Marinobacter maritimus sp. nov., a psychrotolerant strain isolated from sea water off the subantarctic Kerguelen islands

Marinobacter qingdaonensis sp. nov., a moderately halotolerant bacterium isolated from intertidal sediment

A Gram-stain-negative, aerobic, rod-shaped and halotolerant bacterium, designated as strain ASW11-75T, was isolated from intertidal sediments in Qingdao, PR China, and identified using a polyphasic taxonomic approach. Growth of strain ASW11-75T occurred at 10-45 °C (optimum, 37 °C), pH 6.5-9.0 (optimum, pH 8.0) and 0.5-18.0 % NaCl concentrations (optimum, 2.5 %). Phylogenetic analyses based on 16S rRNA gene sequences and 1179 single-copy orthologous clusters indicated that strain ASW11-75T is affiliated with the genus Marinobacter. Strain ASW11-75T showed highest 16S rRNA gene sequence similarity to 'Marinobacter arenosus' CAU 1620T (98.5 %). The digital DNA-DNA hybridization and average nucleotide identity values between strain ASW11-75T and its closely related strains (Marinobacter salarius R9SW1T, Marinobacter similis A3d10T, 'Marinobacter arenosus' CAU 1620T, Marinobacter sediminum R65T, Marinobacter salinus Hb8T, Marinobacter alexandrii LZ-8T and Marinobacter nauticus ATCC 49840T) were 19.8-24.5 % and 76.6-80.7 %, respectively. The predominant cellular fatty acids were C16 : 0, C18 : 1  ω9c and C16 : 0 N alcohol. The polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified aminophospholipid and two unidentified lipids. The major isoprenoid quinone was ubiquinone-9. The genomic DNA G+C content was 62.2 mol%. Based on genomic and gene function analysis, strain ASW11-75T had lower protein isoelectric points with higher ratios of acidic residues to basic residues and possessed genes related to ion transport and organic osmoprotectant uptake, implying its potential tolerance to salt. The results of polyphasic characterization indicated strain ASW11-75T represents a novel Marinobacter species, for which the name Marinobacter qingdaonensis sp. nov. with the type strain ASW11-75T is proposed. The type strain is ASW11-75T (=KCTC 82497T=MCCC 1K05587T).

Complete genome sequence of PETase type IIa-harboring Marinobacter nanhaiticus D15-8W, isolated from a South China Sea sediment

Marinobacter nanhaiticus D15-8W is known for its ability to metabolize polycyclic aromatic hydrocarbons. Here, we report the complete circular genome sequence of this strain to be 5,336,660 bp (G + C content, 58.6%; 4,869 protein-coding sequences) with one plasmid (69,655 bp).

Evolutionary Divergence of Marinobacter Strains in Cryopeg Brines as Revealed by Pangenomics

Marinobacter spp. are cosmopolitan in saline environments, displaying a diverse set of metabolisms that allow them to competitively occupy these environments, some of which can be extreme in both salinity and temperature. Here, we introduce a distinct cluster of Marinobacter genomes, composed of novel isolates and in silico assembled genomes obtained from subzero, hypersaline cryopeg brines, relic seawater-derived liquid habitats within permafrost sampled near Utqiaġvik, Alaska. Using these new genomes and 45 representative publicly available genomes of Marinobacter spp. from other settings, we assembled a pangenome to examine how the new extremophile members fit evolutionarily and ecologically, based on genetic potential and environmental source. This first genus-wide genomic analysis revealed that Marinobacter spp. in general encode metabolic pathways that are thermodynamically favored at low temperature, cover a broad range of organic compounds, and optimize protein usage, e.g., the Entner–Doudoroff pathway, the glyoxylate shunt, and amino acid metabolism. The new isolates contributed to a distinct clade of subzero brine-dwelling Marinobacter spp. that diverged genotypically and phylogenetically from all other Marinobacter members. The subzero brine clade displays genomic characteristics that may explain competitive adaptations to the extreme environments they inhabit, including more abundant membrane transport systems (e.g., for organic substrates, compatible solutes, and ions) and stress-induced transcriptional regulatory mechanisms (e.g., for cold and salt stress) than in the other Marinobacter clades. We also identified more abundant signatures of potential horizontal transfer of genes involved in transcription, the mobilome, and a variety of metabolite exchange systems, which led to considering the importance of this evolutionary mechanism in an extreme environment where adaptation via vertical evolution is physiologically rate limited. Assessing these new extremophile genomes in a pangenomic context has provided a unique view into the ecological and evolutionary history of the genus Marinobacter, particularly with regard to its remarkable diversity and its opportunism in extremely cold and saline environments.

Loss of Motility as a Non-Lethal Mechanism for Intercolony Inhibition ("Sibling Rivalry") in Marinobacter

Bacteria from the genus Marinobacter are ubiquitous throughout the worlds' oceans as "opportunitrophs" capable of surviving a wide range of conditions, including colonization of surfaces of marine snow and algae. To prevent too many bacteria from occupying this ecological niche simultaneously, some sort of population dependent control must be operative. Here, we show that while Marinobacter do not produce or utilize an acylhomoserine lactone (AHL)-based quorum sensing system, "sibling" colonies of many species of Marinobacter exhibit a form of non-lethal chemical communication that prevents colonies from overrunning each other's niche space. Evidence suggests that this inhibition is the result of a loss in motility for cells at the colony interfaces. Although not the signal itself, we have identified a protein, glycerophosphoryl diester phosphodiesterase, that is enriched in the inhibition zone between the spreading colonies that may be part of the overall response.

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).

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

An aerobic, Gram-stain-negative bacterium, designated CLL7-20^T, was isolated from a marine sediment sample from offshore of Changyi, Shandong Province, China. Cells of strain CLL7-20^T 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 CLL7-20^T were C_16 : 0 and summed feature 3 (C_16 : 1 ω7c/C_16 : 1 ω6c). The main polar lipids of strain CLL7-20^T were phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG) and an unidentified aminolipid (AL). Strain CLL7-20^T contained Q-9 as the major respiratory quinone. The G+C content of its genomic DNA was 56.2 mol%. Phylogenetically, strain CLL7-20^T branched within the genus Marinobacter, with M. daqiaonensis YCSA40^T being its closest phylogenetic relative (96.7 % 16S rRNA gene sequence similarity), followed by M. sediminum R65^T (96.6 %). Average nucleotide identity and in silico DNA-DNA hybridization values between strain CLL7-20^T 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 CLL7-20^T (=MCCC 1A14855^T=KCTC 72664^T) 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 CLL7-20^T, which indicate its potential as a promising alternative to chemical fertilizers in iron-limitated environments such as saline soils.

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.

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 PWS21^T, 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 PWS21^T is closely related to Marinobacter guineae M3B^T (98.4%) and Marinobacter lipolyticus SM19^T (98.2%). Multilocus sequence analysis (MLSA) based on sequences of housekeeping genes gyrB, recA, atpD, rpoB and rpoD indicates that strain PWS21^T represents a distinct evolutionary lineage within the genus Marinobacter. Furthermore, strain PWS21^T showed low ANI and diDDH values to the closely related species. The principal fatty acids were identified as C_12:0, C_12:0 3-OH, C_16:1ω9c, C_16:0 and C_18:1ω9c. 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 PWS21^T represents a novel species of the genus Marinobacter, for which the name Marinobacter profundi sp. nov. is proposed (type strain PWS21^T = KCTC 52990^T = MCCC 1K03345^T).

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 T17^T, 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 T17^T exhibited the highest similarity values to those of the type strain Marinobacter lacisalsi FP2.5 (96.2 %) and Marinobacter koreensis DD-M3^T (96.2 %). Strain T17^T 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 T17^T was identified as Q-9. The major fatty acids of strain T17^T were C12 : 0, C16 : 0 and C16 : 0 10-CH3. The major polar lipids of strain T17^T were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidglycerol, an unidentified aminolipid and an unidentified phospholipid. The DNA G+C content of strain T17^T was 63.0 mol%. The draft genome sequence of strain T17^T 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 NKSG1^T, Marinobacter segnicrescens SS11B1-4^T and Marinobacter daqiaonensis CGMCC 1.9167^T, respectively. On the basis of the phenotypic, phylogenetic, genomic and chemotaxonomic properties, strain T17^T is considered to represent a novel species within the genus Marinobacter, for which the name Marinobacterbohaiensis sp. nov. is proposed. The type strain is T17^T (=KCTC 52710^T=MCCC 1K03282^T).

Draft Genome Sequence of Marinobacter sp. Strain ANT_B65, Isolated from Antarctic Marine Sponge

Marinobacter sp. strain ANT_B65 was isolated from sponge collected in King George Island, Antarctica. The draft genome of 4,173,840 bp encodes 3,743 protein-coding open reading frames. The genome will provide insights into the strain’s potential use in the production of natural products.

Marinobacter salexigens sp. nov., isolated from marine sediment

A novel bacterium, designated as strain HJR7^T, 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 HJR7^T 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 HJR7^T. The major fatty acids of strain HJR7^T 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 HJR7^T was 53.7 mol%. On the basis of phylogenetic, genotypic, phenotypic, and chemotaxonomic analyses, strain HJR7^T represents a novel species within the genus Marinobacter, for which the name Marinobacter salexigens sp. nov. is proposed. The type strain is HJR7^T (=KCTC 52545^T=MCCC 1H00176^T).

Draft Genome Sequence of a Novel Marinobacter sp. Strain from Honolulu Harbor, Hawai'i

Marinobacter sp. strain X15-166B^T was cultivated from sediment in Honolulu Harbor, Hawai‘i. The X15-166B^T draft genome of 3,490,661 bp encodes 3,115 protein-coding open reading frames. We anticipate that the genome will provide insights into the strain’s lifestyle and the evolution of Marinobacter.

Cold Stress Tolerance in Psychrotolerant Soil Bacteria and Their Conferred Chilling Resistance in Tomato (Solanum lycopersicum Mill.) under Low Temperatures

The present work aimed to study the culturable diversity of psychrotolerant bacteria persistent in soil under overwintering conditions, evaluate their ability to sustain plant growth and alleviate chilling stress in tomato. Psychrotolerant bacteria were isolated from agricultural field soil samples colleced during winter and then used to study chilling stress alleviation in tomato plants (Solanum lycopersicum cv Mill). Selective isolation after enrichment at 5°C yielded 40 bacterial isolates. Phylogenetic studies indicated their distribution in genera Arthrobacter, Flavimonas, Flavobacterium, Massilia, Pedobacter and Pseudomonas. Strains OS211, OB146, OB155 and OS261 consistently improved germination and plant growth when a chilling stress of 15°C was imposed and therefore were selected for pot experiments. Tomato plants treated with the selected four isolates exhibited significant tolerance to chilling as observed through reduction in membrane damage and activation of antioxidant enzymes along with proline synthesis in the leaves when exposed to chilling temperature conditions (15°C). Psychrotolerant physiology of the isolated bacteria combined with their ability to improve germination, plant growth and induce antioxidant capacity in tomato plants can be employed to protect plants against chilling stress.

Consistent Occurrence of Hydrocarbonoclastic Marinobacter Strains in Various Cultures of Picocyanobacteria from the Arabian Gulf: Promising Associations for Biodegradation of Marine Oil Pollution

Fifteen nonaxenic cultures of picocyanobacteria were isolated from the Arabian Gulf, from which 122 heterotrophic bacterial strains were obtained. Based on their 16S rRNA gene sequences, those strains were affiliated with 22 different species, 82.8% of which belonged to the genus Marinobacter, known to comprise hydrocarbonoclastic strains. The remaining species belonged to the genera Alcanivorax, Bacillus, Halomonas, Mesorhizobium, and Paenibacillus, and a Bacteriodetes bacterium also known to comprise hydrocarbonoclastic strains. All the picocyanobacterial cultures harbored one or more strains of Marinobacter. Marinobacter in addition to Alcanivorax and other genera isolated from those picocyanobacteria grew on Tween 80, crude oil, and pure hydrocarbons as sole sources of carbon and energy, i.e. they are related to the obligate hydrocarbonoclastic bacteria group. They consumed crude oil, n-octadecane, and phenanthrene in batch cultures. The results indicated that Marinobacter isolates seemed to grow better and consume more oil in the presence of their host picocyanobacteria than in their absence. Such natural microbial associations assumingly play a role in bioremediation of spilled hydrocarbons in the Arabian Gulf. Similar associations probably occur in other marine environments as well and are active in oil spill removal.

Marinobacter nitratireducens sp. nov., a halophilic and lipolytic bacterium isolated from coastal surface sea water

A novel Gram-stain-negative, rod-shaped, motile bacterium, designated strain AK21T, was isolated from coastal surface sea water at Visakhapatnam, India. The strain was positive for oxidase, catalase, lipase, l-proline arylamidase and tyrosine arylamidase activities. The predominant fatty acids were C12:0, C12:0 3-OH, C16:0, C16:1ω9c, C18:1ω9c and summed feature 3 (C16:1ω7c and/or iso-C15:0 2-OH). The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, one unidentified aminophospholipid, two unidentified phospholipids and one unidentified lipid. Q-10 was the predominant respiratory quinone. The DNA G+C content of the strain was 54.6 mol%. 16S rRNA gene sequence analysis indicated that strain AK21T was a member of the genus Marinobacter and was closely related to Marinobacter xestospongiae, with pairwise sequence similarity of 97.2 % to the type strain, with similarity to other members of the genus of 94.0–96.8 %. The mean DNA–DNA relatedness of strain AK21T with M. xestospongiae JCM 17469T was 34.5 %, and relatedness with Marinobacter mobilis JCM 15154T was 40.5 %. Phylogenetic analysis showed that strain AK21T clustered with the type strains of M. xestospongiae and M. mobilis at distances of 2.9 and 2.8 % (97.1 and 97.2 % similarity), respectively. Based on the phenotypic characteristics and on phylogenetic inference, it appears that strain AK21T represents a novel species of the genus Marinobacter, for which the name Marinobacter nitratireducens sp. nov. is proposed. The type strain of Marinobacter nitratireducens is AK21T ( = MTCC 11704T = JCM 18428T).

Marinobacter halophilus sp. nov., a halophilic bacterium isolated from a salt lake

A Gram-staining-negative bacterium, strain XCD-X12(T), was isolated from Xiaochaidan Lake, a salt lake (salinity 9.9%, w/w) in Qaidam basin, Qinghai Province, China. Its taxonomic position was determined by using a polyphasic approach. Cells of strain XCD-X12(T) were non-spore-forming rods, 0.4-0.7 μm wide, 2.1-3.2 μm long and motile with a single polar flagellum. Strain XCD-X12(T) was strictly aerobic and catalase- and oxidase-positive. Growth was observed in the presence of 0-20.0% (w/v) NaCl (optimum, 4.0-8.0%), at 4-35 °C (optimum, 30 °C) and at pH 6.5-10.5 (optimum, pH 8.5). It contained Q-9 as the predominant respiratory quinone. The major fatty acids (>10.0%) were C16 : 0, C16 : 1ω9c and C18 : 1ω9c. The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, two unknown phospholipids and an uncharacterized aminophospholipid. The DNA G+C content was 55.6 mol% (Tm). Phylogenetic trees based on 16S rRNA gene sequences showed that strain XCD-X12(T) was associated with the genus Marinobacter, and showed the highest 16S rRNA gene sequence similarity to Marinobacter hydrocarbonoclasticus ATCC 49840(T) (97.4%), M. vinifirmus FB1(T) (96.8%), M. excellens KMM 3809(T) (96.8%) and M. antarcticus ZS2-30(T) (96.7%). DNA-DNA relatedness of strain XCD-X12(T) to M. hydrocarbonoclasticus CGMCC 1.7683(T) was 34 ± 5%. Based on these data, it is concluded that strain XCD-X12(T) represents a novel species of the genus Marinobacter, for which the name Marinobacter halophilus sp. nov. is proposed. The type strain is XCD-X12(T) ( = CGMCC 1.12481(T)= JCM 30472(T)).

Marinobacter shengliensis sp. nov., a moderately halophilic bacterium isolated from oil-contaminated saline soil

Two moderately halophilic strains, designated SL013A34A2(T) and SL013A24A, were isolated from oil-contaminated saline soil from Shengli Oilfield, eastern China. Cells were found to be Gram-staining negative, aerobic, rod-shaped with a single polar flagellum. The isolates were found to grow at 10-40 °C (optimum 35 °C), pH 6.0-9.0 (optimum pH 8.0), and NaCl concentrations of 0.5-18.0 % (w/v) (optimum 3.0-6.0 NaCl). The 16S rRNA gene sequence analysis indicated that the isolates belong to the genus Marinobacter. Strain SL013A34A2(T) shares the highest 16S rRNA gene sequence similarities with strain SL013A24A (99.3 %), followed by M. hydrocarbonoclasticus CGMCC 1.7683(T) (97.8 %), M. vinifirmus CGMCC 1.7265(T) (97.8 %), and M. excellens KMM 3809(T) (97.4 %), respectively, but low similarities (93.8-96.4 %) with type strains of the other numbers of genus Marinobacter. DNA-DNA relatedness values of strain SL013A34A2(T) with strains SL013A24A, M. hydrocarbonoclasticus CGMCC 1.7683(T), M. vinifirmus CGMCC 1.7265(T) and M. excellens KMM 3809(T) were 88.7, 29.2, 33.4 and 29.4 %, respectively. The major fatty acids of strain SL013A34A2(T) were identified as C18:1 ω9c, C16:0, C12:03-OH, C12:0, C16:1 ω9c and 10-methyl C18:0. The major respiratory quinone of strain SL013A34A2(T) was found to be ubiquinone-9, and its predominant polar lipids were identified as diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol and unidentified glycolipid. The genomic DNA G + C content was found to be 56.1 mol %. Based on the phenotypic, genetic and chemotaxonomic characteristics, these two isolates are representatives of a novel species of the genus Marinobacter, for which the name Marinobacter shengliensis sp. nov. is proposed. The type strain is SL013A34A2(T)(=LMG 27740(T) = CGMCC 1.12758(T)).

Marinobacter salarius sp. nov. and Marinobacter similis sp. nov., isolated from sea water

Two non-pigmented, motile, Gram-negative marine bacteria designated R9SW1T and A3d10T were isolated from sea water samples collected from Chazhma Bay, Gulf of Peter the Great, Sea of Japan, Pacific Ocean, Russia and St. Kilda Beach, Port Phillip Bay, the Tasman Sea, Pacific Ocean, respectively. Both organisms were found to grow between 4 °C and 40 °C, between pH 6 to 9, and are moderately halophilic, tolerating up to 20% (w/v) NaCl. Both strains were found to be able to degrade Tween 40 and 80, but only strain R9SW1T was found to be able to degrade starch. The major fatty acids were characteristic for the genus Marinobacter including C16:0, C16:1ω7c, C18:1ω9c and C18:1ω7c. The G+C content of the DNA for strains R9SW1T and A3d10T were determined to be 57.1 mol% and 57.6 mol%, respectively. The two new strains share 97.6% of their 16S rRNA gene sequences, with 82.3% similarity in the average nucleotide identity (ANI), 19.8% similarity in the in silico genome-to-genome distance (GGD), 68.1% similarity in the average amino acid identity (AAI) of all conserved protein-coding genes, and 31 of the Karlin's genomic signature dissimilarity. A phylogenetic analysis showed that R9SW1T clusters with M. algicola DG893T sharing 99.40%, and A3d10T clusters with M. sediminum R65T sharing 99.53% of 16S rRNA gene sequence similarities. The results of the genomic and polyphasic taxonomic study, including genomic, genetic, phenotypic, chemotaxonomic and phylogenetic analyses based on the 16S rRNA, gyrB and rpoD gene sequence similarities, the analysis of the protein profiles generated using MALDI-TOF mass spectrometry, and DNA-DNA relatedness data, indicated that strains R9SW1T and A3d10(T) represent two novel species of the genus Marinobacter. The names Marinobacter salarius sp. nov., with the type strain R9SW1(T) ( =  LMG 27497(T)  =  JCM 19399(T)  =  CIP 110588(T)  =  KMM 7502(T)) and Marinobacter similis sp. nov., with the type strain A3d10(T) ( =  JCM 19398(T)  =  CIP 110589(T)  =  KMM 7501T), are proposed.

Genome Sequence of the Polycyclic Aromatic Hydrocarbon-Degrading Bacterium Strain Marinobacter nanhaiticus D15-8WT

Marinobacter nanhaiticus strain D15-8W^T was isolated from a phenanthrene-degrading consortium, enriched from sediment of the South China Sea. Here, we present the draft genome of strain D15-8W^T, which contains 5,358,309 bp with a G+C content of 58.53% and contains 4,829 protein-coding genes and 47 tRNA genes.

Biogeochemical implications of the ubiquitous colonization of marine habitats and redox gradients by Marinobacter species

The Marinobacter genus comprises widespread marine bacteria, found in localities as diverse as the deep ocean, coastal seawater and sediment, hydrothermal settings, oceanic basalt, sea-ice, sand, solar salterns, and oil fields. Terrestrial sources include saline soil and wine-barrel-decalcification wastewater. The genus was designated in 1992 for the Gram-negative, hydrocarbon-degrading bacterium Marinobacter hydrocarbonoclasticus. Since then, a further 31 type strains have been designated. Nonetheless, the metabolic range of many Marinobacter species remains largely unexplored. Most species have been classified as aerobic heterotrophs, and assessed for limited anaerobic pathways (fermentation or nitrate reduction), whereas studies of low-temperature hydrothermal sediments, basalt at oceanic spreading centers, and phytoplankton have identified species that possess a respiratory repertoire with significant biogeochemical implications. Notable physiological traits include nitrate-dependent Fe(II)-oxidation, arsenic and fumarate redox cycling, and Mn(II) oxidation. There is also evidence for Fe(III) reduction, and metal(loid) detoxification. Considering the ubiquity and metabolic capabilities of the genus, Marinobacter species may perform an important and underestimated role in the biogeochemical cycling of organics and metals in varied marine habitats, and spanning aerobic-to-anoxic redox gradients.

Oil-bioremediation potential of two hydrocarbonoclastic, diazotrophic Marinobacter strains from hypersaline areas along the Arabian Gulf coasts

Two halophilic, hydrocarbonoclastics bacteria, Marinobacter sedimentarum and M. flavimaris, with diazotrophic potential occured in hypersaline waters and soils in southern and northern coasts of Kuwait. Their numbers were in the magnitude of 10(3) colony forming units g(-1). The ambient salinity in the hypersaline environments was between 3.2 and 3.5 M NaCl. The partial 16S rRNA gene sequences of the two strains showed, respectively, 99 and 100% similarities to the sequences in the GenBank. The two strains failed to grow in the absence of NaCl, exhibited best growth and hydrocarbon biodegradation in the presence of 1 to 1.5 M NaCl, and still grew and maintained their hydrocarbonoclastic activity at salinities up to 5 M NaCl. Both species utilized Tween 80, a wide range of individual aliphatic hydrocarbons (C9-C40) and the aromatics benzene, biphenyl, phenanthrene, anthracene and naphthalene as sole sources of carbon and energy. Experimental evidence was provided for their nitrogen-fixation potential. The two halophilic Marinobacter strains successfully mineralized crude oil in nutrient media as well as in hypersaline soil and water microcosms without the use of any nitrogen fertilizers.

Catenovulum agarivorans gen. nov., sp. nov., a peritrichously flagellated, chain-forming, agar-hydrolysing gammaproteobacterium from seawater

A novel Gram-negative, strictly aerobic, agar-hydrolysing bacterium, designated YM01T, was isolated from seawater samples collected from the Yellow Sea (coastal region of Qingdao, PR China). Cells were rod-shaped, peritrichously flagellated and formed long chains end-to-end. The isolate had an absolute requirement for Na+ ions, but not seawater, for growth and grew optimally at about 28 °C, in 2 % NaCl and at pH 8.0–9.0. The isolate could not be cultured in marine broth 2216, but grew well on marine agar 2216. YM01T was able to hydrolyse cellulose, starch, aesculin and Tween 80, but not egg yolk, gelatin, urea or casein. 16S rRNA gene sequence analysis demonstrated that this isolate was unique, showing only 88.4–91.0 % sequence similarity to its closest neighbours, including members of the genera Glaciecola (88.4–91.0 %), Alteromonas (88.7–89.6 %), Aestuariibacter (89.3–90.4 %), Salinimonas (89.0 %), Bowmanella (90.1–90.3 %) and Agarivorans (88.5–89.9 %). Phylogenetic analyses demonstrated that strain YM01T formed a distinct clade closely related to species of the family Alteromonadaceae within the group of Alteromonas-like gammaproteobacteria. It contained menaquinone MK-7 as the predominant isoprenoid quinone and C16 : 0 (38.3 %), C16 : 1ω7c and/or iso-C15 : 0 2-OH (29.0 %), C18 : 1ω7c (9.3 %) and C10 : 0 3-OH (8.2 %) as major cellular fatty acids. Phosphatidylethanolamine, phosphatidylglycerol and an aminophospholipid were the major phospholipid constituents. The DNA G+C content was 44.8 mol%. Based on its phenotypic, chemotaxonomic and phylogenetic distinctiveness, strain YM01T is considered to represent a novel species in a new genus in the Gammaproteobacteria, for which the name Catenovulum agarivorans gen. nov., sp. nov. is proposed; the type strain of Catenovulum agarivorans is YM01T ( = CGMCC 1.10245T  = DSM 23111T  = JCM 16580T).

Marinobacter antarcticus sp. nov., a halotolerant bacterium isolated from Antarctic intertidal sandy sediment

A Gram-staining-negative, aerobic, motile, oxidase- and catalase-positive, rod-shaped strain, designated ZS2-30(T), was isolated from Antarctic intertidal sandy sediment. The strain grew at 4-35 °C (optimum, 25 °C) and in 0-25% (w/v) NaCl (optimum, 3.0-4.0%). It could reduce nitrate to nitrite and hydrolyse Tween 80. The predominant cellular fatty acids of strain ZS2-30(T) were summed feature 3 (C(16:1)ω7c and/or C(16:1)ω6c), C(16:0), C(18:1)ω9c, C(16:1)ω9c, C(12:0) 3-OH and C(12:0). The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and an unidentified aminophospholipid. The genomic DNA G+C content of strain ZS2-30(T) was 55.8 mol%. Analyses of 16S rRNA gene sequences revealed that strain ZS2-30(T) was affiliated with the genus Marinobacter. It showed highest 16S rRNA gene sequence similarities to the type strains of three species of the genus Marinobacter, namely Marinobacter maritimus (98.3%), Marinobacter psychrophilus (98.1%) and Marinobacter goseongensis (97.1%), but the DNA-DNA relatedness values between strain ZS2-30(T) and the above three species were all lower than 45%. Moreover, strain ZS2-30(T) could be distinguished from closely related species of the genus Marinobacter by various phenotypic properties. Based on this taxonomic study using a polyphasic approach, strain ZS2-30(T) is considered to represent a novel species in the genus Marinobacter, for which the name Marinobacter antarcticus sp. nov. is proposed. The type strain of Marinobacter antarcticus is ZS2-30(T) ( = CGMCC 1.10835(T) = KCTC 23684(T)).

Low temperature S(0) biomineralization at a supraglacial spring system in the Canadian High Arctic

Elemental sulfur (S(0) ) is deposited each summer onto surface ice at Borup Fiord pass on Ellesmere Island, Canada, when high concentrations of aqueous H(2) S are discharged from a supraglacial spring system. 16S rRNA gene clone libraries generated from sulfur deposits were dominated by β-Proteobacteria, particularly Ralstonia sp. Sulfur-cycling micro-organisms such as Thiomicrospira sp., and ε-Proteobacteria such as Sulfuricurvales and Sulfurovumales spp. were also abundant. Concurrent cultivation experiments isolated psychrophilic, sulfide-oxidizing consortia, which produce S(0) in opposing gradients of Na(2) S and oxygen. 16S rRNA gene analyses of sulfur precipitated in gradient tubes show stable sulfur-biomineralizing consortia dominated by Marinobacter sp. in association with Shewanella, Loktanella, Rubrobacter, Flavobacterium, and Sphingomonas spp. Organisms closely related to cultivars appear in environmental 16S rRNA clone libraries; none currently known to oxidize sulfide. Once consortia were simplified to Marinobacter and Flavobacteria spp. through dilution-to-extinction and agar removal, sulfur biomineralization continued. Shewanella, Loktanella, Sphingomonas, and Devosia spp. were also isolated on heterotrophic media, but none produced S(0) alone when reintroduced to Na(2) S gradient tubes. Tubes inoculated with a Marinobacter and Shewanella spp. co-culture did show sulfur biomineralization, suggesting that Marinobacter may be the key sulfide oxidizer in laboratory experiments. Light, florescence and scanning electron microscopy of mineral aggregates produced in Marinobacter experiments revealed abundant cells, with filaments and sheaths variably mineralized with extracellular submicron sulfur grains; similar biomineralization was not observed in abiotic controls. Detailed characterization of mineral products associated with low temperature microbial sulfur-cycling may provide biosignatures relevant to future exploration of Europa and Mars.

Genomic potential of Marinobacter aquaeolei, a biogeochemical "opportunitroph"

The genus of Marinobacter is one of the most ubiquitous in the global oceans and assumed to significantly impact various biogeochemical cycles. The genome structure and content of Marinobacter aquaeolei VT8 was analyzed and compared with those from other organisms with diverse adaptive strategies. Here, we report the many "opportunitrophic" genetic characteristics and strategies that M. aquaeolei has adopted to promote survival under various environmental conditions. Genome analysis revealed its metabolic potential to utilize oxygen and nitrate as terminal electron acceptors, iron as an electron donor, and urea, phosphonate, and various hydrocarbons as alternative N, P, and C sources, respectively. Miscellaneous sensory and defense mechanisms, apparently acquired via horizontal gene transfer, are involved in the perception of environmental fluctuations and antibiotic, phage, toxin, and heavy metal resistance, enabling survival under adverse conditions, such as oil-polluted water. Multiple putative integrases, transposases, and plasmids appear to have introduced additional metabolic potential, such as phosphonate degradation. The genomic potential of M. aquaeolei and its similarity to other opportunitrophs are consistent with its cosmopolitan occurrence in diverse environments and highly variable lifestyles.

Marinobacter daqiaonensis sp. nov., a moderate halophile isolated from a Yellow Sea salt pond

A Gram-negative, oxidase- and catalase-positive, moderately halophilic strain, designated YCSA40(T), was isolated from sediment of Daqiao saltern in Qingdao, on the east coast of China. Growth occurred at 10-45 °C, at pH 5-9 and with 1-15% NaCl. Strain YCSA40(T) showed the highest 16S rRNA gene sequence similarity to Marinobacter segnicrescens SS011B1-4(T) (97%) and M. gudaonensis SL014B61A(T) (96.9%) and 16S rRNA gene sequence phylogenetic analysis assigned the isolate to the genus Marinobacter. Strain YCSA40(T) contained C(18:1)ω9c (34.8%), C(16:0) (11.6%), C(19:0) cyclo ω10c/C(19:1)ω6c (10.5%), C(16:1)ω9c (8.4%), C(17:0) (6.3%) and C(12:0) 3-OH (5.8%) as the predominant fatty acids. The DNA G+C content was 60.8 mol% and the major ubiquinone was Q-9. These chemotaxonomic characters were all consistent with membership of the genus Marinobacter. DNA-DNA relatedness between the isolate and M. segnicrescens CGMCC 1.6489(T), M. gudaonensis CGMCC 1.6294(T) and other type strains of species of the genus Marinobacter was ≤30%. On the basis of the aforementioned data, it was concluded that strain YCSA40(T) represents a novel species of the genus Marinobacter, for which the name Marinobacter daqiaonensis sp. nov. is proposed. The type strain is YCSA40(T) (=CGMCC 1.9167(T) =NCCB 100308(T) =LMG 25365(T)).

Diversity and activity of cultivable aerobic planktonic bacteria of a saline Lake located in Sovata, Romania

Aerobic bacterial strains from the salt water of Lake Red (Sovata, Romania) were cultivated. More than half of the 80 strains were G(-) and formed motile straight rods. Only a few strains produced acid from D-glucose and reduced nitrate to nitrite. Optimum NaCl concentration for growth varied between 5 and 15 % in the majority of the strains, so the isolates were regarded moderately halophilic. On the basis of the 16S rRNA gene sequence similarity almost half of the strains were identified as members of genus Halomonas. Other strains belonged to genera Marinobacter, Psychrobacter, Serratia, Morganella (γ-Proteobacteria), Bacillus, Exiguobacterium, Planococcus (Firmicutes), and Arthrobacter, Micrococcus, Microbacterium, and Nesterenkonia (Actinobacteria).

Cold-active halophilic bacteria from the ice-sealed Lake Vida, Antarctica

Lake Vida is a large, permanently ice-covered lake in the Victoria Valley of the McMurdo Dry Valleys, Antarctica and is unique among Dry Valley lakes because it is ice-sealed, with an ice-cover of nearly 19 m. Enrichment cultures of melt-water from Lake Vida 15.9 m ice yielded five pure cultures of aerobic, heterotrophic bacteria. Of these, one strain grew at -8 degrees C and the four others at -4 degrees C. All isolates were either halotolerant or halophilic, with two strains capable of growth at 15% NaCl. Phylogenetic analysis revealed the Lake Vida isolates to be Gammaproteobacteria, related to species of Psychrobacter and Marinobacter. This is the first report of pure cultures of bacteria from Lake Vida, and the isolates displayed a phenotype consistent with life in a cold hypersaline environment.

First evidence of aerobic biodegradation of BTEX compounds by pure cultures of Marinobacter

Marinobacter vinifirmus was shown to degrade toluene as sole carbon and energy source under aerobiosis and at NaCl concentrations in the range 30-150 g/L. Maximum toluene consumption rate, total CO2, and biomass productions were measured in the presence of 60 g/L of NaCl. Under these conditions, 90% of the carbon from toluene was recovered as CO2 and biomass. Maximum specific toluene consumption rate was about 0.12 mgC toluene mgC biomass(-1) h(-1) at NaCl concentrations between 30 and 60 g/L. It decreased to 0.03 mgC toluene mgC biomass(-1) h(-1) at 150 g/L. Besides toluene, M. vinifirmus degraded benzene, ethylbenzene, and p-xylene. Benzene and toluene were utilized to a lesser extent by another Marinobacter sp., Marinobacter hydrocarbonoclasticus.

Bacterial diversity and bioprospecting for cold-active lipases, amylases and proteases, from culturable bacteria of kongsfjorden and Ny-alesund, Svalbard, Arctic

Culturable bacterial diversity of seven marine sediment samples of Kongsfjorden and a sediment and a soil sample from Ny-Alesund, Svalbard, Arctic was studied. The bacterial abundance in the marine sediments of Kongsfjorden varied marginally (0.5 x 10(3)-1.3 x 10(4) cfu/g sediment) and the bacterial number in the two samples collected from the shore of Ny-Alesund also was very similar (0.6 x 10(4) and 3.4 x 10(4), respectively). From the nine samples a total of 103 bacterial isolates were obtained and these isolates could be grouped in to 47 phylotypes based on the 16S rRNA gene sequence belonging to 4 phyla namely Actinobacteria, Bacilli, Bacteroidetes and Proteobacteria. Representatives of the 47 phylotypes varied in their growth temperature range (4-37 degrees C), in their tolerance to NaCl (0.3-2 M NaCl) and growth pH range (2-11). Representatives of 26 phylotypes exhibited amylase and lipase activity either at 5 or 20 degrees C or at both the temperatures. A few of the representatives exhibited amylase and/or lipase activity only at 5 degrees C. None of the phylotypes exhibited protease activity. Most of the phylotypes (38) were pigmented. Fatty acid profile studies indicated that short chain fatty acids, unsaturated fatty acids, branched fatty acids, the cyclic and the cis fatty acids are predominant in the psychrophilic bacteria.

Marinobacter goseongensis sp. nov., from seawater

A Gram-negative marine bacterium, designated strain En6(T), was isolated from seawater of the East Sea of Korea. The organism grew in 1-25 % (w/v) NaCl and at 10-37 degrees C and pH 5.3-9.3, with optimal growth occurring in 4-5 % NaCl and at 25-30 degrees C and pH 7.5. Phylogenetic analysis of the 16S rRNA gene sequence of strain En6(T) placed this bacterium in the clade Marinobacter within the class Gammaproteobacteria. The 16S rRNA gene sequence similarity between strain En6(T) and Marinobacter lipolyticus SM19(T), the most closely related species, was 98.4 %, and the level of DNA-DNA relatedness between the two strains was 22 %. On the basis of the phylogenetic analysis and phenotypic and chemotaxonomic data, strain En6(T) is considered to represent a novel species of the genus Marinobacter. The name Marinobacter goseongensis sp. nov. is proposed, with strain En6(T) (=KCTC 12515(T)=DSM 19471(T)) as the type strain.

Diversity and abundance of nitrate assimilation genes in the northern South china sea

Marine heterotrophic microorganisms that assimilate nitrate play an important role in nitrogen and carbon cycling in the water column. The nasA gene, encoding the nitrate assimilation enzyme, was selected as a functional marker to examine the nitrate assimilation community in the South China Sea (SCS). PCR amplification, restriction fragment length polymorphism (RFLP) screening, and phylogenetic analysis of nasA gene sequences were performed to characterize in situ nitrate assimilatory bacteria. Furthermore, the effects of nutrients and other environmental factors on the genetic heterogeneity of nasA fragments from the SCS were evaluated at the surface in three stations, and at two other depths in one of these stations. The diversity indices and rarefaction curves indicated that the nasA gene was more diverse in offshore waters than in the Pearl River estuary. The phylotype rank abundance curve showed an abundant and unique RFLP pattern in all five libraries, indicating that a high diversity but low abundance of nasA existed in the study areas. Phylogenetic analysis of environmental nasA gene sequences further revealed that the nasA gene fragments came from several common aquatic microbial groups, including the Proteobacteria, Cytophaga-Flavobacteria (CF), and Cyanobacteria. In addition to the direct PCR/sequence analysis of environmental samples, we also cultured a number of nitrate assimilatory bacteria isolated from the field. Comparison of nasA genes from these isolates and from the field samples indicated the existence of horizontal nasA gene transfer. Application of real-time quantitative PCR to these nasA genes revealed a great variation in their abundance at different investigation sites and water depths.

Heterotrophic and autotrophic microbial populations in cold perennial springs of the high arctic

The saline springs of Gypsum Hill in the Canadian high Arctic are a rare example of cold springs originating from deep groundwater and rising to the surface through thick permafrost. The heterotrophic bacteria and autotrophic sulfur-oxidizing bacteria (up to 40% of the total microbial community) isolated from the spring waters and sediments were classified into four phyla (Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria) based on 16S rRNA gene analysis; heterotrophic isolates were primarily psychrotolerant, salt-tolerant, facultative anaerobes. Some of the isolates contained genes for thiosulfate oxidation (soxB) and anoxygenic photosynthesis (pufM), possibly enabling the strains to better compete in these sulfur-rich environments subject to long periods of illumination in the Arctic summer. Although leucine uptake by the spring water microbial community was low, CO(2) uptake was relatively high under dark incubation, reinforcing the idea that primary production by chemoautotrophs is an important process in the springs. The small amounts of hydrocarbons in gases exsolving from the springs (0.38 to 0.51% CH(4)) were compositionally and isotopically consistent with microbial methanogenesis and possible methanotrophy. Anaerobic heterotrophic sulfur oxidation and aerobic autotrophic sulfur oxidation activities were demonstrated in sediment slurries. Overall, our results describe an active microbial community capable of sustainability in an extreme environment that experiences prolonged periods of continuous light or darkness, low temperatures, and moderate salinity, where life seems to rely on chemolithoautotrophy.

Marinobacter guineae sp. nov., a novel moderately halophilic bacterium from an Antarctic environment

Two Gram-negative, cold-adapted, moderately halophilic, aerobic bacteria, designated strains M3B(T) and M3T, were isolated from marine sediment collected from the South Shetland Islands, Antarctica. The organisms were rod-shaped, catalase- and oxidase-positive, and motile by means of polar flagella. These two psychrotolerant strains required Na(+) and grew at NaCl concentrations of 1-15 % and temperatures between 4 and 42 degrees C. 16S rRNA gene sequence analysis placed strains M3B(T) and M3T within the genus Marinobacter. DNA-DNA hybridization experiments between the Antarctic isolate M3B(T) and type strains of phylogenetically related species, namely Marinobacter lipolyticus, Marinobacter flavimaris, Marinobacter sediminum, Marinobacter algicola, Marinobacter maritimus and Marinobacter koreensis, revealed levels of relatedness lower than 32 %. Strain M3T showed 99 % DNA relatedness to strain M3B(T). The DNA G+C contents of M3B(T) and M3T were 57.1 and 57.4 mol%, respectively, and their major isoprenoid quinone was ubiquinone-9. Several phenotypic characteristics, together with data on cellular fatty acid composition, served to differentiate strains M3B(T) and M3T from strains of related Marinobacter species. On the basis of the polyphasic taxonomic evidence presented in this study, it can be concluded that strains M3B(T) and M3T belong to the same genospecies and represent a novel species of the genus Marinobacter, for which the name Marinobacter guineae sp. nov. is proposed. The type strain is M3B(T) (=LMG 24048(T)=CECT 7243(T)).

Marinobacter segnicrescens sp. nov., a moderate halophile isolated from benthic sediment of the South China Sea

A Gram-negative, motile, non-spore-forming and moderately halophilic ellipsoid-shaped marine coccobacillus, designated strain SS011B1-4T, was isolated from benthic sediment of the South China Sea. Optimum growth occurred at 30–37 °C, pH 7.5–8.0 and 4–8 % (w/v) NaCl. Strain SS011B1-4T utilized a variety of organic substrates as sole carbon sources, but did not utilize toluene, n-tetradecane or crude oil. Strain SS011B1-4T had ubiquinone-9 as the major respiratory quinone and C18 : 1 ω9c, C16 : 0 and C12 : 0 3-OH as the predominant fatty acids. The genomic DNA G+C content was 62.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain SS011B1-4T belonged to the genus Marinobacter of the Gammaproteobacteria. The results of the phenotypic, phylogenetic and genomic analyses revealed that strain SS011B1-4T represents a novel species of the genus Marinobacter. The name Marinobacter segnicrescens sp. nov. is therefore proposed, with strain SS011B1-4T (=LMG 23928T=CGMCC 1.6489T) as the type strain.

Analysis of nitrite reductase (nirK and nirS) genes and cultivation reveal depauperate community of denitrifying bacteria in the Black Sea suboxic zone

Chemical profiles of the Black Sea suboxic zone show a distribution of nitrogen species which is traditionally associated with denitrification, i.e. a secondary nitrite maximum associated with nitrate depletion and a N(2) gas peak. To better understand the distribution and diversity of the denitrifier community in the Black Sea suboxic zone, we combined a cultivation approach with cloning and sequencing of PCR-amplified nitrite reductase (nirS and nirK) genes. The Black Sea suboxic zone appears to harbour a homogeneous community of denitrifiers. For nirK, over 94% of the sequences fell into only three distinct phylogenetic clusters, and for nirS, a single closely related sequence type accounted for 91% of the sequences retrieved. Both nirS and nirK genes showed a dramatic shift in community composition at the bottom of the suboxic zone, but overall, nirK-based community composition showed much greater variation across depths compared with the highly uniform distribution of nirS sequences throughout the suboxic zone. The dominant nirK and nirS sequences differed at the amino acid level by at least 17% and 8%, respectively, from their nearest database matches. Denitrifying isolates recovered from the suboxic zone shared 97% 16S rRNA gene sequence similarity with Marinobacter maritimus. Analysis of the recently discovered nirS gene from the anammox bacterium Candidatus'Kuenenia stuttgartiensis' revealed that mismatches with commonly used primers may have prevented the previous detection of this divergent sequence.

Marinobacter salsuginis sp. nov., isolated from the brine–seawater interface of the Shaban Deep, Red Sea

Two moderately halophilic Gram-negative bacteria were isolated from a sample taken from the brine–seawater interface of the Shaban Deep in the Red Sea. Phylogenetic analysis of the 16S rRNA gene sequence showed that these organisms represent a novel species of the genus Marinobacter. Cells of the new isolates formed non-pigmented colonies and were motile by means of a single polar flagellum. Strains SD-14BT and SD-14C grew optimally at 35–37 °C, in 5 % NaCl and at pH 7.5–8.0. The organisms were aerobic, but reduced nitrate to nitrogen under anaerobic conditions. Acid was produced from only a few carbohydrates. Ubiquinone 9 was the major respiratory quinone. The major fatty acids of strains SD-14BT and SD-14C were C16 : 0, C18 : 1 ω9c, summed feature 3 (C16 : 1 ω6c/C16 : 1 ω7c) and C12 : 0 3-OH. The DNA G+C contents were 55.9 and 55.7 mol%, respectively. On the basis of the phylogenetic analyses and physiological and biochemical characteristics, it is proposed that strains SD-14BT and SD-14C represent a novel species of the genus Marinobacter, with the name Marinobacter salsuginis sp. nov. The type strain is strain SD-14BT (=DSM 18347T=LMG 23697T).