of inducers, such as phenol and benzene, the strain completely removed cDCE. By the application of 16S ribosomal RNA (16S rRNA) gene sequencing and average nucleotide identity analyses, the strain 5N-3 was identified as Marinobacter salsuginis. On the other hand, identified species of Marinobacter are not known to degrade cDCE at all. A draft genome sequence analysis of the strain 5N-3 suggested that the dmp-homologous operon (operon for phenol degradation) may be contributing to the aerobic degradation of cDCE. This is the first report on an aerobic marine bacterium that has been found to degrade cDCE.

Marinobacter salinexigens sp. nov., a marine bacterium isolated from hadal seawater of the Mariana Trench.

A Gram-stain-negative, strictly aerobic, non-motile and rod-shaped bacterium, designated ZYF650T, was isolated from the hadal seawater (9600 m) of the Mariana Trench. Results of phylogenetic analysis based on 16S rRNA gene sequences indicated that ZYF650T formed a lineage within the family Alteromonadaceae that was distinct from the most closely related species Marinobacter mobilis and Marinobacter nitratireducens with 16S rRNA gene sequences similarities of 98.0 and 97.7 %, respectively. Strain ZYF650T showed average nucleotide identity values of 75.7 % with Marinobacter hydrocarbonoclasticus, 73.3 % with Marinobacter mobilis and 79.3 % with Marinobacter nitratireducens, and DNA-DNAhybridization values of 21.5, 21.3 and 22.0 % with M. hydrocarbonoclasticus, M. mobilis and M. nitratireducens, respectively, which were lower than the threshold for species delineation. Strain ZYF650T grew with 0-14 % (w/v) NaCl (optimum, 7-8 %) at a temperature range of 10-45 °C (optimum, 28 °C) and pH 6.0-9.5 (optimum, pH 7.0-8.0). The sole respiratory quinone was ubiquinone-9 (Q-9). The polar lipids in ZYF650T comprised phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, three unidentified polar lipids, two unidentified aminolipids and two phospholipids. The predominant fatty acids (more than 10 % of total fatty acids) were C18 : 1 ω9c (21.9 %), C16 : 0 (21.7 %), C12 : 0 3-OH (14.0 %), C16 : 1 ω9c (13.2 %) and C12 : 0 (12.2 %). The DNA G+C content of strain ZYF650T was 55.6 %. On the basis of polyphasic taxonomic analysis, strain ZY650T is considered to represent a novel specie of the genus Marinobacter in the family Alteromonadaceae, for which the name Marinobacter salinexigens sp. nov. is proposed. The type strain is ZYF650T (=JCM 33013T=MCCC 1K03552T).

Marinobacter changyiensis, sp. nov., isolated from offshore sediment.

An aerobic, Gram-stain-negative bacterium, designated CLL7-20T, was isolated from a marine sediment sample from offshore of Changyi, Shandong Province, China. Cells of strain CLL7-20T were rod-shaped, motile with one or more polar flagella, and grew optimally at pH 7.0, at 28 °C and with 3 % (w/v) NaCl. The principal fatty acids of strain CLL7-20T were C16 : 0 and summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c). The main polar lipids of strain CLL7-20T were phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG) and an unidentified aminolipid (AL). Strain CLL7-20T contained Q-9 as the major respiratory quinone. The G+C content of its genomic DNA was 56.2 mol%. Phylogenetically, strain CLL7-20T branched within the genus Marinobacter, with M. daqiaonensis YCSA40T being its closest phylogenetic relative (96.7 % 16S rRNA gene sequence similarity), followed by M. sediminum R65T (96.6 %). Average nucleotide identity and in silico DNA-DNA hybridization values between strain CLL7-20T and the closest related reference strains were 73.2% and 19.8 %, respectively. On the basis of its phenotypic, phylogenetic and chemotaxonomic characteristics, we suggest that strain CLL7-20T (=MCCC 1A14855T=KCTC 72664T) is the type strain of a novel species in the genus Marinobacter, for which the name Marinobacter changyiensis sp. nov. is proposed. Based on the genomic analysis, siderophore genes were found from strain CLL7-20T, which indicate its potential as a promising alternative to chemical fertilizers in iron-limitated environments such as saline soils.

Marinobacter denitrificans sp. nov., isolated from marine sediment of southern Scott Coast, Antarctica.

A novel bacterium, designated JB02H27T, was isolated from marine sediment collected from the southern Scott Coast, Antarctica. Cells were Gram-stain-negative, facultatively anaerobic, polar-flagellated and motile rods. Growth occurred at 4-45 °C, at pH 7.0-9.0 and with 3-25 % (w/v) NaCl. Phylogenetic trees based on 16S rRNA gene sequences showed that strain JB02H27T consistently fell within the genus Marinobacter and formed a clade together with Marinobacter algicola DG893T (98.8 % similarity), Marinobacter confluentis KCTC 42705T (98.4 %), Marinobacter salarius R9SW1T (98.4%) and Marinobacter halotolerans CP12T (97.9 %), which were subsequently used as reference strains for comparisons of phenotypic and chemotaxonomic characteristics. Average nucleotide identity values between strain JB02H27T and the four related type strains were 80.9, 76.6, 81.9 and 76.3 %, respectively. The major fatty acids were summed feature 3, C16 : 0, C18 : 1 ω9c and C16 : 0 N alcohol. The polar lipids included phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, and an unidentified phospholipid, aminolipid, aminophospholipid and glycolipids. The sole respiratory quinone was ubiquinone-9. The DNA G+C content was 56.9 mol%. Based on the genomic, phylogenetic, phenotypic and chemotaxonomic analysis, we propose that strain JB02H27T represents a novel species of the genus Marinobacter, for which the name Marinobacter denitrificans sp. nov. is proposed. The type strain is JB02H27T (=GDMCC 1.1528T=KCTC 62941T).

Marinobacter vulgaris sp. nov., a moderately halophilic bacterium isolated from a marine solar saltern.

A facultatively anaerobic, Gram-stain-negative and non-gliding bacterium, designated F01T, was isolated from marine solar saltern in Weihai, PR China. Cells of F01T were 0.2-0.4 µm wide and 1.4-4.1 µm long, weakly catalase-positive and oxidase-negative. Growth of F01T was determined to occur at 4-40 °C (optimum, 33-37 °C), pH 6.5-8.5 (optimum, 7.0-8.0), and with 0.5-18.0 % (w/v) NaCl (optimum, 3.0-6.0 %). The 16S rRNA gene sequence analysis indicated that F01T represented a member of the genus Marinobacter within the family Alteromonadaceae. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the isolate was most closely related to Marinobacter algicola DSM 16394T, with a sequence similarity of 97.5 %. The DNA G+C content of the isolate was 57.6 mol%. The major respiratory quinone of F01T was ubiquinone-9 (Q-9) and the major fatty acids were anteiso-C15 : 0, C16 : 0 and C18 : 1ω9c. The major polar lipids were phosphoaminolipid, phosphatidylglycerol and phosphatidylethanolamine. On the basis of the results of the phylogenetic analysis and phenotypic properties, it is concluded that F01T can be considered to represent a novel species in the genus Marinobacter, for which the name Marinobacter vulgaris sp. nov. is proposed. The type strain is F01T (=MCCC 1H00290T=KCTC 52700T).

Marinobacter nauticus (Baumann et al. 1972) comb. nov. arising from instances of synonymy and the incorrect interpretation of the International Code of Nomenclature of Prokaryotes.

Studies on Pseudomonas nautica Baumann et al. 1972 (Approved Lists 1980) and Marinobacter hydrocarbonoclasticus Gauthier et al. 1992 have shown that they should be treated as heterotypic synonyms. As a consequence, they have been treated as belonging to a single species, Marinobacter hydrocarbonoclasticus Gauthier et al. 1992. This interpretation of the International Code of Nomenclature of Bacteria/Prokaryotes is, however, based on a fundamental flaw in the interpretation of the wording of Rule 15 as documented in the 1975 and 1990 revisions where the wording has been partially corrected in the 2008 revision. A key aspect of the incorrect interpretation is that the nomenclatural type of a taxon, in this case Marinobacter hydrocarbonoclasticus Gauthier et al. 1992 (the nomenclatural type of the Marinobacter Gauthier et al. 1992) must be used instead of recognising the priority of the epithet in Pseudomonas nautica Baumann et al. 1972 (Approved Lists 1980), with the creation of a new combination Marinobacter nauticus (Baumann et al. 1972). It is now clear that there is no justification for that interpretation and it is necessary to create a new combination, Marinobacter nauticus (Baumann et al. 1972) in the situation where Marinobacter hydrocarbonoclasticus Gauthier et al. 1992 and Pseudomonas nautica Baumann et al. 1972 (Approved Lists 1980) are treated as heterotypic synonyms. Additional studies have shown that Marinobacter aquaeolei Nguyen et al. 1993 and Marinobacter hydrocarbonoclasticus Gauthier et al. 1992 should also be treated as heterotypic synonyms.

Marinobacter fonticola sp. nov., isolated from deep sea cold seep sediment.

In this study, we report a novel Gram-negative bacterium, designated as strain CS412T, isolated from deep-sea sediment collected in a cold seep area of the South China Sea. Growth of strain CS412T occurred at 4-40 °C (optimum, 28 °C), pH 5.0-11.0 (optimum, pH 6.0) and with 0-19 % (w/v) NaCl (optimum, 1-2 %). Phylogenetic analysis based on 16S rRNA gene sequence data indicated that strain CS412T belonged to the genus Marinobacter. The closest phylogenetic neighbours of strain CS412T were Marinobacter pelagius HS225T (96.9 %), Marinobacter szutsaonensis NTU-104T (96.8%), Marinobacter santoriniensis NKSG1T (96.4%) and Marinobacter koreensisdd-M3T (96.3 %). The genomic DNA G+C content of strain CS412T was 58.0 mol%. The principal respiratory quinone was ubiquinone-9 (Q-9). The polar lipids of CS412T contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, aminophospholipidand and four glycolipids. The major fatty acids of CS412T contained cyclo-C19 : 0ω8c, C16 : 0, C18 : 1ω7c and C18 : 1ω7c 11-methyl. The results of phylogenetic, physiological, biochemical and morphological analyses suggested that strain CS412T represents a novel species of the genus Marinobacter, and the name Marinobacter fonticola sp. nov. is proposed with the type species CS412T (=CCTCC AB 2019197T=KCTC 72475T).

Marinobacter maroccanus sp. nov., a moderately halophilic bacterium isolated from a saline soil.

During the taxonomic investigation of exopolymer-producing halophilic bacteria, a rod-shaped, motile, Gram-stain-negative, halophilic bacterium, designated strain N4T, was isolated from a saline soil located in northern Morocco. Optimal growth of the isolate was at 30-37 ºC and at pH 7.0-8.0, in the presence of 5-7 % (w/v) NaCl. Useful characteristics for the phenotypic differentiation of strain N4T from other Marinobacter species included α-chymotrypsin and α-glucosidase activities and the carbohydrate assimilation profile. The major fatty acids detected in strain N4T were C16:0 and C18:1ω9c and the predominant respiratory quinone was ubiquinone-9. Sequence analysis of the 16S rRNA gene indicated that strain N4T belonged to the genus Marinobacter and was closely related to the type strains of Marinobacter adhaerens (99.04 % similarity), Marinobacter salsuginis (98.97 %) and Marinobacter flavimaris (98.36 %). Phylogenetic analysis of the rpoD gene sequence also showed that the nearest neighbours of strain N4T were M. salsuginis (91.49 % similarity), M. adhaerens and M. flavimaris (90.63 %). Strain N4T showed 87.98 % average nucleotide identity with M. flavimaris and M. salsuginis, and 87.47 % with M. adhaerens. Regarding in-silico genome-to-genome distance, strain N4T showed DNA-DNA hybridization values of 33.30 % with M. adhaerens, 34.60 % with M. flavimaris and 34.70 % with M. salsuginis. The DNA G+C content of strain N4T was 57.3 mol%. Based on the results of phenotypic characterization, phylogenetic analysis and genome comparison, strain N4T represents a novel species of the genus Marinobacter, for which the name Marinobacter maroccanus sp. nov. is proposed. The type strain is N4T (=CECT 9525T=LMG 30466T).

Marinobacter profundi sp. nov., a slightly halophilic bacterium isolated from a deep-sea sediment sample of the New Britain Trench.

A piezotolerant, cold-adapted, slightly halophilic bacterium, designated strain PWS21T, was isolated from a deep-sea sediment sample collected from the New Britain Trench. Cells were observed to be Gram-stain negative, rod-shaped, oxidase- and catalase-positive. Growth of the strain was observed at 4-45 °C (optimum 37 °C), at pH 5.0-9.0 (optimum 7.0) and in 0.5-20% (w/v) NaCl (optimum 3-4%). The optimum pressure for growth was 0.1 MPa (megapascal) with tolerance up to 70 MPa. 16S rRNA gene sequence analysis showed that strain PWS21T is closely related to Marinobacter guineae M3BT (98.4%) and Marinobacter lipolyticus SM19T (98.2%). Multilocus sequence analysis (MLSA) based on sequences of housekeeping genes gyrB, recA, atpD, rpoB and rpoD indicates that strain PWS21T represents a distinct evolutionary lineage within the genus Marinobacter. Furthermore, strain PWS21T showed low ANI and diDDH values to the closely related species. The principal fatty acids were identified as C12:0, C12:0 3-OH, C16:1ω9c, C16:0 and C18:1ω9c. Ubiquinone-9 was identified as the major respiratory quinone. The polar lipids were identified as phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), aminophospholipid (APL), two unidentified lipids and an unidentified phospholipid (PL). The G + C content of the genomic DNA was determined to be 60.3 mol%. On the basis of phenotypic, chemotaxonomic and molecular data, we conclude that strain PWS21T represents a novel species of the genus Marinobacter, for which the name Marinobacter profundi sp. nov. is proposed (type strain PWS21T = KCTC 52990T = MCCC 1K03345T).

Marinobacter bohaiensis sp. nov., a moderate halophile isolated from benthic sediment of the Bohai Sea.

A Gram-stain-negative, motile, aerobic and rod-shaped bacterial strain, designated T17T, was isolated from benthic sediment sampled at Jiaozhou Bay, Bohai Sea, China, and its taxonomic position was investigated. The 16S rRNA gene sequence of strain T17T exhibited the highest similarity values to those of the type strain Marinobacter lacisalsi FP2.5 (96.2 %) and Marinobacter koreensis DD-M3T (96.2 %). Strain T17T grew optimally at 35 °C, pH 7.0-8.0 and in the presence of 6.0-10.0 % (w/v) NaCl. The predominant ubiquinone in strain T17T was identified as Q-9. The major fatty acids of strain T17T were C12 : 0, C16 : 0 and C16 : 0 10-CH3. The major polar lipids of strain T17T were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidglycerol, an unidentified aminolipid and an unidentified phospholipid. The DNA G+C content of strain T17T was 63.0 mol%. The draft genome sequence of strain T17T includes 4 755 891 bp in total (N50=2 856 325 bp) with a medium read coverage of 100.0x and 11 scaffolds. In silico DNA-DNA hybridization with the three type strains showed 20.3, 19.7 and 19.9 % relatedness to Marinobacter santoriniensis NKSG1T, Marinobacter segnicrescens SS11B1-4T and Marinobacter daqiaonensis CGMCC 1.9167T, respectively. On the basis of the phenotypic, phylogenetic, genomic and chemotaxonomic properties, strain T17T is considered to represent a novel species within the genus Marinobacter, for which the name Marinobacterbohaiensis sp. nov. is proposed. The type strain is T17T (=KCTC 52710T=MCCC 1K03282T).

Marinobacter fuscus sp. nov., a marine bacterium of Gammaproteobacteria isolated from surface seawater.

A Gram-stain-negative bacterium, designated NH169-3T, was isolated from a surface seawater sample of the South China Sea and subjected to a taxonomic polyphasic investigation. Strain NH169-3T was strictly aerobic, non-motile, non-spore-forming and rod-shaped. The colony was 1.0-2.0 mm in diameter after the growth on marine agar at 30 °C for 72 h. The centre of the colony was smooth, circular, convex and brown with a transparent periphery. Strain NH169-3T was able to grow at temperatures between 4-40 °C (optimum, 37 °C), pH 5.5-9.0 (pH 7.5) and with 0-12.5 % (w/v) NaCl (3.0 %). Chemotaxonomic analysis showed that the sole respiratory quinone of strain NH169-3T was ubiquinone 9; major fatty acids were C16 : 0 and C18 : 1ω9c, and major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and one unidentified glycolipid. The DNA G+C content was 52.7 mol%. The comparison of 16S rRNA gene sequences showed that strain NH169-3T was closely related to Marinobacter shengliensis SL013A34A2T with a similarity of 98.0 %. Three phylogenetic trees reconstructed with neighbour-joining, maximum-parsimony and maximum-likelihood methods using 16S rRNA gene sequences showed that strain NH169-3T was grouped into a separated branch with M. shengliensis SL013A34A2T in a clade of the genus Marinobacter and closely related to Marinobacter halophilus JCM 30472T, Marinobacter vinifirmus DSM 17747T and Marinobacter hydrocarbonoclasticus DSM 8798T. Analyses of both phenotypic and phylogenetic properties have suggested that strain NH169-3T was distinctive from species with validly published names in genus Marinobacter. Thus, strain NH169-3T (=MCCC 1K03455T=KCTC 62226T) is proposed as a novel species in genus Marinobacter with the name Marinobacter fuscus sp. nov.

AupA and AupB Are Outer and Inner Membrane Proteins Involved in Alkane Uptake in Marinobacter hydrocarbonoclasticus SP17.

This study describes the functional characterization of two proteins, AupA and AupB, which are required for growth on alkanes in the marine hydrocarbonoclastic bacterium Marinobacter hydrocarbonoclasticus The aupA and aupB genes form an operon whose expression was increased upon adhesion to and biofilm formation on n-hexadecane. AupA and AupB are outer and inner membrane proteins, respectively, which are able to interact physically. Mutations in aupA or/and aupB reduced growth on solid paraffin and liquid n-hexadecane, while growth on nonalkane substrates was not affected. In contrast, growth of aup mutants on n-hexadecane solubilized in Brij 58 micelles was completely abolished. Mutant cells had also lost the ability to bind to n-hexadecane solubilized in Brij 58 micelles. These results support the involvement of AupA and AupB in the uptake of micelle-solubilized alkanes and provide the first evidence for a cellular process involved in the micellar uptake pathway. The phylogenetic distribution of the aupAB operon revealed that it is widespread in marine hydrocarbonoclastic bacteria of the orders Oceanospirillales and Alteromonadales and that it is present in high copy number (up to six) in some Alcanivorax strains. These features suggest that Aup proteins probably confer a selective advantage in alkane-contaminated seawater.IMPORTANCE Bacteria are the main actors of the biological removal of hydrocarbons in seawater, and so, it is important to understand how they degrade hydrocarbons and thereby mitigate marine environmental damage. Despite a considerable amount of literature about the dynamic of microbial communities subjected to hydrocarbon exposure and the isolation of strains that degrade hydrocarbons, most of the genetic determinants and molecular mechanisms of bacterial hydrocarbon uptake remain unknown. This study identifies two genes, aupA and aupB, in the hydrocarbonoclastic bacterium Marinobacter hydrocarbonoclasticus that are present frequently in multiple copies in most of the marine hydrocarbon-degrading bacteria for which the genomic sequence is available. AupA and AupB are two novel membrane proteins interacting together that are involved in the uptake of alkanes dissolved in surfactant micelles. The function and the phylogenetic distribution of aupA and aupB suggest that they might be one attribute of the remarkable adaptation of marine hydrocarbonoclastic bacteria that allow them to take advantage of hydrocarbons.

Changes in morphology and metabolism enable Mn-oxidizing bacteria from mid-oceanic ridge environment to counter metal-induced stress.

Mn-oxidizing potential of two metal-tolerant bacterial strains - Halomonas meridiana and Marinobacter algicola isolated from the South West Indian Ridge waters were compared at varying concentrations of Mn (II), i.e., 1, 10, and 100 µmol and mmol L-1 . Accompanying changes in their morphology and metabolism were also determined. At concentrations >1 mmol L-1 Mn (II), Mn-oxidizing potential of M. algicola was 2-7 times greater than that of H. meridiana. Scanning electron microscopy revealed that exposure to elevated metal content prompted bacterial cells especially those of M. algicola to been enveloped in exopolymeric material and form aggregates. Energy dispersive spectrometric analysis showed that exopolymeric material acts as a nucleation site for Mn deposition and oxide formation which occurs in the form of microspherical aggregates. These features show striking resemblance to biogenically produced Fe-Mn oxide deposits from Lau Basin. Surprisingly, diffractograms of auto-oxidized and bacterially formed Mn-oxide showed similarities to the hydrothermal vein mineral Rhodochrosite indicating that it can also be produced biotically. Elongation of cells by up to 4× the original size and distortion in cell shape were evident at Mn (II) concentrations >100 µmol L-1 . Marked differences in C-substrate utilization by the test strains were also observed in presence of Mn (II). A shift in use of substrates that are readily available in oceanic waters like N-acetyl-d-glucosamine to those that can be used under changing redox conditions (d-cellobiose) or in the presence of metal ions (d-arabinose, l-asparagine) were observed. These findings highlight the significant role of autochthonous bacteria in transforming reduced metal ions and aiding in the formation of metal oxides. Under natural or laboratory conditions, the mode of bacterially generated Mn-oxide tends to remain the same.

Genomic and physiological characterization and description of Marinobacter gelidimuriae sp. nov., a psychrophilic, moderate halophile from Blood Falls, an antarctic subglacial brine.

Antarctic subice environments are diverse, underexplored microbial habitats. Here, we describe the ecophysiology and annotated genome of a Marinobacter strain isolated from a cold, saline, iron-rich subglacial outflow of the Taylor Glacier, Antarctica. This strain (BF04_CF4) grows fastest at neutral pH (range 6-10), is psychrophilic (range: 0°C-20°C), moderately halophilic (range: 0.8%-15% NaCl) and hosts genes encoding potential low temperature and high salt adaptations. The predicted proteome suggests it utilizes fewer charged amino acids than a mesophilic Marinobacter strain. BF04_CF4 has increased concentrations of membrane unsaturated fatty acids including palmitoleic (33%) and oleic (27.5%) acids that may help maintain cell membrane fluidity at low temperatures. The genome encodes proteins for compatible solute biosynthesis and transport, which are known to be important for growth in saline environments. Physiological verification of predicted metabolic functions demonstrate BF04_CF4 is capable of denitrification and may facilitate iron oxidation. Our data indicate that strain BF04_CF4 represents a new Marinobacter species, Marinobacter gelidimuriae sp. nov., that appears well suited for the subglacial environment it was isolated from. Marinobacter species have been isolated from other cold, saline environments in the McMurdo Dry Valleys and permanently cold environments globally suggesting that this lineage is cosmopolitan and ecologically relevant in icy brines.

Periodically spilled-oil input as a trigger to stimulate the development of hydrocarbon-degrading consortia in a beach ecosystem.

In this study, time-series samples were taken from a gravel beach to ascertain whether a periodic oil input induced by tidal action at the early stage of an oil spill can be a trigger to stimulate the development of hydrocarbon-degrading bacteria under natural in situ attenuation. High-throughput sequencing shows that the microbial community in beach sediments is characterized by the enrichment of hydrocarbon-degrading bacteria, including Alcanivorax, Dietzia, and Marinobacter. Accompanying the periodic floating-oil input, dynamic successions of microbial communities and corresponding fluctuations in functional genes (alkB and RDH) are clearly indicated in a time sequence, which keeps pace with the ongoing biodegradation of the spilled oil. The microbial succession that accompanies tidal action could benefit from the enhanced exchange of oxygen and nutrients; however, regular inputs of floating oil can be a trigger to stimulate an in situ "seed bank" of hydrocarbon-degrading bacteria. This leads to the continued blooming of hydrocarbon-degrading consortia in beach ecosystems. The results provide new insights into the beach microbial community structure and function in response to oil spills.

Marinobacter salexigens sp. nov., isolated from marine sediment.

A novel bacterium, designated as strain HJR7T, was isolated from a marine sediment sample collected from the coastal area of Weihai, China (121° 57' E, 37° 29' N). Cells were Gram-stain-negative, facultative anaerobic, non-motile and rod-shaped. The temperature, pH and NaCl ranges for growth were determined as 4-40 °C, pH 6.5-9.5 and 0.5-15.0 % (w/v), respectively. Phylogenetic analysis based on the 16S rRNA gene sequences indicated that strain HJR7T belongs to the genus Marinobacter in the family Alteromonadaceae. The most closely related species were Marinobacter aromaticivorans (97.6 % 16S rRNA gene sequence similarity) and Marinobacter maritimus (97.3 % similarity). Ubiquinone 9 (Q-9) was the only respiratory quinone detected in strain HJR7T. The major fatty acids of strain HJR7T were C12 : 0, C16 : 0, C16 : 0 N alcohol, C18 : 1ω9c and C18 : 3ω6, 9, 12c. The major polar lipids were phosphatidylglycerol, phosphatidylethanolamine, and an unidentified phospholipid. The DNA G+C content of strain HJR7T was 53.7 mol%. On the basis of phylogenetic, genotypic, phenotypic, and chemotaxonomic analyses, strain HJR7T represents a novel species within the genus Marinobacter, for which the name Marinobacter salexigens sp. nov. is proposed. The type strain is HJR7T (=KCTC 52545T=MCCC 1H00176T).

Marinobacter aquaticus sp. nov., a moderately halophilic bacterium from a solar saltern.

A moderately halophilic bacterium designated strain M6-53T was isolated from water of a pond from a marine saltern located in Huelva, south-west Spain. Cells of the strain were Gram-stain-negative, strictly aerobic, motile, slightly curved rods, able to grow in media containing 5-25 % (w/v) NaCl (optimal growth at 10 %, w/v), at temperatures from 20 to 40 °C (optimally at 37 °C) and at pH 6.5-9 (optimally at pH 7.0). Phylogenetic analysis based on 16S rRNA gene sequences placed the new isolate within the genus Marinobacter, with the type strains of the most closely related species being Marinobacter persicus IBRC-M 10445T (98.5 % similarity), Marinobacter oulmenensis Set74T (97.2 %) and Marinobacter hydrocarbonoclasticus ATCC 49840T (97.1 %). The major fatty acids present in strain M6-53T were C18 : 1ω9c (29.5 %), C16 : 0 (26.7 %), C12 : 0 3-OH (15.1 %), C18 : 0 (10.2 %) and C16 : ω9c (9.6 %). The G+C content of the genomic DNA for this strain was determined to be 56.4 mol%. The DNA-DNA hybridization values between strain M6-53T and M. persicus CECT 7991T, M. oulmenensis CECT 7499T and M. hydrocarbonoclasticus DSM 50418 were 8, 41 and 38 %, respectively. These values are lower than the accepted 70 % threshold and showed that the new isolate represented a different species within the genus Marinobacter. Phylogenetic analysis based on the 16S rRNA gene sequence and the phenotypic, genotypic and chemotaxonomic features of this new isolate support the placement of strain M6-53T as a representative of a novel species of the genus Marinobacter, for which we propose the name Marinobacter aquaticus sp. nov., with strain M6-53T (=CECT 9228T=LMG 30006T) as the type strain.

Marinobacter lipolyticus from Red Sea for lipase production and modulation of silver nanomaterials for anti-candidal activities.

In this study, the bacterial strain CEES 33 was isolated from the coastal area of the Red Sea, Jeddah, Kingdom of Saudi Arabia. The bacterium isolate was identified and characterized by using biochemical and molecular methods. The isolate CEES 33 has been identified as Gram-negative rod shaped and cream pigmented spherical colonies. It also demonstrated a positive result for nitrate reduction, oxidase, catalase, citrate utilization, lipase and exopolysaccharide production. Strain CEES 33 was characterized at the molecular level by partial 16S rRNA sequencing and it has been identified as Marinobacter lipolyticus (EMBL|LN835275.1). The lipolytic activity of the isolate was also observed 2.105 nkatml-1. Furthermore, the bacterial aqueous extract was used for green synthesis of silver nanoparticles (AgNPs), which was further confirmed by UV-visible spectra (430 nm), XRD and SEM analysis. Moreover, the biological functional group that involved in AgNPs synthesis was confirmed by FTIR spectra. The biological activities of AgNPs were also investigated, which showed a significant growth inhibition of Candida albicans with 16 ± 2 mm zone of inhibition at 10 µg dose/wells. Therefore, bacterium Marinobacter lipolyticus might be used in future for lipase production and nanoparticles fabrication for biomedical application, to control fungal diseases caused by C. albicans.