SEARCH · PubMed Health

Results for “Roseobacter”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed2006

Reclassification of Roseobacter gallaeciensis Ruiz-Ponte et al. 1998 as Phaeobacter gallaeciensis gen. nov., comb. nov., description of Phaeobacter inhibens sp. nov., reclassification of Ruegeria algicola (Lafay et al. 1995) Uchino et al. 1999 as Marinovum algicola gen. nov., comb. nov., and emended descriptions of the genera Roseobacter, Ruegeria and Leisingera.

A heterotrophic, antibiotic-producing bacterium, strain T5(T), was isolated from the German Wadden Sea, located in the southern region of the North Sea. Sequence analysis of the 16S rRNA gene of this strain demonstrated close affiliation with Roseobacter gallaeciensis BS107(T) (99 % similarity), but the results of genotypic (DNA-DNA hybridization and DNA G + C content) and phenotypic characterization revealed that strain T5(T) represents a novel species. The novel organism is strictly aerobic, Gram-negative, rod-shaped, motile and forms brown-pigmented colonies. Strain T5(T) produces the antibiotic tropodithietic acid throughout the exponential phase which inhibits the growth of bacteria from different taxa, as well as marine algae. Strain T5(T) requires sodium ions and utilizes a wide range of substrates, including oligosaccharides, sugar alcohols, organic acids and amino acids. The DNA G + C content is 55.7 mol%. Comparative 16S rRNA gene sequence analysis revealed that strains T5(T) and Roseobacter gallaeciensis BS107(T) group with Leisingera methylohalidivorans as their closest described relative within the Roseobacter clade (97.9 and 97.6 % sequence similarity, respectively) and with Ruegeria algicola (96.6 and 96.5 % similarity, respectively) of the Alphaproteobacteria. Comparison of strains T5(T) and Roseobacter gallaeciensis BS107(T) with Roseobacter denitrificans and Roseobacter litoralis showed striking differences in 16S rRNA gene sequence similarities, chemical composition, pigmentation, presence of bacteriochlorophyll a and antibiotic production. On the basis of these results, it is proposed that Roseobacter gallaeciensis is reclassified as the type species of a new genus, Phaeobacter, as Phaeobacter gallaeciensis comb. nov. (type strain BS107(T) = CIP 105210(T) = ATCC 700781(T) = NBRC 16654(T) = DSM 17395(T)). Strain T5(T) (=LMG 22475(T) = DSM 16374(T)) is proposed as the type strain of a novel species of this genus, Phaeobacter inhibens sp. nov. At the same time, emended descriptions are provided of the genera Roseobacter, Ruegeria and Leisingera, as well as reclassifying Ruegeria algicola as the type species of a new genus, Marinovum, with the name Marinovum algicola comb. nov.

Chromosomes, Bacterial↗

PubMed2006

Production of antibacterial compounds and biofilm formation by Roseobacter species are influenced by culture conditions.

Bacterial communities associated with marine algae are often dominated by members of the Roseobacter clade, and in the present study, we describe Roseobacter phenotypes that may provide this group of bacteria with selective advantages when colonizing this niche. Nine of 14 members of the Roseobacter clade, of which half were isolated from cultures of the dinoflagellate Pfiesteria piscicida, produced antibacterial compounds. Many non-Roseobacter marine bacteria were inhibited by sterile filtered supernatants of Silicibacter sp. TM1040 and Phaeobacter (formerly Roseobacter) strain 27-4, which had the highest production of antibacterial compound. In contrast, Roseobacter strains were susceptible only when exposed to concentrated compound. The production of antibacterial compound was influenced by the growth conditions, as production was most pronounced when bacteria were grown in liquid medium under static conditions. Under these conditions, Silicibacter sp. TM1040 cells attached to one another, forming rosettes, as has previously been reported for Phaeobacter 27-4. A spontaneous Phaeobacter 27-4 mutant unable to form rosettes was also defective in biofilm formation and the production of antibacterial compound, indicating a possible link between these phenotypes. Rosette formation was observed in 8 of 14 Roseobacter clade strains examined and was very pronounced under static growth in 5 of these strains. Attachment to surfaces and biofilm formation at the air-liquid interface by these five strains was greatly facilitated by growth conditions that favored rosette formation, and rosette-forming strains were 13 to 30 times more efficient in attaching to glass compared to strains under conditions where rosette formation was not pronounced. We hypothesize that the ability to produce antibacterial compounds that principally inhibit non-Roseobacter species, combined with an enhancement in biofilm formation, may give members of the Roseobacter clade a selective advantage and help to explain the dominance of members of this clade in association with marine algal microbiota.

Animals↗

PubMed2000

Key aromatic-ring-cleaving enzyme, protocatechuate 3,4-dioxygenase, in the ecologically important marine Roseobacter lineage.

Aromatic compound degradation in six bacteria representing an ecologically important marine taxon of the alpha-proteobacteria was investigated. Initial screens suggested that isolates in the Roseobacter lineage can degrade aromatic compounds via the beta-ketoadipate pathway, a catabolic route that has been well characterized in soil microbes. Six Roseobacter isolates were screened for the presence of protocatechuate 3,4-dioxygenase, a key enzyme in the beta-ketoadipate pathway. All six isolates were capable of growth on at least three of the eight aromatic monomers presented (anthranilate, benzoate, p-hydroxybenzoate, salicylate, vanillate, ferulate, protocatechuate, and coumarate). Four of the Roseobacter group isolates had inducible protocatechuate 3, 4-dioxygenase activity in cell extracts when grown on p-hydroxybenzoate. The pcaGH genes encoding this ring cleavage enzyme were cloned and sequenced from two isolates, Sagittula stellata E-37 and isolate Y3F, and in both cases the genes could be expressed in Escherichia coli to yield dioxygenase activity. Additional genes involved in the protocatechuate branch of the beta-ketoadipate pathway (pcaC, pcaQ, and pobA) were found to cluster with pcaGH in these two isolates. Pairwise sequence analysis of the pca genes revealed greater similarity between the two Roseobacter group isolates than between genes from either Roseobacter strain and soil bacteria. A degenerate PCR primer set targeting a conserved region within PcaH successfully amplified a fragment of pcaH from two additional Roseobacter group isolates, and Southern hybridization indicated the presence of pcaH in the remaining two isolates. This evidence of protocatechuate 3, 4-dioxygenase and the beta-ketoadipate pathway was found in all six Roseobacter isolates, suggesting widespread abilities to degrade aromatic compounds in this marine lineage.

Adipates↗

PubMed2000

Differentiation of newly described antarctic bacterial isolates related to Roseobacter species based on 16S-23S rDNA internal transcribed spacer sequences.

The 16S-23S rDNA internal transcribed spacer (ITS) of Roseobacter denitrificans, Roseobacter litoralis, Ruegeria algicola and strains of the recently described species Antarctobacter heliothermus and Roseovarius tolerans were analysed in order to examine DNA sequence variations and to draw conclusions about inter- and intraspecific relationships. A. heliothermus included four strains with an ITS fragment length of 1092 bp. Roseovarius tolerans was described on the basis of eight strains. Five of these harboured two ITS fragments of different lengths (959 and about 1100 bp), while the others had one fragment of either 1083 bp (two strains) or 1165 bp (one strain). ITS lengths of the related species Roseobacter denitrificans, Roseobacter litoralis and Ruegeria algicola were found to be 980, 984 and 1158 bp, respectively. Phylogenetic analyses of the DNA sequences allowed species affiliation of strains with sequence length differences of > 200 bp and recognition of relationships based on a well-supported ITS tree. The strains of A. heliothermus and Roseovarius tolerans each formed a monophyletic branch and they were separated from each other by Ruegeria algicola. This species was now clearly separated from Roseobacter denitrificans and Roseobacter litoralis, which corresponded to the new genus affiliation of Ruegeria algicola. These data were additionally supported by analyses of the structure, relative position and order of genes for tRNA(Ile) and tRNA(Ala) found within the ITS of each strain. Comparative DNA sequence analyses of ITS and 16S rDNA revealed limitations, on species and strain levels, with respect to the phylogenetic resolution of the 16S rDNA due to the limited number of informative (variable) sites, while ITS sequence analyses provided more variable and sufficiently conserved positions to discriminate between strains and to reconstruct their taxonomic relationships.

Alphaproteobacteria↗

PubMed2003

Aerobic anoxygenic photosynthesis in Roseobacter clade bacteria from diverse marine habitats.

The marine Roseobacter clade comprises several genera of marine bacteria related to the uncultured SAR83 cluster, the second most abundant marine picoplankton lineage. Cultivated representatives of this clade are physiologically heterogeneous, and only some have the capability for aerobic anoxygenic photosynthesis, a process of potentially great ecological importance in the world's oceans. In an attempt to correlate phylogeny with ecology, we investigated the diversity of Roseobacter clade strains from various marine habitats (water samples, biofilms, laminariae, diatoms, and dinoflagellate cultures) by using the 16S rRNA gene as a phylogenetic marker gene. The potential for aerobic anoxygenic photosynthesis was determined on the genetic level by PCR amplification and sequencing of the pufLM genes of the bacterial photosynthesis reaction center and on the physiological level by detection of bacteriochlorophyll (Bchl) a. A collection of ca. 1,000 marine isolates was screened for members of the marine Roseobacter clade by 16S rRNA gene-directed multiplex PCR and sequencing. The 42 Roseobacter clade isolates found tended to form habitat-specific subclusters. The pufLM genes were detected in two groups of strains from dinoflagellate cultures but in none of the other Roseobacter clade isolates. Strains within the first group (the DFL-12 cluster) also synthesized Bchl a. Strains within the second group (the DFL-35 cluster) formed a new species of Roseovarius and did not produce Bchl a under the conditions investigated here, thus demonstrating the importance of genetic methods for screening of cultivation-dependent metabolic traits. The pufL genes of the dinoflagellate isolates were phylogenetically closely related to pufL genes from Betaproteobacteria, confirming similar previous observations which have been interpreted as indications of gene transfer events.

Aerobiosis↗

PubMed2004

Seasonal incidence of autochthonous antagonistic Roseobacter spp. and Vibrionaceae strains in a turbot larva (Scophthalmus maximus) rearing system.

Bacteria inhibitory to fish larval pathogenic bacteria were isolated from two turbot larva rearing farms over a 1-year period. Samples were taken from the rearing site, e.g., tank walls, water, and feed for larvae, and bacteria with antagonistic activity against Vibrio anguillarum were isolated using a replica plating assay. Approximately 19,000 colonies were replica plated from marine agar plates, and 341 strains were isolated from colonies causing clearing zones in a layer of V. anguillarum. When tested in a well diffusion agar assay, 173 strains retained the antibacterial activity against V. anguillarum and Vibrio splendidus. Biochemical tests identified 132 strains as Roseobacter spp. and 31 as Vibrionaceae strains. Partial sequencing of the 16S rRNA gene of three strains confirmed the identification as Roseobacter gallaeciensis. Roseobacter spp. were especially isolated in the spring and early summer months. Subtyping of the 132 Roseobacter spp. strains by randomly amplified polymorphic DNA with two primers revealed that the strains formed a very homogeneous group. Hence, it appears that the same subtype was present at both fish farms and persisted during the 1-year survey. This indicates either a common, regular source of the subtype or the possibility that a particular subtype has established itself in some areas of the fish farm. Thirty-one antagonists were identified as Vibrio spp., and 18 of these were V. anguillarum but not serotype O1 or O2. Roseobacter spp. strains were, in particular, isolated from the larval tank walls, and it may be possible to establish an antagonistic, beneficial microflora in the rearing environment of turbot larvae and thereby limit survival of pathogenic bacteria.

Animals↗

PubMed2004

Dimethylsulfoniopropionate metabolism by Pfiesteria-associated Roseobacter spp.

The Roseobacter clade of marine bacteria is often found associated with dinoflagellates, one of the major producers of dimethylsulfoniopropionate (DMSP). In this study, we tested the hypothesis that Roseobacter species have developed a physiological relationship with DMSP-producing dinoflagellates mediated by the metabolism of DMSP. DMSP was measured in Pfiesteria and Pfiesteria-like (Cryptoperidiniopsis) dinoflagellates, and the identities and metabolic potentials of the associated Roseobacter species to degrade DMSP were determined. Both Pfiesteria piscicida and Pfiesteria shumwayae produce DMSP with an average intracellular concentration of 3.8 microM. Cultures of P. piscicida or Cryptoperidiniopsis sp. that included both the dinoflagellates and their associated bacteria rapidly catabolized 200 microM DMSP (within 30 h), and the rate of catabolism was much higher for P. piscicida cultures than for P. shumwayae cultures. The community of bacteria from P. piscicida and Cryptoperidiniopsis cultures degraded DMSP with the production of dimethylsulfide (DMS) and acrylate, followed by 3-methylmercaptopropionate (MMPA) and methanethiol (MeSH). Four DMSP-degrading bacteria were isolated from the P. piscicida cultures and found to be taxonomically related to Roseobacter species. All four isolates produced MMPA from DMSP. Two of the strains also produced MeSH and DMS, indicating that they are capable of utilizing both the lyase and demethylation pathways. The diverse metabolism of DMSP by the dinoflagellate-associated Roseobacter spp. offers evidence consistent with a hypothesis that these bacteria benefit from association with DMSP-producing dinoflagellates.

Animals↗

PubMed2005

Ecology, inhibitory activity, and morphogenesis of a marine antagonistic bacterium belonging to the Roseobacter clade.

Roseobacter strain 27-4 has been isolated from a turbot larval rearing unit and is capable of reducing mortality in turbot egg yolk sac larvae. Here, we demonstrate that the supernatant of Roseobacter 27-4 is lethal to the larval pathogens Vibrio anguillarum and Vibrio splendidus in a buffer system and inhibited their growth in marine broth. Liquid chromatography (LC) with both UV spectral detection and high-resolution mass spectrometry (HR-MS) identified the known antibacterial compound thiotropocin or its closely related precursor tropodithietic acid in the bioactive fractions. Antibacterial activity correlated with the appearance of a brownish pigment and was only formed in marine broth under static growth conditions. A thick biofilm of multicellular star-shaped aggregated cells formed at the air-liquid interface under static growth conditions. Here, the bioactive compound was the base peak in the LC-UV chromatograms of the extracts where it constituted 15% of the total peak area. Aerated conditions results in 10-fold-higher cell yield, however, cultures were nonpigmented, did not produce antibacterial activity, and grew as single cells. Production of antibacterial compounds may be quorum regulated, and we identified the acylated homoserine lactone (3-hydroxy-decanoyl homoserine lactone) from cultures of Roseobacter 27-4 using LC-HR-MS. The signal molecule was primarily detected in stagnant cultures. Roseobacter 27-4 grew between 10 and 30 degrees C but died rapidly at 37 degrees C. Also, the antibacterial compounds was sensitive to heat and was inactivated at 37 degrees C in less than 2 days and at 25 degrees C in 8 days. Using Roseobacter 27-4 as a probiotic culture will require that is be established in stagnant or adhered conditions and, due to the temperature sensitivity of the active compound, constant production must be ensured.

Animals↗

PubMed2006

Coupled photochemical and enzymatic Mn(II) oxidation pathways of a planktonic Roseobacter-Like bacterium.

Bacteria belonging to the Roseobacter clade of the alpha-Proteobacteria occupy a wide range of environmental niches and are numerically abundant in coastal waters. Here we reveal that Roseobacter-like bacteria may play a previously unrecognized role in the oxidation and cycling of manganese (Mn) in coastal waters. A diverse array of Mn(II)-oxidizing Roseobacter-like species were isolated from Elkhorn Slough, a coastal estuary adjacent to Monterey Bay in California. One isolate (designated AzwK-3b), in particular, rapidly oxidizes Mn(II) to insoluble Mn(III, IV) oxides. Interestingly, AzwK-3b is 100% identical (at the 16S rRNA gene level) to a previously described Pfiesteria-associated Roseobacter-like bacterium, which is not able to oxidize Mn(II). The rates of manganese(II) oxidation by live cultures and cell-free filtrates are substantially higher when the preparations are incubated in the presence of light. The rates of oxidation by washed cell extracts, however, are light independent. Thus, AzwK-3b invokes two Mn(II) oxidation mechanisms when it is incubated in the presence of light, in contrast to the predominantly direct enzymatic oxidation in the dark. In the presence of light, production of photochemically active metabolites is coupled with initial direct enzymatic Mn(II) oxidation, resulting in higher Mn(II) oxidation rates. Thus, Roseobacter-like bacteria may not only play a previously unrecognized role in Mn(II) oxidation and cycling in coastal surface waters but also induce a novel photooxidation pathway that provides an alternative means of Mn(II) oxidation in the photic zone.

Animals↗

PubMed2006

Isolation and characterization of novel marine Roseobacter clade members producing unique intracellular chromium-rich aggregates.

The marine Roseobacter clade comprises one of the largest fractions of heterotrophic marine bacteria and accounts for about 16% of 16S rRNA gene clones retrieved from marine bacterioplankton. Their global distribution seems to be related to oceanic water masses and their environmental and biogeochemical properties. In this study, we report isolation and characterization of novel Roseobacter clade members from the Yellow Sea, China. Phylogenetic analysis of 16S rRNA gene sequences reveals that the new isolates (YSCB1, YSCB2, YSCB3 and YSCB4) are closely related to uncultured Arctic seawater bacterium R7967 (99.57-100% sequence identity) and to the cultured Roseobacter sp. DSS-1 (99.27-99.76% sequence identity) isolated from the southeastern coastal water of the USA. Interestingly, YSCB strains possess unique intracellular chromium-containing aggregates. Therefore, these novel Roseobacter clade members exhibit a peculiar property in mineral biogeneration.

Chromium↗

PubMed1995

Roseobacter algicola sp. nov., a new marine bacterium isolated from the phycosphere of the toxin-producing dinoflagellate Prorocentrum lima.

We describe a new species on the basis of phenotypic characteristics and the results of an analysis of small-subunit rRNA sequences. Three strains of this organism were isolated from a culture of the toxin-producing dinoflagellate Prorocentrum lima. These bacteria are gram-negative, strictly aerobic, ovoid organisms that are motile by means of one or two subpolar flagella. They grow at temperatures ranging from 10 to 37 degrees C and in the presence of NaCl concentrations ranging from 0.1 to 2 M and have an absolute requirement for sodium ions. They are strictly aerobic with a nonfermentative type of metabolism and are not able to grow anaerobically in presence or absence of nitrate. They do not denitrify. They exhibit oxidase, catalase, gelatinase, esculinase, beta-galactosidase, and (to a lesser extent) amylase activities. The three strains which we examined require thiamine and biotin for growth. They grow only when glucose, trehalose, saccharose, fructose, maltose, pyruvate, malate, citrate, esculin, 2-ketoglutarate, 5-ketogluconate, glutamate, or shikimate is present as a sole carbon source. The three strains have identical small-subunit rRNA sequences. A phylogenetic analysis of these sequences revealed that these bacteria belong to the alpha subdivision of the Proteobacteria and that they form a distinct and robust monophyletic group with Roseobacter denitrificans and Roseobacter litoralis. This result and the general phenotypic characteristics of the organisms place them in the genus Roseobacter, although they do not produce bacteriochlorophyll a, in contrast to previously described Roseobacter species.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2006

Roseobacter and SAR11 dominate microbial glucose uptake in coastal North Sea waters.

Bacterial assemblages in coastal pelagic environments are exposed to pronounced temporal and spatial fluctuations in the availability of monomeric substrates. Little is known about the response of particular bacterial groups to such variability. We studied glucose incorporation at various concentrations (0.1-100 nM) by bacteria related to Roseobacter, SAR11, Gammaproteobacteria and Cytophaga-Flavobacteria in coastal North Sea waters in late winter and during a spring phytoplankton bloom dominated by Phaeocystis sp. (March and May 2004 respectively). Both the fraction of glucose-assimilating bacterial cells and the rate of substrate incorporation per active cell were higher in May. The respective contributions of the studied groups to all glucose-assimilating Bacteria were related to substrate concentration. The majority of glucose-incorporating bacterial cells at the lower concentrations were members of the Roseobacter and SAR11 clades. At both time-points the two groups formed approximately equal fractions of all glucose-incorporating bacteria. This was due to a small population of highly active Roseobacter cells and high abundances of SAR11 bacteria with low proportions of glucose-incorporating cells. By contrast, the proportion of active cells from the Cytophaga-Flavobacteria lineage substantially increased at higher levels of available substrate. The determination of concentration-dependent substrate incorporation patterns may help to better understand the different ecophysiological niches of bacterioplankton populations.

Alphaproteobacteria↗

PubMed2004

Diverse organization of genes of the beta-ketoadipate pathway in members of the marine Roseobacter lineage.

Members of the Roseobacter lineage, an ecologically important marine clade within the class alpha-Proteobacteria, harbor genes for the protocatechuate branch of the beta-ketoadipate pathway, a major catabolic route for lignin-related aromatic compounds. The genes of this pathway are typically clustered, although gene order varies among organisms. Here we characterize genes linked to pcaH and -G, which encode protocatechuate 3,4-dioxygenase, in eight closely related members of the Roseobacter lineage (pairwise 16S rRNA gene sequence identities, 92 to 99%). Sequence analysis of genomic fragments revealed five unique pca gene arrangements. Identical gene organization was found for isolates demonstrating species-level identity (i.e., >99% 16S rRNA gene similarity). In one isolate, six functionally related genes were clustered: pcaQ, pobA, pcaD, pcaC, pcaH, and pcaG. The remaining seven isolates lacked at least one of these genes in their clusters, although the relative order of the remaining genes was preserved. Three genes (pcaC, -H, and -G) were physically linked in all isolates. A highly conserved open reading frame (ORF) was found immediately downstream of pcaG in all eight isolates. Reverse transcription-PCR analysis of RNA from one isolate, Silicibacter pomeroyi DSS-3, provides evidence that this ORF is coexpressed with upstream pca genes. The absence of this ORF in similar bacterial pca gene clusters from diverse microbes suggests a niche-specific role for its protein product in Roseobacter group members. Collectively, these comparisons of bacterial pca gene organization illuminate a complex evolutionary history and underscore the widespread ecological importance of the encoded beta-ketoadipate pathway.

Adipates↗

PubMed2005

Roseobacter-like bacteria in red and mediterranean sea aerobic anoxygenic photosynthetic populations.

Bacteriochlorophyll a-containing aerobic anoxygenic phototrophs (AAnP) have been proposed to account for up to 11% of the total surface water microbial community and to potentially have great ecological importance in the world's oceans. Recently, environmental and genomic data based on analysis of the pufM gene identified the existence of alpha-proteobacteria as well as possible gamma-like proteobacteria among AAnP in the Pacific Ocean. Here we report on analyses of environmental samples from the Red and Mediterranean Seas by using pufM as well as the bchX and bchL genes as molecular markers. The majority of photosynthesis genes retrieved from these seas were related to Roseobacter-like AAnP sequences. Furthermore, the sequence of a novel photosynthetic operon organization from an uncultured Roseobacter-like bacterial artificial chromosome retrieved from the Red Sea is described. The data show the presence of Roseobacter-like bacteria in Red and Mediterranean Sea AAnP populations in the seasons analyzed.

Aerobiosis↗

PubMed1998

Roseobacter gallaeciensis sp. nov., a new marine bacterium isolated from rearings and collectors of the scallop Pecten maximus.

Four bacterial strains were isolated from larval cultures and collectors of the scallop Pecten maximus. They showed a high level of intragroup genomic relatedness (84-95%) as determined by DNA-DNA hybridization. The cells were Gram-negative, strictly aerobic, motile, ovoid rods. They grew at temperatures from 15 to 37 degrees C and from pH 7.0 to 10, but did not grow in the absence of NaCl and required growth factors. They had the ability to use a wide variety of compounds as sole carbon source: D-mannose, D-galactose, D-fructose, D-glucose, D-xylose, melibiose, trehalose, maltose, cellobiose, sucrose, mesoerythritol, D-mannitol, glycerol, D-sorbitol, meso-inositol, succinate, propionate, butyrate, gamma-aminobutyrate, DL-hydroxybutyrate, 2-ketoglutarate, pyruvate, fumarate, glycine, L-alpha-alanine, beta-alanine, L-glutamate, L-arginine, L-lysine, L-ornithine and L-proline. They exhibited oxidase and catalase activities but no denitrification activity. The isolates did not contain bacteriochlorophyll a. The G + C content ranged from 57.6 to 58 mol%. Phylogenetic analyses of the 16S rRNA sequence revealed that these isolates belong to the genus Roseobacter. On the basis of quantitative hybridization data, it is proposed that these isolates should be placed in a new species, Roseobacter gallaeciensis. The type strain is Roseobacter gallaeciensis BS107T (= CIP 105210T).

Animals↗

PubMed1995

Lipopolysaccharide and porin of Roseobacter denitrificans, confirming its phylogenetic relationship to the alpha-3 subgroup of Proteobacteria.

Roseobacter denitrificans has rough (R)-type lipopolysaccharide, containing 2-keto-3-deoxyoctonate but no hepatoses. Its lipid A has a glucosamine-containing, phosphorylated backbone. It contains the rare 3-oxotetradecanoic (3-oxomyristic) acid as the only amide-bound fatty acid and ester-bound 3-hydroxydecanoic acid, this pattern being characteristic for the alpha-3 subgroup of Proteobacteria. Treatment of the major outer-membrane protein (porin, apparent molecular mass 88 kDa) of Roseobacter denitrificans with EDTA (2 mM, 30 degrees C, 20 min) resulted in the dissociation of the oligomers into monomers (apparent molecular mass 35 kDa). EDTA-sensitive dissociation has so far been observed only within the alpha-3 subgroup of Proteobacteria. The 12 N-terminal amino acids of the monomers exhibit sequence homology with the porins of Rhodobacter capsulatus, Rhodobacter sphaeroides and Rhodopseudomonas blastica. Renaming of Roseobacter denitrificans as Rhodobacter denitrificans is suggested.

Amino Acid Sequence↗

PubMed2004

A newly discovered Roseobacter cluster in temperate and polar oceans.

Bacterioplankton phylotypes of alpha-Proteobacteria have been detected in various marine regions, but systematic biogeographical studies of their global distribution are missing. Alpha-Proteobacteria comprise one of the largest fractions of heterotrophic marine bacteria and include two clades, SAR11 and Roseobacter, which account for 26 and 16% of 16S ribosomal RNA gene clones retrieved from marine bacterioplankton. The SAR11 clade attracted much interest because related 16S rRNA gene clones were among the first groups of marine bacteria to be identified by cultivation-independent approaches and appear to dominate subtropical surface bacterioplankton communities. Here we report on the global distribution of a newly discovered cluster affiliated to the Roseobacter clade, comprising only as-yet-uncultured phylotypes. Bacteria of this cluster occur from temperate to polar regions with highest abundance in the Southern Ocean, but not in tropical and subtropical regions. Between the south Atlantic subtropical front and Antarctica, we detected two distinct phylotypes, one north and one south of the polar front, indicating that two adjacent but different oceanic provinces allow the persistence of distinct but closely related phylotypes. These results suggest that the global distribution of major marine bacterioplankton components is related to oceanic water masses and controlled by their environmental and biogeochemical properties.

Climate↗

PubMed2005

Roseovarius mucosus sp. nov., a member of the Roseobacter clade with trace amounts of bacteriochlorophyll a.

Among a group of marine isolates that were found to be positive for genes of the bacterial photosynthetic reaction centre, a strain was selected for characterization that was phylogenetically close to the genus Roseovarius. The strain, designated DFL-24T, originated from a culture of Alexandrium ostenfeldii (dinoflagellate) and contained small amounts of bacteriochlorophyll a, corresponding to about 1 % of the amount found in intensely pigmented aerobic phototrophs such as Roseobacter litoralis. Cells were rods of 0.5-0.7x1.3-3.0 microm often with uneven ends, suggesting a budding mode of division. True motility was not observed. Electron micrographs of ultrathin sections revealed a Gram-negative cell-wall structure. Cultures did not grow without addition of sea salts and tolerated up to 10 % (w/v) sea-water salts. Acetate, butyrate, tricarboxylic acid cycle intermediates, glutamate and glycerol were used as growth substrates, but not glucose or fructose. Biotin, thiamine and nicotinic acid were required as growth factors. The DNA G+C content was 63 mol%. 16S rRNA gene sequence analysis placed the strain within the Roseobacter lineage of the 'Alphaproteobacteria'. Its closest phylogenetic neighbour was Roseovarius tolerans showing 96.4 % 16S rRNA gene sequence similarity. Based also on its physiological and biochemical characteristics, the strain is considered to represent a novel species of the genus Roseovarius, Roseovarius mucosus sp. nov. Strain DFL-24T (=DSM 17069T=NCIMB 14077T) is the type strain. The 16S rRNA gene sequence of DFL-24T was found to have a similarity of 99.7 % with an unidentified strain, 253-13 (=DSM 17070), which was likewise characterized and shown to constitute another strain of the species.

Bacteriochlorophyll A↗