Marinomonas rhodophyticola sp. nov. and Marinomonas phaeophyticola sp. nov., isolated from marine algae

Two Gram-stain-negative, facultatively aerobic, and motile rod bacteria, designated as strains KJ51-3T and 15G1-11T, were isolated from marine algae collected in the Republic of Korea. Both strains exhibited catalase- and oxidase-positive activities. Optimum growth conditions for strain KJ51-3T were observed at 30 °C and pH 6.0-8.0, with 1.0-7.0 % (w/v) NaCl, whereas strain 15G1-11T exhibited optimal growth at 30 °C, pH 7.0, and 1.0-5.0 % NaCl. Major fatty acids detected in both strains included C16 : 0, C10 : 0 3-OH and summed features 3 (C16 : 1  ω7c and/or C16 : 1  ω6c) and 8 (C18 : 1  ω7c and/or C18 : 1  ω6c). As for polar lipids, strain KJ51-3T contained phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol, and two unidentified phospholipids, whereas strain 15G1-11T had PE, PG, and an unidentified aminolipid. Ubiquinone-8 was the predominant respiratory quinone in both strains, with minor detection of ubiquinone-9 in strain KJ51-3T. The genomic DNA G+C contents were 44.0 mol% for strain KJ51-3T and 40.5 mol% for strain 15G1-11T. Phylogenetic analyses based on both 16S rRNA gene and genome sequences placed strains KJ51-3T and 15G1-11T into distinct lineages within the genus Marinomonas, most closely related to Marinomonas arctica 328T (98.6 %) and Marinomonas algicola SM1966T (98.3 %), respectively. Strains KJ51-3T and 15G1-11T exhibited a 94.6 % 16S rRNA gene sequence similarity and a 70.7 % average nucleotide identity (ANI), with ANI values of 91.9 and 79.3 % between them and M. arctica 328T and M. algicola SM1966T, respectively, indicating that they represent novel species. In summary, based on their phenotypic, chemotaxonomic, and phylogenetic properties, strains KJ51-3T and 15G1-11T are proposed to represent novel species within the genus Marinomonas, for which the names Marinomonas rhodophyticola sp. nov. (KJ51-3T=KACC 22756T=JCM 35591T) and Marinomonas phaeophyticola sp. nov. (15G1-11T=KACC 22593T=JCM 35412T) are respectively proposed.

Marinomonas mediterranea synthesizes an R-type bacteriocin

Prophages integrated into bacterial genomes can become cryptic or defective prophages, which may evolve to provide various traits to bacterial cells. Previous research on Marinomonas mediterranea MMB-1 demonstrated the production of defective particles. In this study, an analysis of the genomes of three different strains (MMB-1, MMB-2, and MMB-3) revealed the presence of a region named MEDPRO1, spanning approximately 52 kb, coding for a defective prophage in strains MMB-1 and MMB-2. This prophage seems to have been lost in strain MMB-3, possibly due to the presence of spacers recognizing this region in an I-F CRISPR array in this strain. However, all three strains produce remarkably similar defective particles. Using strain MMB-1 as a model, mass spectrometry analyses indicated that the structural proteins of the defective particles are encoded by a second defective prophage situated within the MEDPRO2 region, spanning approximately 13 kb. This finding was further validated through the deletion of this second defective prophage. Genomic region analyses and the detection of antimicrobial activity of the defective prophage against other Marinomonas species suggest that it is an R-type bacteriocin. Marinomonas mediterranea synthesizes antimicrobial proteins with lysine oxidase activity, and the synthesis of an R-type bacteriocin constitutes an additional mechanism in microbial competition for the colonization of habitats such as the surface of marine plants.IMPORTANCEThe interactions between bacterial strains inhabiting the same environment determine the final composition of the microbiome. In this study, it is shown that some extracellular defective phage particles previously observed in Marinomonas mediterranea are in fact R-type bacteriocins showing antimicrobial activity against other Marinomonas strains. The operon coding for the R-type bacteriocin has been identified.

Adaptation Potential of Three Psychrotolerant Aquatic Bacteria in the Pan-Okhotsk Region

The Pan-Okhotsk region, which is part of the western North Pacific Ocean, is famous for its active volcanoes, which are part of the Pacific Ring of Fire and that enrich the surrounding waters with essential chemicals. Therefore, this region, including the Sea of Okhotsk and the Sea of Japan, is characterized by rich biota. Bacterioplankton plays a significant part in biological communities and is an indicator of ecosystem function. Analyzing the adaptability of three representatives of the microbiota of the Pan-Okhotsk region was the goal of our investigation. Marinomonas primoryensis KMM3633T (MP), Yersinia ruckeri KMM821 (YR), and Yersinia pseudotuberculosis 598 (YP) from the G.B. Elyakov Pacific Institute of Bioorganic Chemistry were studied by means of genomic and bioinformatic methods. The list of membrane translocator proteins, metabolism pathways, and cold shock and antifreeze proteins that were revealed in the genome of MP characterized this bacterium as being adaptable to free living in marine conditions, even at winter temperatures. The genomic potential of YR and YP makes not only survival in the environment of the Pan-Okhotsk region but also pathogenesis in eukaryotic organisms possible. The data obtained will serve as a basis for further ecosystem monitoring with the help of microbiota research.

Dissolved organic matter production from herder application and in-situ burning of crude oil at high latitudes: Bioavailable molecular composition patterns and microbial community diversity effects

Chemical herders and in-situ burning (ISB) are designed to mitigate the effects that oil spills may have on the high latitude marine environment. Little information exists on the water solubilization of petroleum residues stemming from chemically herded ISB and whether these bioavailable compounds have measurable impacts on marine biota. In this experiment, we investigated the effects of Siltech OP40 and crude oil ISB on a) petroleum-derived dissolved organic matter (DOM_HC) composition and b) seawater microbial community diversity over 28 days at 4 °C in aquarium-scale mesocosms. Ultra-high resolution mass spectrometry and fluorescence spectroscopy revealed increases in aromaticity over time, with ISB and ISB+OP40 samples having higher % aromatic classes in the initial incubation periods. ISB+OP40 contained a nearly 12-fold increase in the number of DOM_HC formulae relative to those before ISB. 16S rRNA gene sequencing identified differences in microbial alpha diversity between seawater, ISB, OP40, and ISB+OP40. Microbial betadiversity shifts were observed that correlated strongly with aromatic/condensed relative abundance and incubation time. Proteobacteria, specifically from the genera Marinomonas and Perlucidibaca experienced -22 and +24 log₂-fold changes in ISB+OP40 vs. seawater, respectively. These findings provide an important opportunity to advance our understanding of chemical herders and ISB in the high latitude marine environment.

Marinomonas vulgaris sp. nov., a marine bacterium isolated from seawater in a coastal intertidal zone of Zhoushan island

A Marinomonas-like, Gram-stain-negative, strictly aerobic and rod to ovoid-shaped bacterium, designated as strain A79^T, was isolated from the seawater mixtures of oyster shells and brown algae in a coastal intertidal zone of Zhoushan, China. The strain was positive for oxidase and catalase. Colonies grown on marine agar for 48 h were round, milky white, smooth and moist with the diameter of 2-3 mm. Growth was observed at 15-30 °C (optimum, 25℃), pH 5.5-9.5 (optimum, pH 8.5) and with 0.5-8% (w/v) NaCl (optimum, 2-2.5%). The G + C content based on the genome sequence was 46.0%. The only respiratory quinone was Q-8. The main polar lipids contained phosphatidylglycerol, phosphatidylethanolamine, unidentified glycolipids, unidentified phospholipid and three unidentified lipids. The major fatty acids (> 10%) were C_16:0, Summed feature 3 (comprising C_16:1 ω6c and/or C_16:1 ω7c) and summed feature 8 (comprising C_18:1 ω6c and/or C_18:1 ω7c). The 16S rRNA gene sequence similarity between strain A79^T and Marinomonas pollencensis IVIA-Po-185^T was 97.4%, the similarities with other type strains of the genus Marinomonas were 93.8-96.7%. Based on the results, Marinomonas vulgaris sp. nov. was proposed as a novel species. The type strain is A79^T (= MCCC 1K05799^T = KCTC 82519^T = JCM 34473^T).

Statistical Optimisation and Kinetic Studies of Molybdenum Reduction Using a Psychrotolerant Marine Bacteria Isolated from Antarctica

The extensive industrial use of the heavy metal molybdenum (Mo) has led to an emerging global pollution with its traces that can even be found in Antarctica. In response, a reduction process that transforms hexamolybdate (Mo6+) to a less toxic compound, Mo-blue, using microorganisms provides a sustainable remediation approach. The aim of this study was to investigate the reduction of Mo by a psychrotolerant Antarctic marine bacterium, Marinomonas sp. strain AQ5-A9. Mo reduction was optimised using One-Factor-At-a-Time (OFAT) and Response Surface Methodology (RSM). Subsequently, Mo reduction kinetics were further studied. OFAT results showed that maximum Mo reduction occurred in culture media conditions of pH 6.0 and 50 ppt salinity at 15 °C, with initial sucrose, nitrogen and molybdate concentrations of 2.0%, 3.0 g/L and 10 mM, respectively. Further optimization using RSM identified improved optimum conditions of pH 6.0 and 47 ppt salinity at 16 °C, with initial sucrose, nitrogen and molybdate concentrations of 1.8%, 2.25 g/L and 16 mM, respectively. Investigation of the kinetics of Mo reduction revealed Aiba as the best-fitting model. The calculated Aiba coefficient of maximum Mo reduction rate (µmax) was 0.067 h−1. The data obtained support the potential use of marine bacteria in the bioremediation of Mo.

Marinomonas algicola sp. nov. and Marinomonas colpomeniae sp. nov., isolated from marine macroalgae

Two Gram-stain-negative, aerobic, rod-shaped bacteria, polar flagellated, designated strains SM2066^T and SM1966^T, were respectively isolated from the surfaces of Colpomenia sinuosa and Ulva pertusa macroalgae collected off the coastal areas of Rongcheng, PR China. Strain SM2066^T grew at 8-37 °C and with 0.5-7.0 % (w/v) NaCl, while strain SM1966^T grew at 5-30 °C and with 0.5-8.5% (w/v) NaCl. Both of them reduced nitrate to nitrite and required Na⁺ for growth but neither of them hydrolysed starch and DNA. Phylogenetic analysis based on 16S rRNA gene and single-copy orthologous cluster sequences revealed that both strains SM2066^T and SM1966^T were affiliated with the genus Marinomonas but formed distinct phylogenetic branches from known Marinomonas species, respectively sharing the highest 16S rRNA gene sequence similarities with type strains of Marinomonas ushuaiensis (97.9 %) and Marinomonas blandensis (96.7 %). The digital DNA-DNA hybridization and average nucleotide identity values between strains SM2066^T and SM1966^T and type strains of closely related Marinomonas species were all below 22.9 and 79.9 mol%, respectively. The major fatty acids of the two strains were summed feature 3 (C_16 : 1  ω6c/C_16 : 1  ω7c), summed feature 8 (C_18 : 1  ω7c) and C_16 : 0, with their predominant polar lipids being phosphatidylethanolamine and phosphatidylglycerol, and their sole respiratory quinone being Q-8. The genomic DNA G+C contents of strains SM2066^T and SM1966^T determined from genomic sequences were 40.3 and 41.6 mol%, respectively. On the basis of the polyphasic evidence presented in this study, strains SM2066^T and SM1966^T are considered to represent two novel species within the genus Marinomonas, for which the names Marinomonas colpomeniae sp. nov. and Marinomonas algicola sp. nov. are proposed. The type strains are SM2066^T (=MCCC 1K04390^T= KCTC 82372^T) and SM1966^T (=MCCC 1K04387^T= KCTC 72848^T), respectively.

Complete genome sequence of Marinomonas arctica BSI20414, a giant antifreeze protein-producing bacterium isolated from Arctic sea ice

Sea ice in the polar oceans is a dynamic and challenging environment for life to survive, with extreme gradients of temperature, salinity and nutrients etc., as well as formation of ice crystals. Bacteria surviving in sea ice attract broad attention from academia and industry, due to fascinating mechanisms for adaptation. Here we described the complete genome sequence of Marinomonas arctica BSI20414, isolated from Arctic sea ice. The strain tolerated high salinity and low temperature. Genetic features commonly related to adaptation to oxidative stress, osmotic stress and cold stress were detected in the genome. In addition, a large adhesion protein containing a putative antifreeze protein (AFP) domain was detected in the genome, similar with the giant AFP MpIBP from M. primoryensis. The presence of the putative AFP could facilitate M. arctica BSI20414 to bind to sea ice for favorable conditions and protect it from freezing. The genome sequence and the AFP reported here can provide insights into adaptation to sea ice and can be explored further for biotechnological applications.

Marinomonas profundi sp. nov., isolated from deep seawater of the Mariana Trench

A Gram-stain-negative, aerobic, polarly flagellated, straight or curved rod-shaped bacterium, designated strain M1K-6^T, was isolated from deep seawater samples collected from the Mariana Trench. The strain grew at -4 to 37 °C (optimum, 25-30 °C), at pH 5.5-10.0 (optimum, pH 7.0) and with 0.5-14.0  % (w/v) NaCl (optimum, 2.0 %). It did not reduce nitrate to nitrite nor hydrolyse gelatin or starch. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain M1K-6^T was affiliated with the genus Marinomonas, sharing 93.1-97.0  % sequence similarity with the type strains of recognized Marinomonas species. The major cellular fatty acids were summed feature 3 (C_16 : 1 ω6c/C_16 : 1 ω7c), summed feature 8 (C_18 : 1 ω7c/C_18 : 1 ω6c), C_16 : 0, C_10 : 0 3-OH and C_18 : 0. The predominant respiratory quinone was ubiquinone-8. Polar lipids of strain M1K-6^T included phosphatidylethanolamine, phosphatidylglycerol and two unidentified lipids. The genomic G+C content of strain M1K-6^T was 46.0 mol%. Based on data from the present polyphasic study, strain M1K-6^T was considered to represent a novel species within the genus Marinomonas, for which the name Marinomonas profundi sp. nov. is proposed. The type strain is M1K-6^T (=KCTC 72501^T=MCCC 1K03890^T).

Horizontal gene transfer and silver nanoparticles production in a new Marinomonas strain isolated from the Antarctic psychrophilic ciliate Euplotes focardii

We isolated a novel bacterial strain from a prokaryotic consortium associated to the psychrophilic marine ciliate Euplotes focardii, endemic of the Antarctic coastal seawater. The 16S rDNA sequencing and the phylogenetic analysis revealed the close evolutionary relationship to the Antarctic marine bacterium Marinomonas sp. BSw10506 and the sub antarctic Marinomonas polaris. We named this new strain Marinomonas sp. ef1. The optimal growth temperature in LB medium was 22 °C. Whole genome sequencing and analysis showed a reduced gene loss limited to regions encoding for transposases. Additionally, five genomic islands, e.g. DNA fragments that facilitate horizontal gene transfer phenomena, were identified. Two open reading frames predicted from the genomic islands coded for enzymes belonging to the Nitro-FMN-reductase superfamily. One of these, the putative NAD(P)H nitroreductase YfkO, has been reported to be involved in the bioreduction of silver (Ag) ions and the production of silver nanoparticles (AgNPs). After the Marinomonas sp. ef1 biomass incubation with 1 mM of AgNO₃ at 22 °C, we obtained AgNPs within 24 h. The AgNPs were relatively small in size (50 nm) and had a strong antimicrobial activity against twelve common nosocomial pathogenic microorganisms including Staphylococcus aureus and two Candida strains. To our knowledge, this is the first report of AgNPs biosynthesis by a Marinomonas strain. This biosynthesis may play a dual role in detoxification from silver nitrate and protection from pathogens for the bacterium and potentially for the associated ciliate. Biosynthetic AgNPs also represent a promising alternative to conventional antibiotics against common pathogens.

Marinomonas epiphytica sp. nov., isolated from a marine intertidal macroalga

A novel Gram-stain-negative, aerobic marine bacterial strain, SAB-3T, was isolated from brown macroalgae (Dictyota sp.) growing in the Arabian sea, Goa, India. The strain grew optimally at 30 °C, with 2.0-4.0 % (w/v) NaCl and at pH 7.0 on marine agar medium. Strain SAB-3T was unable to hydrolyse aesculin and did not grow in the presence of rifamycin but showed resistance to antibiotics such as cefadroxil and co-trimoxazole. The major fatty acids were summed feature 8 (C18 : 1ω7c/C18 : 1ω6c), summed feature 3 (C16 : 1ω7c/C16 : 1ω6c) and C16 : 0, and Q-8 was the major ubiquinone. The major polar lipids were phosphatidylglycerol and phosphatidylethanolamine. The DNA G+C content was 41.0 mol%. 16S rRNA gene sequencing and phylogenetic analysis indicated that the strain was a member of the genus Marinomonas with Marinomonas aquiplantarum IVIA-Po-159T (97.6 % similarity), Marinomonas posidonica IVIA-Po-181T (97.5 %) and Marinomonas dokdonensis DSM 17202T (97.4 %) as the closest relatives. Whole genome relatedness determined through DNA-DNA hybridization revealed values of 40-50 % (below the 70 % threshold recommended for species delineation) with the above three species, thus confirming it as representing a distinct and novel species of the genus Marinomonas for which the name Marinomonas epiphytica sp. nov. is proposed. The type strain is SAB-3T (=JCM 31365T=KCTC 52293T=MTCC 12569T).

Marinomonas blandensis sp. nov., a novel marine gammaproteobacterium

A novel Gram-staining-negative, chemoorganotrophic, moderately halophilic, strictly aerobic bacterium, strain MED121T, was isolated from a seawater sample collected at the Blanes Bay Microbial Observatory in the north-western Mediterranean Sea. Analysis of its 16S rRNA gene sequence, retrieved from the whole-genome sequence, showed that this bacterium was most closely related to Marinomonas dokdonensis and other Marinomonas species (96.3 and 93.3-95.7 % sequence similarities, respectively), within the family Oceanospirillaceae. Strain MED121T was included into a whole-genome sequencing study and, subsequently, it was characterized using a polyphasic taxonomic approach. It was found to be oxidase and catalase positive, its cells are cocci to short rods, it does not ferment carbohydrates and does not reduce nitrate to nitrite or gas and it requires at least 2.5 % (w/v) marine salts and tolerates up to 7 % (w/v) salts. Its major cellular fatty acids in order of abundance are C16 : 1ω7c/C16 : 1ω6c, C18 : 1ω7c, C16 : 0 and C10 : 0 3-OH. Its genome had an approximate length of 5.1 million bases and a DNA G+C content equal to 40.9 mol%. Analysis of the annotated genes reveals the capacity for the synthesis of ubiquinone 8 (Q8) and the polar lipids phosphatidylglycerol and phosphatidylethanolamine, in agreement with other members of the genus. All the data collected supported the creation of a novel species to accommodate this bacterium, for which the name Marinomonas blandensis sp. nov. is proposed. The type strain is MED121T (=CECT 7076T=LMG 29722T).

Complete genome sequence of Marinomonas bacteriophage P12026

Members of the genus Marinomonas in the Gammaproteobacteria are broadly distributed in marine environments where they could be infected by bacteriophages. Here we report the genome sequence of bacteriophage P12026 that can lytically infect bacterial strain IMCC12026, a member of the genus Marinomonas. To our knowledge, this is the first genome sequence of a lytic bacteriophage infecting the genus Marinomonas.

Marinomonas hwangdonensis sp. nov., isolated from seawater

A Gram-negative, motile, rod-shaped bacterial strain, designated HDW-15T, was isolated from seawater of the Yellow Sea, Korea, and subjected to a polyphasic taxonomic study. Strain HDW-15T grew optimally at pH 7.0–8.0, at 25 °C and in the presence of 2 % (w/v) NaCl. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain HDW-15T fell within the clade comprising Marinomonas species, joining the type strain of Marinomonas arctica , with which it exhibited highest 16S rRNA gene sequence similarity (97.7 %). The 16S rRNA gene sequence similarity values between strain HDW-15T and the type strains of other Marinomonas species were in the range 93.7–97.2 %. Mean DNA–DNA relatedness values between strain HDW-15T and the type strains of M. arctica , Marinomonas polaris and Marinomonas pontica were 5.0–9.9 %. The DNA G+C content of the isolate was 48.7 mol%. Strain HDW-15T contained Q-8 as the predominant ubiquinone and C18 : 1ω7c, summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH) and C16 : 0 as the major fatty acids. The major polar lipids found in strain HDW-15T were phosphatidylglycerol and phosphatidylethanolamine. Differential phenotypic properties, together with phylogenetic and genetic distinctiveness, showed that strain HDW-15T can be differentiated from other Marinomonas species. On the basis of the data presented, strain HDW-15T is considered to represent a novel species of the genus Marinomonas , for which the name Marinomonas hwangdonensis sp. nov. is proposed. The type strain is HDW-15T ( = KCTC 23661T = CCUG 61321T).

Enrichment of arsenic transforming and resistant heterotrophic bacteria from sediments of two salt lakes in Northern Chile

Microbial populations are involved in the arsenic biogeochemical cycle in catalyzing arsenic transformations and playing indirect roles. To investigate which ecotypes among the diverse microbial communities could have a role in cycling arsenic in salt lakes in Northern Chile and to obtain clues to facilitate their isolation in pure culture, sediment samples from Salar de Ascotán and Salar de Atacama were cultured in diluted LB medium amended with NaCl and arsenic, at different incubation conditions. The samples and the cultures were analyzed by nucleic acid extraction, fingerprinting analysis, and sequencing. Microbial reduction of As was evidenced in all the enrichments carried out in anaerobiosis. The results revealed that the incubation factors were more important for determining the microbial community structure than arsenic species and concentrations. The predominant microorganisms in enrichments from both sediments belonged to the Firmicutes and Proteobacteria phyla, but most of the bacterial ecotypes were confined to only one system. The occurrence of an active arsenic biogeochemical cycle was suggested in the system with the highest arsenic content that included populations compatible with microorganisms able to transform arsenic for energy conservation, accumulate arsenic, produce H(2), H(2)S and acetic acid (potential sources of electrons for arsenic reduction) and tolerate high arsenic levels.

Marinomonas alcarazii sp. nov., M. rhizomae sp. nov., M. foliarum sp. nov., M. posidonica sp. nov. and M. aquiplantarum sp. nov., isolated from the microbiota of the seagrass Posidonia oceanica

Five novel Gram-reaction-negative aerobic marine bacterial strains with DNA G+C contents <50 mol% were isolated from the seagrass Posidonia oceanica. 16S rRNA sequence analysis indicated that they belonged to the genus Marinomonas. Major fatty acid compositions, comprising C10 : 0 3-OH, C16 : 0, C16 : 1ω7c and C18 : 1ω7c, supported the affiliation of these strains to the genus Marinomonas. Strains IVIA-Po-14bT, IVIA-Po-145T and IVIA-Po-155T were closely related to Marinomonas pontica 46-16T, according to phylogenetic analysis. However, DNA–DNA hybridization values <35 % among these strains revealed that they represented different species. Further differences in the phenotypes and minor fatty acid compositions were also found among the strains. Another two strains, designated IVIA-Po-181T and IVIA-Po-159T, were found to be closely related to M. dokdonensis DSW10-10T but DNA–DNA relatedness levels <40 % in pairwise comparisons, as well as some additional differences in phenotypes and fatty acid compositions supported the creation of two novel species. Accordingly, strains IVIA-Po-14bT ( = CECT 7730T  = NCIMB 14671T), IVIA-Po-145T ( = CECT 7377T  = NCIMB 14431T), IVIA-Po-155T ( = CECT 7731T  = NCIMB 14672T), IVIA-Po-181T ( = CECT 7376T  = NCIMB 14433T) and IVIA-Po-159T ( = CECT 7732T  = NCIMB 14673T) represent novel species, for which the names Marinomonas alcarazii sp. nov., Marinomonas rhizomae sp. nov., Marinomonas foliarum sp. nov., Marinomonas posidonica sp. nov. and Marinomonas aquiplantarum sp. nov. are proposed, respectively.

Marinomonas brasilensis sp. nov., isolated from the coral Mussismilia hispida, and reclassification of Marinomonas basaltis as a later heterotypic synonym of Marinomonas communis

A Gram-negative, aerobic bacterium, designated strain R-40503T, was isolated from mucus of the reef-builder coral Mussismilia hispida, located in the São Sebastião Channel, São Paulo, Brazil. Phylogenetic analyses revealed that strain R-40503T belongs to the genus Marinomonas. The 16S rRNA gene sequence similarity of R-40503T was above 97 % with the type strains of Marinomonas vaga, M. basaltis, M. communis and M. pontica, and below 97 % with type strains of the other Marinomonas species. Strain R-40503T showed less than 35 % DNA–DNA hybridization (DDH) with the type strains of the phylogenetically closest Marinomonas species, demonstrating that it should be classified into a novel species. Amplified fragment length polymorphism (AFLP), chemotaxonomic and phenotypic analyses provided further evidence for the proposal of a novel species. Concurrently, a close genomic relationship between M. basaltis and M. communis was observed. The type strains of these two species showed 78 % DDH and 63 % AFLP pattern similarity. Their phenotypic features were very similar, and their DNA G+C contents were identical (46.3 mol%). Collectively, these data demonstrate unambiguously that Marinomonas basaltis is a later heterotypic synonym of Marinomonas communis. Several phenotypic features can be used to discriminate between Marinomonas species. The novel strain R-40503T is clearly distinguishable from its neighbours. For instance, it shows oxidase and urease activity, utilizes l-asparagine and has the fatty acid C12 : 1 3-OH but lacks C10 : 0 and C12 : 0. The name Marinomonas brasilensis sp. nov. is proposed, with the type strain R-40503T ( = R-278T  = LMG 25434T  = CAIM 1459T). The DNA G+C content of strain R-40503T is 46.5 mol%.