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PubMed2006

Yangia pacifica gen. nov., sp. nov., a novel member of the Roseobacter clade from coastal sediment of the East China Sea.

An aerobic, Gram-negative bacterial isolate, strain DX5-10T, was isolated from coastal sediment of the East China Sea. The taxonomy of strain DX5-10T was studied by phenotypic and phylogenetic methods. Strain DX5-10T was motile, formed faint-yellowish colonies and was positive for catalase reaction and weakly positive for oxidase reaction. The nearly complete 16S rRNA gene of strain DX5-10T was obtained and sequence analysis indicated that strain DX5-10T represented an independent lineage within the Roseobacter clade of Alphaproteobacteria. Strain DX5-10T was phylogenetically related to members of the genera Roseobacter, Loktanella, Roseisalinus, Silicibacter, Antarctobacter, Sulfitobacter, Salipiger, Ruegeria and Roseivivax, and the sequence identities among them were less than 95.0%. The predominant respiratory ubiquinone of strain DX5-10T was Q-10 and the DNA G + C content of strain DX5-10T was 63.3 mol%. Therefore, strain DX5-10T represents a novel species of a novel genus, for which the name Yangia pacifica gen. nov., sp. nov. is proposed, with the type strain DX5-10T (= CGMCC 1.3455T = JCM 12573T).

Bacteriochlorophyll A↗
PubMed2006

Citreimonas salinaria gen. nov., sp. nov., a member of the Roseobacter clade isolated from a solar saltern.

A lemon-shaped marine bacterium, strain CL-SP20(T), isolated from hypersaline water from a solar saltern in Korea, was characterized in terms of its physiological and biochemical features, its fatty acid profile and its phylogenetic position based on 16S rRNA gene sequences. Analysis of the 16S rRNA gene sequence revealed a clear affiliation with the Roseobacter lineage (91.0-96.3 % similarity) of the family Rhodobacteraceae. However, strain CL-SP20(T) did not form a robust clade with any species of the Roseobacter clade, forming a distinct subline. Strain CL-SP20(T) is non-motile and forms beige colonies on marine agar. The strain is able to grow with sea salts at concentrations in the range 1-10 %, with optimal growth between 5 and 6 %. It grows at temperatures in the range 15-40 degrees C and at pH 6-10. The strain cannot oxidize thiosulfate. The fatty acids are dominated by 18 : 1omega7c (54.3 %) and 19 : 0 cyclo omega8c (20.4 %). The DNA G+C content is 67.3 mol%. According to the physiological data, fatty acid composition and phylogenetic analysis of the 16S rRNA gene sequence, strain CL-SP20(T) represents a novel species in a novel genus of the family Rhodobacteraceae, for which the name Citreimonas salinaria gen. nov., sp. nov. is proposed. The type strain of Citreimonas salinaria is CL-SP20(T) (=KCCM 42116(T)=JCM 13036(T)).

Bacterial Typing Techniques↗
PubMed2006

Predominance of Roseobacter, Sulfitobacter, Glaciecola and Psychrobacter in seawater collected off Ushuaia, Argentina, Sub-Antarctica.

Bacterial diversity in sub-Antarctic seawater, collected off Ushuaia, Argentina, was examined using a culture independent approach. The composition of the 16S rRNA gene libraries from seawater and seawater contaminated with the water soluble fraction of crude oil was statistically different (P value 0.001). In both libraries, clones representing the Alphaproteobacteria, Gammaproteobacteria, the Cytophaga-Flavobacterium-Bacteroidetes group and unculturable bacteria were dominant. Clones associated with the genera Roseobacter, Sulfitobacter, Staleya, Glaciecola, Colwellia, Marinomonas, Cytophaga and Cellulophaga were common to both the libraries. However, clones associated with Psychrobacter, Arcobacter, Formosa algae, Polaribacter, Ulvibacter and Tenacibaculum were found only in seawater contaminated with hydrocarbons (Table 1). Further, the percentage of clones of Roseobacter, Sulfitobacter and Glaceicola was high in seawater (43%, 90% and 12% respectively) compared to seawater contaminated with hydrocarbons (35%, 4% and 9% respectively). One of the clones F2C63 showed 100% similarity with Marinomonas ushuaiensis a bacterium identified by us from the same site.

Alteromonadaceae↗
PubMed2006

Culture conditions of Roseobacter strain 27-4 affect its attachment and biofilm formation as quantified by real-time PCR.

The fish probiotic bacterium Roseobacter strain 27-4 grows only as rosettes and produces its antibacterial compound under static growth conditions. It forms three-dimensional biofilms when precultured under static conditions. We quantified attachment of Roseobacter strain 27-4 using a direct real-time PCR method and demonstrated that the bacteria attached more efficiently to surfaces during static growth than under aerated conditions.

Bacterial Adhesion↗
PubMed2006

Environmental biology of the marine Roseobacter lineage.

The Roseobacter lineage is a phylogenetically coherent, physiologically heterogeneous group of alpha-Proteobacteria comprising up to 25% of marine microbial communities, especially in coastal and polar oceans, and it is the only lineage in which cultivated bacteria are closely related to environmental clones. Currently 41 subclusters are described, covering all major marine ecological niches (seawater, algal blooms, microbial mats, sediments, sea ice, marine invertebrates). Members of the Roseobacter lineage play an important role for the global carbon and sulfur cycle and the climate, since they have the trait of aerobic anoxygenic photosynthesis, oxidize the greenhouse gas carbon monoxide, and produce the climate-relevant gas dimethylsulfide through the degradation of algal osmolytes. Production of bioactive metabolites and quorum-sensing-regulated control of gene expression mediate their success in complex communities. Studies of representative isolates in culture, whole-genome sequencing, e.g., of Silicibacter pomeroyi, and the analysis of marine metagenome libraries have started to reveal the environmental biology of this important marine group.

Anti-Bacterial Agents↗
PubMed1994

Structure and function of the tetraheme cytochrome associated to the reaction center of Roseobacter denitrificans.

We have characterized the tetrahemic RC bound cytochrome isolated from the quasi-photosynthetic bacterium Roseobacter denitrificans in terms of absorption spectrum, redox property and orientation with respect to the membrane plane. The heme, designated H1, which possesses the highest redox midpoint potential (+290 mV), absorbs at 555 nm. Its plane makes an angle of 40 degrees with the membrane plane. The second high potential heme, H2 (+240 mV), peaks at 554 nm and makes a tilt of 55 degrees with the membrane. The two low potential hemes, L1 and L2, present a similar and rather high redox midpoint potential (+90 mV). They absorb at 553 nm and 550 nm. One of these hemes is oriented at 40 degrees while the other makes an angle of 90 degrees with the membrane plane. The soluble cytochrome c551 completes the cyclic electron transfer between the RC and the bc1 complex. Both the oxidation and the re-reduction of cytochrome c551 are diffusible processes. Under semi-aerobic conditions, one of the low potential hemes is photo-oxidized under illumination but only extremely slowly re-reduced. This explains the requirement of high aerobic conditions for growth of Roseobacter denitrificans cells in the light.

Bacteria↗
PubMed2002

Possible quorum sensing in marine snow bacteria: production of acylated homoserine lactones by Roseobacter strains isolated from marine snow.

We report here, for the first time, that bacteria associated with marine snow produce communication signals involved in quorum sensing in gram-negative bacteria. Four of 43 marine microorganisms isolated from marine snow were found to produce acylated homoserine lactones (AHLs) in well diffusion and thin-layer chromatographic assays based on the Agrobacterium tumefaciens reporter system. Three of the AHL-producing strains were identified by 16S ribosomal DNA gene sequence analysis as Roseobacter spp., and this is the first report of AHL production by these alpha-PROTEOBACTERIA: It is likely that AHLs in Roseobacter species and other marine snow bacteria govern phenotypic traits (biofilm formation, exoenzyme production, and antibiotic production) which are required mainly when the population reaches high densities, e.g., in the marine snow community.

4-Butyrolactone↗
PubMed1997

Structure of the puf operon of the obligately aerobic, bacteriochlorophyll alpha-containing bacterium Roseobacter denitrificans OCh114 and its expression in a Rhodobacter capsulatus puf puc deletion mutant.

Roseobacter denitrificans (Erythrobacter species strain OCh114) synthesizes bacteriochlorophyll a (BChl) and the photosynthetic apparatus only in the presence of oxygen and is unable to carry out primary photosynthetic reactions and to grow photosynthetically under anoxic conditions. The puf operon of R. denitrificans has the same five genes in the same order as in many photosynthetic bacteria, i.e., pufBALMC. PufC, the tetraheme subunit of the reaction center (RC), consists of 352 amino acids (Mr, 39,043); 20 and 34% of the total amino acids are identical to those of PufC of Chloroflexus aurantiacus and Rubrivivax gelatinosus, respectively. The N-terminal hydrophobic domain is probably responsible for anchoring the subunit in the membrane. Four heme-binding domains are homologous to those of PufC in several purple bacteria. Sequences similar to pufQ and pufX of Rhodobacter capsulatus were not detected on the chromosome of R. denitrificans. The puf operon of R. denitrificans was expressed in trans in Escherichia coli, and all gene products were synthesized. The Roseobacter puf operon was also expressed in R. capsulatus CK11, a puf puc double-deletion mutant. For the first time, an RC/light-harvesting complex I core complex was heterologously synthesized. The strongest expression of the R. denitrificans puf operon was observed under the control of the R. capsulatus puf promoter, in the presence of pufQ and pufX and in the absence of pufC. Charge recombination between the primary donor P+ and the primary ubiquinone Q(A)- was observed in the transconjugant, showing that the M and L subunits of the RC were correctly assembled. The transconjugants did not grow photosynthetically under anoxic conditions.

Amino Acid Sequence↗
PubMed1999

Structural and functional analyses of photosynthetic regulatory genes regA and regB from Rhodovulum sulfidophilum, Roseobacter denitrificans, and Rhodobacter capsulatus.

Genes coding for putative RegA, RegB, and SenC homologues were identified and characterized in the purple nonsulfur photosynthetic bacteria Rhodovulum sulfidophilum and Roseobacter denitrificans, species that demonstrate weak or no oxygen repression of photosystem synthesis. This additional sequence information was then used to perform a comparative analysis with previously sequenced RegA, RegB, and SenC homologues obtained from Rhodobacter capsulatus and Rhodobacter sphaeroides. These are photosynthetic bacteria that exhibit a high level of oxygen repression of photosystem synthesis controlled by the RegA-RegB two-component regulatory system. The response regulator, RegA, exhibits a remarkable 78.7 to 84.2% overall sequence identity, with total conservation within a putative helix-turn-helix DNA-binding motif. The RegB sensor kinase homologues also exhibit a high level of sequence conservation (55.9 to 61.5%) although these additional species give significantly different responses to oxygen. A Rhodovulum sulfidophilum mutant lacking regA or regB was constructed. These mutants produced smaller amounts of photopigments under aerobic and anaerobic conditions, indicating that the RegA-RegB regulon controls photosynthetic gene expression in this bacterium as it does as in Rhodobacter species. Rhodobacter capsulatus regA- or regB-deficient mutants recovered the synthesis of a photosynthetic apparatus that still retained regulation by oxygen tension when complemented with reg genes from Rhodovulum sulfidophilum and Roseobacter denitrificans. These results suggest that differential expression of photosynthetic genes in response to aerobic and anaerobic growth conditions is not the result of altered redox sensing by the sensor kinase protein, RegB.

Aerobiosis↗
PubMed2004

Structural characterization of a binuclear center of a Cu-containing NO reductase homologue from Roseobacter denitrificans: EPR and resonance Raman studies.

Aerobic phototrophic bacterium Roseobacter denitrificans has a nitric oxide reductase (NOR) homologue with cytochrome c oxidase (CcO) activity. It is composed of two subunits that are homologous with NorC and NorB, and contains heme c, heme b, and copper in a 1:2:1 stoichiometry. This enzyme has virtually no NOR activity. Electron paramagnetic resonance (EPR) spectra of the air-oxidized enzyme showed signals of two low-spin hemes at 15 K. The high-spin heme species having relatively low signal intensity indicated that major part of heme b3 is EPR-silent due to an antiferromagnetic coupling to an adjacent CuB forming a Fe-Cu binuclear center. Resonance Raman (RR) spectrum of the oxidized enzyme suggested that heme b3 is six-coordinate high-spin species and the other hemes are six-coordinate low-spin species. The RR spectrum of the reduced enzyme showed that all the ferrous hemes are six-coordinate low-spin species. Nu(Fe-CO) and nu(C-O) stretching modes were observed at 523 and 1969 cm(-1), respectively, for CO-bound enzyme. In spite of the similarity to NOR in the primary structure, the frequency of nu(Fe-CO) mode is close to those of aa3- and bo3-type oxidases rather than that of NOR.

Copper↗
PubMed2005

Roseovarius crassostreae sp. nov., a member of the Roseobacter clade and the apparent cause of juvenile oyster disease (JOD) in cultured Eastern oysters.

An alpha-proteobacterium has been identified which is believed to be the causative agent of juvenile oyster disease (JOD). Since its first isolation in 1997, the bacterium has been recovered as the numerically dominant species from JOD-affected animals throughout the north-eastern United States (Maine, New York and Massachusetts). Colonies are usually beige to pinkish-beige, although the majority of isolates recovered in 2003 from an epizootic in Martha's Vineyard, Massachusetts, produce colonies with a greenish-yellow appearance. The cells are Gram-negative, aerobic, strictly marine and rod or ovoid in appearance. They are actively motile by one or two flagella, but cells are also observed to produce tufts of polar fimbriae. The principal fatty acid in whole cells is C(18:1)omega7c and other characteristic fatty acids are C(16:0), C(10:0) 3-OH, 11-methyl C(18:1)omega7c and C(18:0). Almost without exception, isolates have 16S rRNA gene sequences that are 100% identical to each other. Phylogenetic analyses place the organism within the Roseobacter clade of the alpha-Proteobacteria, with moderate bootstrap support for inclusion in the genus Roseovarius. DNA-DNA relatedness values from pairwise comparisons of this organism with the type species of the genus (Roseovarius tolerans) and the only other described species in this genus, Roseovarius nubinhibens, were 11 and 47%, respectively. Phenotypic and biochemical dissimilarities also support the assignment of this bacterium to a novel species. The name Roseovarius crassostreae sp. nov. is proposed, with the type strain CV919-312(T) (=ATCC BAA-1102(T)=DSM 16950(T)).

Animals↗
PubMed2006

Shimia marina gen. nov., sp. nov., a novel bacterium of the Roseobacter clade isolated from biofilm in a coastal fish farm.

A rod-shaped marine bacterium, CL-TA03(T), isolated from a biofilm in a coastal fish farm in Tongyeong, Korea, was characterized for physiological and biochemical features, fatty acid profile and phylogenetic position based on 16S rRNA gene sequences. Analysis of the 16S rRNA gene sequence revealed a clear affiliation with the family Rhodobacteraceae. Phylogenetic analysis of the 16S rRNA gene sequence showed that the closest relatives of CL-TA03(T) were Thalassobius gelatinovorus and Thalassobius mediterraneus (95.6 % similarity). The sequence similarities between CL-TA03(T) and other type species of the Roseobacter lineage ranged from 92.4 to 95.4 %. Strain CL-TA03(T) is motile and grows on marine agar as colourless or beige colonies. The strain is able to grow optimally in the range of 3-5 % sea salts. It grows within a temperature range of 15-35 degrees C and at pH 6-10. The fatty acids are dominated by 18 : 1omega7c (64.1 %) and 11-methyl 18 : 1omega7c (10.6 %). The DNA G+C content is 57.2 mol%. According to physiological data, fatty acid composition and phylogenetic analysis of the 16S rRNA gene sequence, CL-TA03(T) is considered to represent a new genus in the family Rhodobacteraceae and the name Shimia marina gen. nov., sp. nov. is proposed. The type strain of Shimia marina is CL-TA03(T) (=KCCM 42117(T)=JCM 13038(T)).

Agar↗
PubMed2004

Antibiotic production by a Roseobacter clade-affiliated species from the German Wadden Sea and its antagonistic effects on indigenous isolates.

A strain affiliated with the Roseobacter clade and producing a new antibiotic named tropodithietic acid (L. Liang, Ph.D. thesis, University of Göttingen, Göttingen, Germany, 2003) was isolated from the German Wadden Sea. The compound showed strong inhibiting properties with respect to marine bacteria of various taxa and marine algae. Antibiotic production was found to occur during the complete growth phase. Strain mutants without antagonistic properties appeared several times spontaneously.

Anti-Bacterial Agents↗
PubMed2006

Unexpected diversity of bacteria capable of carbon monoxide oxidation in a coastal marine environment, and contribution of the Roseobacter-associated clade to total CO oxidation.

The species diversity, phylogenetic affiliations, and physiological activity rates of carbon monoxide-oxidizing microorganisms were investigated, using new isolates from surface waters collected from the coast of New England and type strains from established collections. A direct isolation method allowed the simultaneous recovery of organisms with different growth rates and nutritional requirements and the identification of marine microorganisms that oxidize CO at an environmentally relevant concentration (42 nM CO). Isolates that oxidized CO at environmentally relevant rates (>4.5x10(-11) nmol CO oxidized cell-1 h-1) were taxonomically diverse, with representatives in the alpha and gamma subclasses of the Proteobacteria and the phylum Bacteroidetes, and represent a hitherto unreported metabolic function for several diverse microbial types. Isolates and type strains having the greatest specific rates of CO metabolism (1.1x10(-10) to 2.3x10(-10) nmol CO oxidized cell-1 h-1) belonged to the Roseobacter-associated clade (RAC) of the alpha subclass of the Proteobacteria. By using triple-labeled slide preparations, differential counts of active CO-oxidizing RAC cells, total RAC cells, and total bacterial cell counts in environmental samples were obtained. RAC organisms were a major component of total cell numbers (36%). Based on the density of active CO-oxidizing RAC cells in natural samples and RAC-specific metabolic activities determined for pure cultures, active CO-oxidizing RAC cells may contribute up to 15% of the total CO oxidation occurring in coastal waters.

Carbon Monoxide↗
PubMed2006

The complete genome sequence of Roseobacter denitrificans reveals a mixotrophic rather than photosynthetic metabolism.

Purple aerobic anoxygenic phototrophs (AAPs) are the only organisms known to capture light energy to enhance growth only in the presence of oxygen but do not produce oxygen. The highly adaptive AAPs compose more than 10% of the microbial community in some euphotic upper ocean waters and are potentially major contributors to the fixation of the greenhouse gas CO2. We present the complete genomic sequence and feature analysis of the AAP Roseobacter denitrificans, which reveal clues to its physiology. The genome lacks genes that code for known photosynthetic carbon fixation pathways, and most notably missing are genes for the Calvin cycle enzymes ribulose bisphosphate carboxylase (RuBisCO) and phosphoribulokinase. Phylogenetic evidence implies that this absence could be due to a gene loss from a RuBisCO-containing alpha-proteobacterial ancestor. We describe the potential importance of mixotrophic rather than autotrophic CO2 fixation pathways in these organisms and suggest that these pathways function to fix CO2 for the formation of cellular components but do not permit autotrophic growth. While some genes that code for the redox-dependent regulation of photosynthetic machinery are present, many light sensors and transcriptional regulatory motifs found in purple photosynthetic bacteria are absent.

Amino Acid Sequence↗
PubMed1993

Some properties and occurrence of cytochrome c-552 in the aerobic photosynthetic bacterium Roseobacter denitrificans.

Characteristics and occurrence of cytochrome c-552 from an aerobic photosynthetic bacterium, Roseobacter denitrificans, were described. Relative molecular mass of the cytrochrome was 13.5 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and 15,000 by gel filtration. This cytochrome was a acidic protein having a pI of 5.6 and Em was +215 mV at pH 7.0. Absorption peaks were at 278, 408 and 524 nm in the oxidized form and 416, 523 and 552 nm in the reduced form. Amino acid composition and N-terminal amino acid sequence of cytochrome c-552 determined for 24 residues had low similarities to those of cytochrome c-551 of this bacterium, which is homologous to cytochrome c2, although the physico-chemical properties of these two cytochromes were similar to each other. Cytochrome c-552 was maximally synthesized in the light under aerobic conditions but not in the dark. The synthesis also occurred in the presence of alternative acceptors such as trimethylamine N-oxide (TMAO) and nitrate under anaerobic conditions. Our results suggest that cytochrome c-552 is involved in TMAO respiration and denitrification in R. denitrificans, although the effect of light remains to be solved.

Amino Acid Sequence↗
PubMed1999

The Benefit of a Roseobacter Species on the Survival of Scallop Larvae.

: A marine strain (BS107), identified as a Roseobacter species, was antagonistic to Vibrio species on agar plates. Results suggested that the inhibitory effect was displayed only in the presence of another bacterium. Quantification of the antibacterial activity showed that 48-hour-coculture supernatants from BS107 and another bacterial strain (V. anguillarum 408) reached the highest titers of bacterial inhibition. The antibacterial substance was also liberated when supernatants from V. anguillarum 408 were added to pure cultures of the inhibition-productive bacterium. The presence of a proteinaceous molecule may induce BS107 to display the inhibitory effect. The antibacterial substance was sensitive to trypsin (8000 U/ml) and stable at 100 degrees C. Cell extracts of the isolate BS107 (10(6) cells/ml) significantly enhanced scallop larval survival, thus being beneficial to the rearing process.

Journal Article↗
PubMed2001

Respiratory electron transport and light-induced energy transduction in membranes from the aerobic photosynthetic bacterium Roseobacter denitrificans.

Membrane fragments isolated from the aerobic phototrophic bacterium Roseobacter denitrificans were examined. Ninety-five percent of the total NADH-dependent oxidative activity was inhibited either by antimycin A or myxothiazol, two specific inhibitors of the cytochrome bc1 complex, which indicates that the respiratory electron transport chain is linear. In agreement with this finding, light-induced oxygen uptake, an electron transport activity catalyzed by the "alternative quinol oxidase pathway" in membranes of several facultative phototrophic species, was barely detectable in membranes of Rsb. denitrificans. Redox titrations at 561-575 nm, 552-540 nm, and 602-630 nm indicated the presence of three b-type cytochromes (Em,7 of +244 +/- 8, +24 +/- 3, -163 +/- 11 mV), four c-type cytochromes (Em,7 of +280 +/- 10, +210 +/- 5, +125 +/- 8, and 20 +/- 3 mV) and two a-type cytochromes (Em,7 of +335 +/- 15, +218 +/- 18 mV). The latter two a-type hemes were shown to be involved in cytochrome c oxidase activity, which was inhibited by both cyanide (I50 = 2 microM) and azide (I50 = 1 mM), while a soluble cytochrome c (c551, Em,7 = +217 +/- 2 mV) was shown to be the physiological electron carrier connecting the bc1 complex to the cytochrome c oxidase. A comparison of the ATP synthesis generated by continuous light in membranes of Rsb. denitrificans and Rhodobacter capsulatus showed that in both bacterial species photophosphorylation requires a membrane redox poise at the equilibrium (Eh > or = +80 < or = +140 mV), close to the oxidation-reduction potential of the ubiquinone pool. These data, taken together, suggest that, although the photosynthetic apparatus of Rsb. denitrificans is functionally similar to that of typical anoxygenic phototrophs, e.g. Rba. capsulatus, the in vivo requirement of a suitable redox state at the ubiquinone pool level restricts the growth capacity of Rsb. denitrificans to oxic conditions.

Bacteria, Aerobic↗