[Show abstract][Hide abstract] ABSTRACT: The marine metabolite tropodithietic acid (TDA), produced by several Roseobacter clade
bacteria, is known for its broad antimicrobial activity. TDA is of interest not only as a probiotic
in aquaculture, but also because it might be of use as an antibacterial agent in non-marine or
non-aquatic environments, and thus the potentially cytotoxic influences on eukaryotic cells need to
be evaluated. The present study was undertaken to investigate its effects on cells of the mammalian
nervous system, i.e., neuronal N2a cells and OLN-93 cells as model systems for nerve cells and
glia. The data show that in both cell lines TDA exerted morphological changes and cytotoxic effects
at a concentration of 0.3–0.5 �g/mL (1.4–2.4 �M). Furthermore, TDA caused a breakdown of the
mitochondrial membrane potential, the activation of extracellular signal-regulated kinases ERK1/2,
and the induction of the small heat shock protein HSP32/HO-1, which is considered as a sensor of
oxidative stress. The cytotoxic effects were accompanied by an increase in intracellular Ca2+-levels,
the disturbance of the microtubule network, and the reorganization of the microfilament system.
Hence, mammalian cells are a sensitive target for the action of TDA and react by the activation of a
stress response resulting in cell death.
[Show abstract][Hide abstract] ABSTRACT: The Roseobacter group is one of the predominant lineages in the marine environment. While most investigations focus on pelagic roseobacters, the distribution and metabolic potential of benthic representatives is less understood. In this study, the diversity of the Roseobacter group was characterized in sediment and water samples along the German/Scandinavian North Sea coast by 16S rRNA gene analysis and cultivation-based methods. Molecular analysis indicated an increasing diversity between communities of the Roseobacter group from the sea surface to the seafloor and revealed distinct compositions of free-living and attached fractions. Culture media containing dimethyl sulfide (DMS), dimethyl sulfonium propionate (DMSP) or dimethyl sulfoxide (DMSO) stimulated growth of roseobacters showing highest most probable numbers (MPN) in DMSO-containing dilutions of surface sediments (2.1×10(7) roseobacters cm(-3)). Twenty roseobacters (12 from sediments) were isolated from DMSP- and DMS-containing cultures. Sequences of the isolates represented 0.04% of all Bacteria and 4.7% of all roseobacters in the pyrosequencing dataset from sediments. Growth experiments with the isolate Shimia sp. SK013 indicated that benthic roseobacters are able to switch between aerobic and anaerobic utilization of organic sulfur compounds. This response to changing redox conditions might be an adaptation to specific environmental conditions on particles and in sediments.
[Show abstract][Hide abstract] ABSTRACT: The Gram-negative alphaproteobacterium
SB1 (DSM 26878) belongs to the marine
clade. The genome of this strain is the smallest closed genome of the
SB1 is the first described nonpolar mesophilic isolate of the genus
and the type strain of the species.
[Show abstract][Hide abstract] ABSTRACT: Dissolved organic matter (DOM) in the oceans constitutes a major carbon pool involved in global biogeochemical cycles. More than 96% of the marine DOM resists microbial degradation for thousands of years. The composition of this refractory DOM (RDOM) exhibits a molecular signature ubiquitously detected in the deep oceans. Surprisingly efficient microbial transformation of labile into stable forms of DOM has been shown previously, implying that microorganisms apparently produce far more RDOM than needed to sustain the global pool. Here we show, by assessing the microbial formation and transformation of DOM in unprecedented molecular detail for 3 years, that most of the microbial DOM is different from RDOM in the ocean. Only <0.4% of the net community production is channelled into a form of DOM that is undistinguishable from oceanic RDOM. Our study provides a molecular background for global models on the production, turnover and accumulation of marine DOM.
[Show abstract][Hide abstract] ABSTRACT: The marine bacterium Alteromonas macleodii is a copiotrophic r-strategist, but little is known about its potential to degrade polysaccharides. Here, we studied the degradation of alginate and other algal polysaccharides by A. macleodii strain 83-1 in comparison to other A. macleodii strains. Cell densities of strain 83-1 with alginate as sole carbon source were comparable to those with glucose, but the exponential phase was delayed. The genome of 83-1 was found to harbor an alginolytic system comprising five alginate lyases, whose expression was induced by alginate. The alginolytic system contains additional CAZymes, including two TonB-dependent receptors, and is part of a 24 kb genomic island unique to the A. macleodii "surface clade" ecotype. In contrast, strains of the "deep clade" ecotype contain only a single alginate lyase in a separate 7 kb island. This difference was reflected in a eightfold greater efficiency of surface clade strains to grow on alginate. Strain 83-1 furthermore hydrolyzed laminarin, pullulan, and xylan, and corresponding polysaccharide utilization loci were detected in the genome. A. macleodii alginate lyases were predominantly detected in Atlantic Ocean metagenomes. The demonstrated hydrolytic capacities are likely of ecological relevance and represent another level of adaptation among A. macleodii ecotypes.
This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Marine planktonic bacteria often live in habitats with extremely low concentrations of dissolved organic matter (DOM). To study the use of trace amounts of DOM by the facultatively oligotrophic Pseudovibrio sp. FO-BEG1, we investigated the composition of artificial and natural seawater before and after growth. We determined the concentrations of dissolved organic carbon (DOC), total dissolved nitrogen (TDN), free and hydrolysable amino acids, and the molecular composition of DOM by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR-MS). The DOC concentration of the artificial seawater we used for cultivation was 4.4 μmol C L<sup>-1</sup>, which was eight times lower compared to the natural oligotrophic seawater we used for parallel experiments (36 μmol C L <sup>-1</sup>). During the three-week duration of the experiment, cell numbers increased from 40 cells mL<sup>-1</sup> to 2x10<sup>4</sup> cells mL <sup>-1</sup> in artificial and to 3x10<sup>5</sup> cells mL <sup>-1</sup> in natural seawater. No nitrogen fixation and minor CO<sub>2</sub> fixation (< 1% of cellular carbon) was observed. Our data show that in both media, amino acids were not the main substrate for growth. Instead, FT-ICR-MS analysis revealed usage of a variety of different dissolved organic molecules, belonging to a wide range of chemical compound groups, also containing nitrogen. The present study shows that marine heterotrophic bacteria are able to proliferate with even lower DOC concentrations than available in natural ultra-oligotrophic seawater, using unexpected organic compounds to fuel their energy, carbon and nitrogen requirements.
PLoS ONE 03/2015; 10(3-3):e0121675. DOI:10.1371/journal.pone.0121675 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A heterotrophic, Gram negative, aerobic bacterium, designated strain SB1T, was isolated from surface water of the southern North Sea. Comparison of 16S rRNA gene sequences revealed that strain SB1T is affiliated to the genus Octadecabacter within the marine Roseobacter clade (family Rhodobacteraceae) with Octadecabacter antarcticus as the closest described species (98.2% sequence similarity). DNA-DNA hybridization indicated that SB1T is a distinct species within this genus. On marine agar, strain SB1T forms beige, circular and convex colonies. Cells are irregular, motile rods. Growth occurs between 4 and 25°C and is optimal at 20°C. pH ranges from 7-9 (optimum 7.5-8.5), NaCl concentrations between 1 and 6% are tolerated (optimum 2-4%). The DNA G+C base content of SB1T is 54.7 mol%. The fatty acids (>1%) comprise 10:0 3-OH, 12:1 3-OH, 16:1ω7c, 16:0, 18:2ω7, 12, 18:1ω7c, 18:0, and 11-methyl 18:1ω7c. The sole respiratory lipoquinone is ubiquinone Q-10 and the polar lipid pattern indicates the presence of the phospholipids phosphatidylglycerol and phosphatidylcholine, as well as the unidentified aminolipid AL1, phospholipids PL1 and PL3 and the lipids L1, L2 and L4. On the basis of phylogenetic and phenotypic differences strain SB1T represents a novel species in the genus Octadecabacter, for which we propose the name Octadecabacter temperatus sp. nov. The type strain is SB1T (= DSM 26878T = LMG 27946T). Furthermore, our results suggest reclassification of Octadecabacter jejudonensis as type species of a new genus, Pseudooctadecabacter, as Pseudooctadecabacter jejudonensis comb. nov. (type strain SSK2-1T = KCTC 32535T = CECT 8397T).
International Journal of Systematic and Evolutionary Microbiology 03/2015; 65(6). DOI:10.1099/ijs.0.000205 · 2.51 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The bacterial degradation of polysaccharides is central to marine carbon cycling, but little is known about the bacterial taxa that degrade specific marine polysaccharides. Here, bacterial growth and community dynamics were studied during the degradation of the polysaccharides chitin, alginate and agarose in microcosm experiments at four contrasting locations in the Southern and Atlantic Oceans. At the Southern polar front, chitin-supplemented microcosms were characterized by higher fractions of actively growing cells and a community shift from Alphaproteobacteria to Gammaproteobacteria and Bacteroidetes. At the Antarctic ice shelf, chitin degradation was associated with growth of Bacteroidetes, with 24% higher cell numbers compared with the control. At the Patagonian continental shelf, alginate and agarose degradation covaried with growth of different Alteromonadaceae populations, each with specific temporal growth patterns. At the Mauritanian upwelling, only the alginate hydrolysis product guluronate was consumed, coincident with increasing abundances of Alteromonadaceae and possibly cross-feeding SAR11. 16S rRNA gene amplicon libraries indicated that growth of the Bacteroidetes-affiliated genus Reichenbachiella was stimulated by chitin at all cold and temperate water stations, suggesting comparable ecological roles over wide geographical scales. Overall, the predominance of location-specific patterns showed that bacterial communities from contrasting oceanic biomes have members with different potentials to hydrolyse polysaccharides.
[Show abstract][Hide abstract] ABSTRACT: Diatom-dominated phytoplankton blooms in neritic seas are typically terminated by aggregation. Despite extensive studies, it is still unknown how temperature controls aggregation. Therefore, we studied aggregation in a 750 liter mesocosm experiment under simulated in situ conditions during a spring diatom bloom in the southern North Sea at Helgoland Roads. In the early phase, at the peak, and in the late phase, aggregation was examined in rolling tanks at the ambient temperature (6uC) and at 11uC. In a second set of rolling tanks, cells of Thalassiosira rotula were added to examine how this readily aggregating diatom affects aggregation. In the treatments with the natural phytoplankton, a significant effect of temperature on aggregation was detected only in the late bloom, when the aggregate area increased at 11uC relative to 6uC. In contrast, in the T. rotula–supplemented treatments, aggregation was enhanced by the elevated temperature at the peak but not in the late bloom. The aggregate area per microgram particulate organic carbon, a normalized measure to assess the aggregation potential, indicated that the aggregation potential in the natural phytoplankton community decreased from the peak to the late bloom, independent of temperature. This was presumably due to the reduced stickiness of the particles and lower concentrations of transparent exopolymer particles in the late phase. In the T. rotula–supplemented treatments, aggregation potential increased from the peak to the late bloom at the ambient temperature, whereas it decreased at the elevated temperature. Flavobacteria and Sphingobacteria of the Bacteroidetes phylum and Gammaproteobacteria were the dominant bacterial groups colonizing the aggregates.
Limnology and Oceanography 11/2014; 59(6):2089–2100. DOI:10.4319/lo.2014.59.6.2089 · 3.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Seawater circulation in permeable coastal sediments is driven by tidal changes in hydraulic gradients. The resulting submarine groundwater discharge is a source of nutrients and dissolved organic matter (DOM) to the water column. Yet, little is known about the cycling of DOM within tidal sediments, because the molecular DOM characterization remains analytically challenging. One technique that can dissect the multitude of molecules in DOM is ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). To aim at a high resolution DOM analysis we study the seasonal turnover and marine and terrestrial sources of DOM in an intertidal creek bank of the southern North Sea down to 3 m depth and link the biogeochemical processes to FT-ICR-MS data and the analyses of inorganic porewater chemistry, δ13C of solid-phase extracted dissolved organic carbon (SPE-DOC), dissolved black carbon (DBC) and dissolved carbohydrates (DCHO). Increasing concentrations of dissolved Fe, Mn, P, total alkalinity, dissolved nitrogen, DOC and a concomitant decrease of sulfate along the seawater circulation path from the upper tidal flat to the tidal flat margin indicate continuous microbial activity. The relative increase of Si concentrations, unsaturated aliphatics, peptide molecular formulae and isotopically more 13C-enriched SPE-DOC towards the tidal flat margin suggests that remineralization processes mobilize DOM from buried algal (diatoms) and microbial biomass. Porewater in sediments <100 cm depth contains 13C-depleted SPE-DOC and highly unsaturated compounds which are probably derived from eroded peats, suggesting rapid removal of bioavailable marine DOM such as DCHO from the water column and selective enrichment of terrestrial DOM. DBC concentrations are highest in the discharging porewater close to the tidal creek suggesting that the intertidal flat is an important DBC source to the coastal ocean. Porewater DOM accumulating at the low water line is enriched in N and S. We hypothesize that this is partly due to DOM reacting with dissolved sulfide and ammonium which may increase the refractory character of the DOM, hence making it less bioavailable for in situ active microbes.
[Show abstract][Hide abstract] ABSTRACT: The RCA (Roseobacter clade affiliated) cluster, with an internal 16S rRNA gene sequence similarity of >98%, is the largest cluster of the marine Roseobacter clade and most abundant in temperate to (sub)polar oceans, constituting up to 35% of total bacterioplankton. The genome analysis of the first described species of the RCA cluster, Planktomarina temperata RCA23, revealed that this phylogenetic lineage is deeply branching within the Roseobacter clade. It shares not >65.7% of homologous genes with any other organism of this clade. The genome is the smallest of all closed genomes of the Roseobacter clade, exhibits various features of genome streamlining and encompasses genes for aerobic anoxygenic photosynthesis (AAP) and CO oxidation. In order to assess the biogeochemical significance of the RCA cluster we investigated a phytoplankton spring bloom in the North Sea. This cluster constituted 5.1% of the total, but 10-31% (mean 18.5%) of the active bacterioplankton. A metatranscriptomic analysis showed that the genome of P. temperata RCA23 was transcribed to 94% in the bloom with some variations during day and night. The genome of P. temperata RCA23 was also retrieved to 84% from metagenomic data sets from a Norwegian fjord and to 82% from stations of the Global Ocean Sampling expedition in the northwestern Atlantic. In this region, up to 6.5% of the total reads mapped on the genome of P. temperata RCA23. This abundant taxon appears to be a major player in ocean biogeochemistry.The ISME Journal advance online publication, 1 August 2014; doi:10.1038/ismej.2014.134.
The ISME Journal 08/2014; 9(2). DOI:10.1038/ismej.2014.134 · 9.30 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Heterotrophic bacterial communities are major drivers of organic matter remineralization in the World’s Oceans. As much of organic matter consists of polymers, investigating the hydrolytic potential among marine bacteria is crucial for the understanding of marine nutrient cycles and their linkages with bacterial community structure. The present study characterized the response of bacterioplankton communities to polymeric carbohydrates at four locations in the Southern and Atlantic Oceans using natural seawater microcosms amended with chitin, alginate, and agarose. Cell numbers as determined by flow cytrometry increased markedly in temperate water microcosms (Patagonian Shelf), yielding almost double cell numbers with alginate and chitin compared to the control regime (3 × 106 cells mL-1). In warm water microcosms (Mauritanian Upwelling), only alginate distinctly stimulated bacterial growth, yielding almost double cell numbers (2.3 × 106 cells mL-1). Cell numbers remained almost unchanged in polar water microcosms (Polar Front, Antarctic Ice Shelf). 454 pyrosequencing as well as CARD-FISH revealed that Gammaproteobacteria were significantly stimulated across all locations and regimes (p < 0.05). Agarose and alginate strongly stimulated Alteromonadaceae in temperate waters, reaching relative abundances of 63 and 78%, respectively. This was largely due to single OTUs related to Pseudoalteromonas atlantica and Alteromonas macleodii, respectively. The response of Colwellia was determined by both location and substrate, being stimulated by agarose and alginate in polar waters and by chitin at all locations except the Antarctic Ice Shelf. The latter instead featured a significant stimulation of Fibrobacteres (reaching 28%). Chitin strongly stimulated Reichenbachiella (Cytophagales) in polar and temperate waters, with relative abundances increasing by 300- to 1500-fold (p < 0.005). At present, several alginate-degrading strains from the Gammaproteobacteria and Bacteroidetes are investigated by physiological and whole-genome analyses, indicating that closely related strains have distinct alginate utilization modes. In conclusions, this study presents a comprehensive picture of bacterial polysaccharide degradation in different oceanic regions and contributes to the understanding of fundamental marine nutrient cycles across wide geographical scales.
Gordon Research Conference ‘Marine Microbes’ and ISME-15, Bentley, USA / Seoul, Korea; 06/2014
[Show abstract][Hide abstract] ABSTRACT: In order to examine the specific role of diatoms in cycling of the trace metals manganese (Mn), molybdenum (Mo), vanadium (V), and uranium (U) Thalassiosira rotula, Skeletonema marinoi, Chaetoceros decipiens, and Rhizosolenia setigera were grown in batch cultures axenically and inoculated with three different bacterial strains isolated from the North Sea. Algal and bacterial growth, concentrations of trace metals and dissolved organic carbon (DOC) were monitored over time and showed that Mn and V were removed from the dissolved phase whereas Mo and U were not. R. setigera and T. rotula exhibited lowest growth and lowest removal whereas S. marinoi grew best and removed highest fractions of Mn and V. The high potential of Mn removal by S. marinoi was also evident from its 7x higher Mn/P elemental ratio relative to T. rotula. The presence of bacteria modified the timing of the growth of S. marinoi but not directly trace metal removal whereas bacteria enhanced trace metal removal in the cultures of T. rotula and C. decipiens. Modeling of phytoplankton growth, concentrations of Mn and DOC fraction in axenic T. rotula cultures indicated that processes of binding and desorption of Mn to excreted organic components are important to explain the varying proportions of dissolved Mn and thus must be considered as an active component in Mn cycling. The results show distinct differences in the potential of the diatoms in removal of Mn and V and that bacteria can play an active role in this context. S. marinoi presumably is an important player in Mn and V dynamics in coastal marine systems.
Journal of Sea Research 03/2014; 87:35-45. DOI:10.1016/j.seares.2013.09.009 · 1.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Leisingera nanhaiensis DSM 24252T is a Gram-negative, motile, rod-shaped marine Alphaproteobacterium, isolated from sandy marine sediments. Here we present the non-contiguous genome sequence and annotation together with a summary of the organism's phenotypic features. The 4,948,550 bp long genome with its 4,832 protein-coding and 64 RNA genes consists of one chromosome and six extrachromosomal elements with lengths of 236 kb, 92 kb, 61 kb, 58 kb, 56 kb, and 35 kb, respectively. The analysis of the genome showed that DSM 24252T possesses all genes necessary for dissimilatory nitrite reduction, and the strain was shown to be facultatively anaerobic, a deviation from the original description that calls for an emendation of the species. Also present in the genome are genes coding for a putative prophage, for gene-transfer agents and for the utilization of methylated amines. Phylogenetic analysis and intergenomic distances indicate that L. nanhaiensis might not belong to the genus Leisingera.
Standards in Genomic Sciences 01/2014; DOI:10.4056/sigs.3828824 · 3.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Strain T5(T) is the type strain of the species Phaeobacter inhibens Martens et al. 2006, a secondary metabolite producing bacterium affiliated to the Roseobacter clade. Strain T5(T) was isolated from a water sample taken at the German Wadden Sea, southern North Sea. Here we describe the complete genome sequence and annotation of this bacterium with a special focus on the secondary metabolism and compare it with the genomes of the Phaeobacter inhibens strains DSM 17395 and DSM 24588 (2.10), selected because of the close phylogenetic relationship based on the 16S rRNA gene sequences of these three strains. The genome of strain T5(T) comprises 4,130,897 bp with 3.923 protein-coding genes and shows high similarities in genetic and genomic characteristics compared to P. inhibens DSM 17395 and DSM 24588 (2.10). Besides the chromosome, strain T5(T) possesses four plasmids, three of which show a high similarity to the plasmids of the strains DSM 17395 and DSM 24588 (2.10). Analysis of the fourth plasmid suggested horizontal gene transfer. Most of the genes on this plasmid are not present in the strains DSM 17395 and DSM 24588 (2.10) including a nitrous oxide reductase, which allows strain T5(T) a facultative anaerobic lifestyle. The G+C content was calculated from the genome sequence and differs significantly from the previously published value, thus warranting an emendation of the species description.
[Show abstract][Hide abstract] ABSTRACT: TF-218(T) is the type strain of the species Phaeobacter daeponensis Yoon et al. 2007, a facultatively anaerobic Phaeobacter species isolated from tidal flats. Here we describe the draft genome sequence and annotation of this bacterium together with previously unreported aspects of its phenotype. We analyzed the genome for genes involved in secondary metabolite production and its anaerobic lifestyle, which have also been described for its closest relative Phaeobacter caeruleus. The 4,642,596 bp long genome of strain TF-218(T) contains 4,310 protein-coding genes and 78 RNA genes including four rRNA operons and consists of five replicons: one chromosome and four extrachromosomal elements with sizes of 276 kb, 174 kb, 117 kb and 90 kb. Genome analysis showed that TF-218(T) possesses all of the genes for indigoidine biosynthesis, and on specific media the strain showed a blue pigmentation. We also found genes for dissimilatory nitrate reduction, gene-transfer agents, NRPS/ PKS genes and signaling systems homologous to the LuxR/I system.
[Show abstract][Hide abstract] ABSTRACT: Despite their importance for ecosystem functioning, little is known about the composition of active marine bacterioplankton communities. Hence, this study was focused on assessing the diversity of these communities in the southern North Sea and examining the impact of a phytoplankton spring bloom on the ambient bacterioplankton community. Community composition in and outside the bloom was assessed in 14 samples by pyrosequencing-based analysis of 16S rRNA amplicons generated from environmental RNA. The dataset comprised 211,769 16S rRNA sequences. Proteobacteria were the predominant phylogenetic group with Alphaproteobacteria and Gammaproteobacteria as the most abundant classes. Actinobacteria and Bacteroidetes were identified in minor abundances. Active bacterial communities were dominated by few lineages such as the Roseobacter RCA cluster and the SAR92 clade. Community structures of three selected samples were also assessed by direct sequencing of cDNA generated from rRNA-depleted environmental RNA. Generated datasets comprised 988,202 sequences. Taxonomic assignment of the reads confirmed the predominance of Proteobacteria. The phytoplankton spring bloom affected the bacterioplankton community structures significantly. Bacterial richness was reduced in the bloom area and the abundance of certain bacterial groups was affected by bloom presence. The SAR92 clade and the Roseobacter RCA cluster were significantly more abundant and active in the bloom. Functions affected by the bloom include photosynthesis, protein metabolism, and DNA metabolism. This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: In 2009 Phaeobacter caeruleus was described as a novel species affiliated with the marine Roseobacter clade, which, in turn, belongs to the class Alphaproteobacteria. The genus Phaeobacter is well known for members that produce various secondary metabolites. Here we report of putative quorum sensing systems, based on the finding of six N-acyl-homoserine lactone synthetases, and show that the blue color of P. caeruleus is probably due to the production of the secondary metabolite indigoidine. Therefore, P. caeruleus might have inhibitory effects on other bacteria. In this study the genome of the type strain DSM 24564(T) was sequenced, annotated and characterized. The 5,344,419 bp long genome with its seven plasmids contains 5,227 protein-coding genes (3,904 with a predicted function) and 108 RNA genes.
[Show abstract][Hide abstract] ABSTRACT: Four heterotrophic bacterial strains belonging to the globally distributed marine RCA (Roseobacter Clade Affiliated) cluster (family Rhodobacteraceae, class Alphaproteobacteria) were obtained from coastal seawater samples. Strain RCA23T was isolated from a 10-7 dilution culture inoculated with seawater from the German Wadden Sea (southern North Sea), reflecting the high abundance of RCA bacteria in this habitat. Strains IMCC1909, IMCC1923 and IMCC1933 were isolated from diluted seawater (10-3) of the Yellow Sea, South Korea. Based on 16S rRNA gene sequence comparison, Octadecabacter antarcticus strain 307T is the closest described relative of the RCA strains, with 95.4 to 95.5 % sequence similarity. Cells of RCA23T, IMCC1909, IMCC1923 and IMCC1933 are small motile rods requiring sodium ions. Optimal growth of RCA23T occurs at 25 °C and within a very narrow pH range (7 to 8, optimum 7.5). The DNA G+C base composition of RCA23T is 53.67 %. The major respiratory lipoquinone is ubiquinone-10 (Q-10) and the dominant fatty acids (>1%) are 12:1 3OH, 16:1 ω7c, 16:0, 18:1 ω7c, 18:0 and 11 methyl 18:1 ω7c. The polar lipid pattern indicated presence of phosphatidylglycerol, two unidentified aminolipids and two unidentified phospholipids. On marine agar RCA23T forms non-pigmented, transparent to light beige, small (<1 mm), circular, convex colonies. Strain RCA23T harbors all genes for the production of bacteriochlorophyll a (BChl a). Genes encoding the light-harvesting reaction center of BChl a (pufM) were identified in all RCA strains. No visible pigmentation was observed for any of the strains under laboratory conditions, but spectrophotometric analysis revealed a weak production of BChl a by RCA23T. Morphological, physiological and genotypic features of strain RCA23T suggest that it represents a novel species of a novel genus within the Rhodobacteraceae, for which we propose the name Planktomarina temperata gen. nov., sp. nov., previously described as Candidatus Planktomarina temperata by Giebel et al. (2011). The type strain of the type species is RCA23T (= DSM 22400T = JCM 18269T).
International Journal of Systematic and Evolutionary Microbiology 06/2013; 63(Pt 11). DOI:10.1099/ijs.0.053249-0 · 2.51 Impact Factor