The digestive tract sections of the sea cucumber Isostichopus badionotus reveal differences in composition, diversity, and functionality of the gut microbiota

For the first time, this study analyses the composition and diversity of the gut microbiota of Isostichopus badionotus in captivity, using high-throughput 16S rRNA sequencing, and predicts the metagenomic functions of the microbiota. The results revealed a different composition of the gut microbiota for the foregut (FG) and midgut (MG) compared to the hindgut (HG), with a predominance of Proteobacteria, followed by Actinobacteria, Bacteroidetes, and Firmicutes. The FG and MG demonstrated a greater bacterial diversity compared to the HG. In addition, a complex network of interactions was observed at the genus level and identified some strains with probiotic and bioremediation potentials, such as Acinetobacter, Ruegeria, Streptococcus, Lactobacillus, Pseudomonas, Enterobacter, Aeromonas, Rhodopseudomonas, Agarivorans, Bacillus, Enterococcus, Micrococcus, Bifidobacterium, and Shewanella. Predicting metabolic pathways revealed that the bacterial composition in each section of the intestine participates in different physiological processes such as metabolism, genetic and environmental information processing, organismal systems, and cellular processes. Understanding and manipulating microbe--host-environment interactions and their associated functional capacity could substantially contribute to achieving more sustainable aquaculture systems for I. badionotus.

Thiosulfatihalobacter marinus gen. nov. sp. nov., a novel member of the family Roseobacteraceae, isolated from the West Pacific Ocean

Two strains (GL-11-2T and ZH2-Y79) were isolated from the seawater collected from the West Pacific Ocean and the East China Sea, respectively. Cells were Gram-stain-negative, strictly aerobic, non-motile and rod-shaped. Cells grew in the medium containing 0.5–7.5 % NaCl (w/v, optimum, 1.0–3.0 %), at pH 6.0–8.0 (optimum, pH 6.5–7.0) and at 4–40 °C (optimum, 30 °C). H2S production occurred in marine broth supplemented with sodium thiosulphate. The almost-complete 16S rRNA gene sequences of the two isolates were identical, and exhibited the highest similarity to Pseudoruegeria aquimaris JCM 13603T (97.5 %), followed by Ruegeria conchae TW15T (97.2%), Shimia aestuarii DSM 15283T (97.1 %) and Ruegeria lacuscaerulensis ITI-1157T (97.0 %). Phylogenetic analysis revealed that the isolates were affiliated with the family Roseobacteraceae and represented an independent lineage. The sole isoprenoid quinone was ubiquinone 10. The principal fatty acids were summed feature 8 (C18 : 1  ω7c and/or C18 : 1  ω6c) and cyclo-C19 : 0  ω8c. The major polar lipids were phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and diphosphatidylglycerol. The DNA G+C content was 62.3 mol%. The orthologous average nucleotide identity, in silico DNA–DNA hybridization and average amino acid identity values among the genomes of strain GL-11-2T and the reference strains were 73.2–79.0, 20.3–22.5 and 66.0–80.8 %, respectively. Strains GL-11-2ᵀ and ZH2-Y79 possessed complete metabolic pathways for thiosulphate oxidation, dissimilatory nitrate reduction and denitrification. Phylogenetic distinctiveness, chemotaxonomic differences and phenotypic properties revealed that the isolates represent a novel genus and species of the family Roseobacteraceae , belonging to the class Alphaproteobacteria , for which the name Thiosulfatihalobacter marinus gen. nov., sp. nov. (type strain, GL-11–2T=KCTC 82723T=MCCC M20691T) is proposed.

Ruegeria sediminis sp. nov., isolated from tidal flat sediment

A Gram-stain-negative, aerobic, non-motile, rod-shaped bacterial strain, designated CAU 1488^T, was isolated from tidal flat sediment, and its taxonomic position was investigated using a polyphasic approach. The organism grew optimally at a temperature of 30 °C, at pH 7.0-7.5 and in the presence of 0-6 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain CAU 1488^T forms a lineage distinct from Ruegeria marisrubri ZGT 118^T (97.9 %), Ruegeria marina ZH17^T (97.6 %), Ruegeria lacuscaerulensis ITI 1157^T (97.5 %), Ruegeria pomeroyi DSS-3^T (97.1 %), Ruegeria profundi ZGT108^T (97.0 %), Ruegeria intermedia CC-GIMAT-2^T (96.8 %), Ruegeria atlantica CECT 4292^T (96.7 %) and Ruegeria kandeliae J95^T (95.9 %). Genome sequencing revealed that CAU 1488^T had a genome size of 4.23 Mbp and a G+C content of 63.2 mol%. Overall genome related indexes including average nucleotide identity and digital DNA-DNA hybridization values were 75.0-83.0 % and 26.2 %, which are below the cutoffs of 95 and 70 %, respectively, indicating that strain CAU 1488^T represents a distinct species from the members of the genus Ruegeria. The predominant quinone was ubiquinone-10 (Q-10). The major fatty acids were summed feature 8 (C_18 : 1  ω7c/ω6c; 60.7 %) and its polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine and unidentified aminolipids. On the basis of phenotypic, chemotaxonomic and genomic data, strain CAU 1488^T constitutes a novel species of the genus Ruegeria, for which the name Ruegeria sediminis sp. nov. is proposed. The type strain is CAU 1488^T (=KCTC 62996^T=NBRC 113693^T).

Antarcticimicrobium sediminis gen. nov., sp. nov., isolated from Antarctic intertidal sediment, transfer of Ruegeria lutea to Antarcticimicrobium gen. nov. as Antarcticimicrobium luteum comb. nov

A Gram-stain-negative, aerobic, non-flagellated and rod- or ovoid-shaped bacterium, designated as strain S4J41^T, was isolated from Antarctic intertidal sediment. The isolate grew at 0-37 °C and with 0.5-10 % (w/v) NaCl. It reduced nitrate to nitrite and hydrolysed Tween 80 and gelatin. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain S4J41^T constituted a distinct phylogenetic line within the family Rhodobacteraceae and was closely related with some species in the genera Ruegeria, Phaeobacter, Pseudopuniceibacterium, Sulfitobacter, Puniceibacterium and Poseidonocella with 98.6-95.7 % 16S rRNA gene sequence similarities. The major cellular fatty acids were C_16 : 0, summed feature 8 (C_18 : 1  ω7c and/or C_18 : 1  ω6c) and C_18 : 0 and the major polar lipids were phosphatidylglycerol, phosphatidylcholine, diphosphatidylglycerol, phosphatidylethanolamine and one unidentified aminolipid. The sole respiratory quinone was Q-10. The genomic DNA G+C content of strain S4J41^T was 60.3 mol%. Based on the phylogenetic, chemotaxonomic and phenotypic data obtained in this study, strain S4J41^T is considered to represent a novel species in a new genus within the family Rhodobacteraceae, for which the name Antarcticimicrobium sediminis gen. nov., sp. nov. is proposed. The type strain is S4J41^T (=MCCC 1K03508^T=KCTC 62793^T). Moreover, the transfer of Ruegeria lutea Kim et al. 2019 to Antarcticimicrobium gen. nov. as Antarcticimicrobium luteum comb. nov. (type strain 318-1^T=JCM 30927^T=KCTC 72105^T) is also proposed.

Ruegeria lutea sp. nov., isolated from marine sediment, Masan Bay, South Korea

A Gram-stain-negative, non-motile, mesophilic, short rod-shaped, aerobic bacterium designated as 318-1^T was isolated from a marine sediment collected from Masan Bay, South Korea. Strain 318-1^T grew optimally at pH 6-7, at 30 °C and in the presence of 2-3 % (w/v) NaCl, tolerant of up to 8 % (w/v) NaCl, and accumulated poly-β-hydroxybutyrate (PHB). A comparative analysis of 16S rRNA gene sequences revealed that strain 318-1^T formed a distinct phyletic lineage in the genus Ruegeria (family Rhodobacteraceae, class Alphaproteobacteria) and showed high sequence similarity to Ruegeria halocynthiae DSM 27839^T (96.5 %) and Shimia haliotis DSM 28453^T (96.3 %). Comparing the genome sequence of 318-1^T with those of the type strains of seven species of the genus Rugeria and two species of the genus Shimia, the values obtained were below the thresholds with analysis of average nucleotide identities (ANI, 71.6-76.8 %) and in silico DNA-DNA hybridisation, Genome-to-Genome Distance Calculator (GGDC, 18.5-20.6 %). The DNA G+C content was 65.75 mol%. Chemotaxonomic data [predominant quinone ubiquinone Q10; polar lipid profile consisting of major compounds phosphatidylcholine (PC), phosphatidylglycerol (PG), an unidentified aminolipid and an unidentified lipid; major fatty acids summed feature 8 (C_18 : 1ω7c and/or C_18 : 1ω6c)] supported the affiliation of strain 318-1^T to the genus Ruegeria. Genomic, chemotaxonomic, and phenotypic differentiation of strain 318-1^T from the members of the genus Ruegeria support it as a novel species. On the basis of the results in this study, a novel species, Ruegeria lutea sp. nov., is proposed. The type strain is 318-1^T (=JCM 30927^T=KEMB 7306-525^T=KCTC 72105^T).

Biodegradation of crude oil using self-immobilized hydrocarbonoclastic deep sea bacterial consortium

Hydrocarbonoclastic bacterial consortium that utilizes crude oil as carbon and energy source was isolated from marine sediment collected at a depth of 2100 m. Molecular characterization by 16S rRNA gene sequences confirmed that these isolates as Oceanobacillus sp., Nesiotobacter sp., Ruegeria sp., Photobacterium sp., Enterobacter sp., Haererehalobacter sp., Exiguobacterium sp., Acinetobacter sp. and Pseudoalteromonas sp. Self-immobilized consortium degraded more than 85% of total hydrocarbons after 10 days of incubation with 1% (v/v) of crude oil and 0.05% (v/v) of Tween 80 (non-ionic surfactant) at 28 ± 2 °C. The addition of nitrogen and phosphorus sources separately i.e. 0.1% (v/v) of CO (NH₂)₂ or K₂HPO₄ enhanced the hydrocarbon utilization percentage. The pathways of microbial degradation of hydrocarbons were confirmed by FTIR, GC-MS, ¹H and ¹³C NMR spectroscopy analyses. These results demonstrated a novel approach using hydrocarbonoclastic self-immobilized deep sea bacterial consortium for eco-friendly bioremediation.

Proteogenomic Analysis of Epibacterium Mobile BBCC367, a Relevant Marine Bacterium Isolated From the South Pacific Ocean

Epibacterium mobile BBCC367 is a marine bacterium that is common in coastal areas. It belongs to the Roseobacter clade, a widespread group in pelagic marine ecosystems. Species of the Roseobacter clade are regularly used as models to understand the evolution and physiological adaptability of generalist bacteria. E. mobile BBCC367 comprises two chromosomes and two plasmids. We used gel-free shotgun proteomics to assess its protein expression under 16 different conditions, including stress factors such as elevated temperature, nutrient limitation, high metal concentration, and UVB exposure. Comparison of the different conditions allowed us not only to retrieve almost 70% of the predicted proteins, but also to define three main protein assemblages: 584 essential core proteins, 2,144 facultative accessory proteins and 355 specific unique proteins. While the core proteome mainly exhibited proteins involved in essential functions to sustain life such as DNA, amino acids, carbohydrates, cofactors, vitamins and lipids metabolisms, the accessory and unique proteomes revealed a more specific adaptation with the expression of stress-related proteins, such as DNA repair proteins (accessory proteome), transcription regulators and a significant predominance of transporters (unique proteome). Our study provides insights into how E. mobile BBCC367 adapts to environmental changes and copes with diverse stresses.

Ruegeria kandeliae sp. nov., isolated from the rhizosphere soil of a mangrove plant Kandelia candel

A Gram-negative, rod-shaped and motile bacterium, designated strain J95^T, was isolated from the rhizosphere soil of a mangrove plant Kandeliacandel (L.) Druce in Mai Po Nature Reserve, Hong Kong. Growth of strain J95^T was observed at pH 5.0-8.5 (optimum, 6.0-7.0), between 10-40 °C (30-37 °C) and in the presence of 0-9 % (w/v) NaCl (0.5-3 %). Chemotaxonomic analysis showed ubiquinone-10 as the predominant respiratory quinone and C18 : 1ω7c and C19 : 0 cycloω8c as the major fatty acids. The major polar lipids were lipid, aminolipid, phospholipid, phosphatidylcholine, phosphatidylglycerol and phosphatidylethanolamine. The genomic contained a circular chromosome of 5.48 Mb with a DNA G+C content of 65.7 mol%. The genome included 5299 genes. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain J95^T belongs to the genus Ruegeria with highest sequence similarity (96.8 %) to the type strain Ruegeria marina ZH17^T. The combined phenotypic, chemotaxonomic and phylogenetic data suggested that strain J95^T represents a novel species of the genus Ruegeria, for which the name Ruegeria kandeliae sp. nov. is proposed. The type strain is J95^T (=MCCC 1K03284^T=DSM 104293^T).

Ruegeria denitrificans sp. nov., a marine bacterium in the family Rhodobacteraceae with the potential ability for cyanophycin synthesis

Strain CECT 5091^T, an aerobic, marine, Gram-reaction- and Gram-stain-negative, chemoheterotrophic bacterium was isolated from oysters harvested off the Spanish Mediterranean coast. Analysis of the 16S rRNA gene sequence placed the strain within the genus Ruegeria, in the family Rhodobacteraceae, with 16S rRNA gene similarities of 98.7, 98.7 and 98.4 % to Ruegeria conchae, Ruegeria atlanticaand Ruegeria arenilitoris, respectively. Average nucleotide identities (ANI) and in silico DNA-DNA hybridization (DDH) were determined, comparing the genome sequence of CECT 5091^T with those of the type strains of 12 species of the genus Ruegeria: the values obtained were always below the thresholds (95-96 % ANI, 70 % in silico DDH) used to define genomic species, proving that CECT 5091^T represents a novel species of the genus Ruegeria. The strain was slightly halophilic and mesophilic, with optimum growth at 26 °C, pH 7.0 and 3 % salinity, it required sodium and magnesium ions for growth and was able to reduce nitrate to dinitrogen. Carbon sources for growth include some carbohydrates (d-ribose, d-glucose, l-rhamnose, N-acetyl-d-glucosamine) and multiple organic acids and amino acids. The major cellular fatty acid was summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), representing 70 % of the total fatty acids. Carbon monoxide oxidation, cyanophycin synthetic ability and phosphatidylglycerol, diphosphatidylglycerol and phosphatidylcholine production are predicted from genome annotation, while bacteriochlorophyll a production was absent. The DNA G+C content of the genome was 56.7 mol%. We propose the name Ruegeriadenitrificans sp. nov. and strain CECT 5091^T (=5OM10^T=LMG 29896^T) as the type strain for the novel species.

Ruegeria profundi sp. nov. and Ruegeria marisrubri sp. nov., isolated from the brine-seawater interface at Erba Deep in the Red Sea

Two moderately halophilic marine bacterial strains of the family Rhodobacteraceae, designated ZGT108^T and ZGT118^T, were isolated from the brine-seawater interface at Erba Deep in the Red Sea (Saudi Arabia). Cells of both strains were aerobic, rod-shaped, non-motile, and Gram-stain-negative. The sequence similarity of the 16S rRNA genes of strains ZGT108^T and ZGT118^T was 94.9 %. The highest 16S rRNA gene sequence similarity of strain ZGT108^T to its closest relative, Ruegeria conchae JCM 17315^T, was 98.9 %, while the 16S rRNA gene of ZGT118^T was most closely related to that of Ruegeria intermedia LMG 25539^T (97.7 % similarity). The sizes of the draft genomes as presented here are 4 258 055 bp (strain ZGT108^T) and 4 012 109 bp (strain ZGT118^T), and the G+C contents of the draft genomes are 56.68 mol% (ZGT108^T) and 62.94 mol% (ZGT108^T). The combined physiological, biochemical, phylogenetic and genotypic data supported placement of both strains in the genus Ruegeria and indicated that the two strains are distinct from each other as well as from all other members in the genus Ruegeria. This was also confirmed by low DNA-DNA hybridization values (<43.6 %) and low ANI values (<91.8 %) between both strains and the most closely related Ruegeria species. Therefore, we propose two novel species in the genus Ruegeria to accommodate these novel isolates: Ruegeriaprofundi sp. nov. (type strain ZGT108^T=JCM 19518^T=ACCC 19861^T) and Ruegeriamarisrubri sp. nov. (type strain ZGT118^T=JCM 19519^T=ACCC 19862^T).

Phylogenetic structure of bacterial assemblages co-occurring with Ostreopsis cf. ovata bloom

Extensive blooms of the toxic epiphytic/benthic dinoflagellate Ostreopsis cf. ovata are being reported with increasing frequency and spatial distribution in temperate coastal regions including the Mediterranean. These blooms are of human and environmental health concern due to the production of isobaric palytoxin and a wide range of ovatoxins by Ostreopsis cf. ovata. Bacterial-microalgal interactions are important regulators in algal bloom dynamics and potentially toxin dynamics. This study investigated the bacterial assemblages co-occurring with O. cf. ovata (OA) and from ambient seawaters (SW) during the early and peak phases of bloom development in NW Adriatic Sea. Fractions of the bacterial assemblages co-occurring with O. cf. ovata (OA) and more closely associated to the mucilage layer (LA) embedding O. cf. ovata cells were also reported. In total, 14 bacterial phyla were detected by targeted 454 pyrosequencing of the 16S rRNA gene. The dominant bacterial phyla in the OA assemblages were Proteobacteria and Bacteroidetes; while at the class level, Alphaproteobacteria were the most abundant (83 and 66%, relative abundance, early and peak bloom phases), followed by Flavobacteria (7 and 19%, early and peak phases). Actinobacteria and Cyanobacteria were of minor importance (<5% of the relative bacterial abundance each). Gammaproteobacteria showed a notably presence in OA assemblage only at the early phase of the bloom (genus Haliea, 13%). The Alphaproteobacteria were predominately composed by the genera Ruegeria, Jannaschia and Erythrobacter which represented about half of the total phylotypes' contribution of OA at both early and peak phases of the O. cf. ovata bloom, suggesting interactions between this consortium and the microalga. Moreover, the highest contribution of Ruegeria (30% of the total phylotypes) was observed at the early phase of the bloom in LA assemblage. Microbial assemblages associated with the ambient seawaters while being also dominated by Alphaproteobacteria and Flavobacteria were partially distinct from those associated with O. cf. ovata due to the presence of genera almost not retrieved in the latter assemblages.

Lacimonas salitolerans gen. nov., sp. nov., isolated from surface water of a saline lake

A Gram-stain-negative bacterium, strain TS-T30T, was isolated from a saline lake (Lake Tuosu) in Qaidam basin, Qinghai province, China, and its taxonomic position was determined by using a polyphasic approach. Cells were non-spore-forming rods, non-motile, 0.8–1.4 μm wide and 1.9–4.0 μm long. Strain TS-T30T was strictly heterotrophic and aerobic. Catalase- and oxidase-positive. Growth was observed in the presence of 0.5–11.0 % (w/v) NaCl (optimum 3.0 %), and at 10–35 °C (optimum 25 °C) and pH 6.5–10.0 (optimum pH 8.5). Strain TS-T30T contained C18 : 1ω7c as the only predominant fatty acid. The major respiratory quinone was Q-10. The DNA G+C content was 62 mol% (T m). Phylogenetic trees based on 16S rRNA gene sequences showed that strain TS-T30T formed a distinct lineage that was independent of other most closely related genera: Lutimaribacter (95.2–95.9 % 16S rRNA gene sequence similarities), Poseidonocella (95.4 %), Ruegeria (92.8–94.9 %), Marivita (93.6–94.9 %), Seohaeicola (94.7 %), Sediminimonas (94.7 %), Shimia (93.9–94.7 %), Oceanicola (92.6–94.5 %) and Roseicyclus (94.5 %). The major polar lipids were phosphatidylglycerol, one unidentified phospholipid and an unknown aminolipid; phosphatidylcholine was not detected. These data demonstrated that strain TS-T30T represents a novel species of a new genus in the family Rhodobacteraceae, for which the name Lacimonas salitolerans gen. nov., sp. nov. is proposed. The type strain of the type species is TS-T30T ( = CGMCC 1.12477T = NBRC 110969T).

Cribrihabitans marinus gen. nov., sp. nov., isolated from a biological filter in a marine recirculating aquaculture system

A Gram-negative bacterium, strain CZ-AM5T, was isolated from an aerated biological filter in a marine recirculating aquaculture system in Tianjin, China. Its taxonomic position was investigated by using a polyphasic approach. Cells of strain CZ-AM5T were non-spore-forming rods, 0.5–0.8 µm wide and 1.2–2.0 µm long, and motile by means of one or two polar or lateral flagella. Strain CZ-AM5T was strictly aerobic, heterotrophic, oxidase-negative and catalase-positive. Growth occurred at 15–40 °C (optimum, 30–35 °C), at pH 6.5–10.5 (optimum, pH 7.0–7.5) and in the presence of 0–12.0 % (w/v) NaCl (optimum, 4.0 %). The predominant fatty acid was C18 : 1ω7c (80.3 %). Ubiquinone 10 (Q-10) was the sole respiratory quinone. The polar lipids were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, an unknown aminolipid, an unknown phospholipid and three unknown lipids. The DNA G+C content was 60.4 mol%. Strain CZ-AM5T showed the highest 16S rRNA gene sequence similarity (96.5 %) to Phaeobacter caeruleus LMG 24369T; it exhibited 16S rRNA gene sequence similarity of 95.0–96.5, 95.2–96.3, 96.2, 94.6–95.7 and 94.8–95.8 % to members of the genera Phaeobacter , Ruegeria , Citreimonas , Leisingera and Donghicola , respectively. However, phylogenetic trees based on 16S rRNA gene sequences showed that strain CZ-AM5T did not join any of the above genera, but formed a distinct lineage in the trees. On the basis of phenotypic, chemotaxonomic and phylogenetic analyses, strain CZ-AM5T is considered to represent a novel genus and species of the family Rhodobacteraceae , for which the name Cribrihabitans marinus gen. nov., sp. nov. is proposed. The type strain of Cribrihabitans marinus is CZ-AM5T ( = CGMCC 1.13219T = JCM 19401T).

Ruegeria meonggei sp. nov., an alphaproteobacterium isolated from ascidian Halocynthia roretzi

A Gram-negative, strictly aerobic, non-flagellated and rod-shaped bacterial strain, designated MA-E2-3(T), was isolated from an ascidian (Halocynthia roretzi) collected from the South Sea, South Korea. Strain MA-E2-3(T) was found to grow optimally at 30 °C, at pH 7.0-8.0 and in the presence of 2.0-3.0 % (w/v) NaCl. A neighbour-joining phylogenetic tree based on 16S rRNA gene sequences revealed that strain MA-E2-3(T) fell within the clade comprising Ruegeria species, clustering consistently with the type strain of Ruegeria halocynthiae, with which it exhibited 98.2 % sequence similarity. Sequence similarities to the type strains of the other recognized Ruegeria species were 94.7-97.7 %. Strain MA-E2-3(T) was found to contain Q-10 as the predominant ubiquinone and C18:1 ω7c as the predominant fatty acid. The major polar lipids of strain MA-E2-3(T) were identified as phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, one unidentified aminolipid and one unidentified lipid. The DNA G+C content of strain MA-E2-3(T) was determined to be 58.0 mol%. Mean DNA-DNA relatedness values between strain MA-E2-3(T) and the type strains of four phylogenetically closely related Ruegeria species were in the range of 13-23 %. The differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, revealed that strain MA-E2-3(T) is separated from other Ruegeria species. On the basis of the data presented, strain MA-E2-3(T) (=KCTC 32450(T) = CECT 8411(T)) represents a novel species of the genus Ruegeria, for which the name Ruegeria meonggei sp. nov. is proposed.

Ruegeria intermedia sp. nov., a moderately thermophilic bacterium isolated from a coastal hot spring

A cream-coloured, Gram-negative, aerobic, non-motile moderately thermophilic, rod-to-irregular-shaped bacterium, CC-GIMAT-2T, was isolated from a coastal hot spring of Green Island (Lutao), located off Taituang, Taiwan, on marine agar 2216. The 16S rRNA gene sequence analysis and subsequent comparisons showed that it was placed into the genus Ruegeria with 97.4 % similarity to Ruegeria lacuscaerulensis ITI-1157T, and a lower sequence similarity to all other species of the genus Ruegeria . Reconstruction of phylogenetic trees indicated that strain CC-GIMAT-2T clustered within the genus Ruegeria . Robust tree topology for the genus Ruegeria including the new strain was only obtained by including all Rhodobacteraceae type strains but not if the analysis was limited to few selected taxa. The quinone system contained exclusively ubiquinone Q-10 and the fatty acid profile consisted mainly of C18 : 1ω7c, 11-methyl C18 : 1ω7c and C12 : 0 3-OH. The predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol and an unidentified aminolipid. Other lipids were detected in moderate to minor amounts. The characteristic feature of the polyamine pattern was the predominant triamine spermidine. On the basis of the 16S rRNA gene sequence analysis and of the chemotaxonomic and physiological data, strain CC-GIMAT-2T represents a novel species of the genus Ruegeria , for which the name Ruegeria intermedia sp. nov. is proposed. The type strain is CC-GIMAT-2T ( = CCUG 59209T = LMG 25539T = CCM 7758T).