A deep-sea bacterium related to coastal marine pathogens

Evolution of virulence traits from adaptation to environmental niches other than the host is probably a common feature of marine microbial pathogens, whose knowledge might be crucial to understand their emergence and pathogenetic potential. Here, we report genome sequence analysis of a novel marine bacterial species, Vibrio bathopelagicus sp. nov., isolated from warm bathypelagic waters (3309 m depth) of the Mediterranean Sea. Interestingly, V. bathopelagicus sp. nov. is closely related to coastal Vibrio strains pathogenic to marine bivalves. V. bathopelagicus sp. nov. genome encodes genes involved in environmental adaptation to the deep-sea but also in virulence, such as the R5.7 element, MARTX toxin cluster, Type VI secretion system and zinc-metalloprotease, previously associated with Vibrio infections in farmed oysters. The results of functional in vitro assays on immunocytes (haemocytes) of the Mediterranean mussel Mytilus galloprovincialis and the Pacific oyster Crassostrea gigas, and of the early larval development assay in Mytilus support strong toxicity of V. bathopelagicus sp. nov. towards bivalves. V. bathopelagicus sp. nov., isolated from a remote Mediterranean bathypelagic site, is an example of a planktonic marine bacterium with genotypic and phenotypic traits associated with animal pathogenicity, which might have played an evolutionary role in the origin of coastal marine pathogens.     

A marine,psychrophilic bacterium of the bacteroidaceae type

A characterization is presented of three strains of bacteria of the bacteroidaceae type, isolated at different times from different samples of fish (capelin) caught in far northern waters, and subsequently stored anaerobically at chill temperatures. The three strains have so many properties in common that they should be considered of the same taxon at the species level. The special feature of the organism that makes it different from all bacteroidaceae, described until now, is first of all its psychrophilic character. The optimum growth temperature is near 15°C, whereas the common bacteriodaceae are listed to have an optimum temperature near 37°C. The new organism is rapidly killed at the latter temperature; at killing temperatures a rupture of the cell envelope takes place. A specific requirement for NaCl supports the notion that the organism is indigenous to the marine environment, and is credibly an inhabitant of the gastrointestinal tract of marine fishes. It needs an almost strict anaerobic environment for growth, but seems able to survive for some time in the presence of air. The latter quality may help the organism to spread and colonize new anaerobic niches.Abbreviations CFU colony forming units - GC content mol% G+C - PY peptone-yeast extract - PYG PY-glucose - PYT PY-threonine - PYL PY-lactate - ESC extract of spoiling capelin Dedicated to Professor Dr. H.-G. Schlegel on the occasion of his 60th birthday     

A new extremely thermophilic,sulfur-reducing heterotrophic,marine bacterium

An extremely thermophilic (optimum growth at 88° C), anaerobic bacterium was isolated from a shallow submarine thermal spring. It appears to be an obligate heterotroph, capable of reducing sulfur to H₂S. Oxygen sensitivity is apparent only at and above those temperatures where growth occurs, while the cultures retain their viability for long periods under air at 4° C. Insensitivity to chloramphenicol, vancomycin and streptomycin, and lack of muramic acid in its cell wall, indicate a possible affilitation of the new isolate to the thermoacidophilic archaebacteria. However, its neutrophilic and hetertrophic nature, as well as its DNA base composition (39.1 mol % guanine plus cytosine) set it apart from the known genera of this group.Abbreviations ASW Artifical sea water medium - Bis-tris propane 1,3-bis[tris(hydroxymethyl)-methylamino]-propane - Mes 2(N-morpholino)ethanesulfonic acid - Pipes Piperazine-N,N-bis(2-ethanesulfonic acid)     

A novel marine bacterium algicidal to the toxic dinoflagellate Alexandrium tamarense

Aims: This work is aiming at investigating algicidal characterization of a bacterium isolate DHQ25 against harmful alga Alexandrium tamarense. Methods and Results: 16S rDNA sequence analysis showed that the most probable affiliation of DHQ25 belongs to the γ‐proteobacteria subclass and the genus Vibrio. Bacterial isolate DHQ25 showed algicidal activity through an indirect attack. Xenic culture of A. tamarense was susceptible to the culture filtrate of DHQ25 by algicidal activity assay. Algicidal process demonstrated that the alga cell lysed and cellular substances released under the visual field of microscope. DHQ25 was a challenge controller of A. tamarense by the above characterizations of algicidal activity assay and algicidal process. Conclusion: Interactions between bacteria and harmful algal bloom (HAB) species proved to be an important factor regulating the population of these algae. Significance and Impact of Study: This is the first report of a Vibrio sp. bacterium algicidal to the toxic dinoflagellate A. tamarense. The findings increase our knowledge of the role of bacteria in algal–bacterial interaction.     

A marine bacterium producing protein with algicidal activity against Alexandrium tamarense

Interactions between bacteria and harmful algal bloom (HAB) species have been acknowledged as an important factor of regulating the population of these algae. In the study, two strains of algicidal bacteria, DHQ25 and DHY3, were screened out because of their probably secreting algicidal proteins against axenic Alexandrium tamarense. Molecular characterization classified them to the γ-proteobacteria subclass and to the genus Vibrio and Pseudoalteromonas, respectively. After centrifugation and ultrafiltration, chromatography of the cultural supernatants of DHQ25 revealed 8 peaks by HPLC. SDS-PAGE and Native PAGE determination showed that peak 7 to be a monoband peak. Both xenic and axenic culture of A. tamarense were susceptible to the purified protein (short for P7 below) indicated by algicidal activity assay. Observation of algicidal process demonstrated that algal cells were lysed and cellular substances were released under visual fields of microscope. P7 proved to be a challenge controller of A. tamarense by the above characterizations of algicidal activity assaying and algicidal process. This is the first report of a protein algicidal to the toxic dinoflagellate A. tamarense. The findings increase our knowledge of bacterial–algal interactions and the role of bacteria during controlling HABs.     

A pseudoaminic acid-containing O-specific polysaccharide from a marine bacterium Cellulophaga fucicola

The O-polysaccharide was isolated from the lipopolysaccharide of Cellulophaga fucicola and studied by chemical analyses along with (1)H and (13)C NMR spectroscopy. The following new structure of the O-polysaccharide of C. fucicola containing 5,7-diacetamido-3,5,7,9-tetradeoxy-L-glycero-L-manno-non-2-ulosonic acid residue (pseudoaminic acid, Psep) was elucidated as the following:     

Lipids of the marine bacterium Flexibacter polymorphus

This paper reports on the total fatty acid composition of a marine bacterium representative of the genus Flexibacter. Flexibacter polymorphus is unusual in containing a high proportion of the polunsaturated acid C20:53 whilst the level of branched fatty acids is low. These facts suggest that the membrane flexibility necessary for its gliding motility is a function of the polyunsaturated fatty acid composition. Biosynthetic precursors to the C20:5 acid are present which are characteristic of an oxygen-dependent pathway. The fatty acid composition of the structural lipids is influenced by changes in the culture medium. Na₂S inhibits production of the C20:5 acid at levels much lower than that at which it is known to inhibit growth. The intracellular granules observable in F. polymorphus do not contain elemental sulphur, in contrast to Beggiatoa sps., but instead probably contain lipids.     

Pleomorphism of the marine bacterium Teredinobacter turnirae

AIMS: A morphology transition for the marine bacterium, Teredinobacter turnirae is reported. METHODS AND RESULTS: When grown in the rod-shaped morphology, the cells require high concentrations of NaCl (0.3 mol x l(-1)) and secrete extracellular protease and endoglucanase activity. When this bacterium is grown in a medium containing casein as a sole carbon and nitrogen source, a major change in morphology to a stable aggregated form is obtained. CONCLUSION: In the aggregated morphology, much higher protease production rates (170 Units x ml(-1) x d-1 for aggregates vs. 15 Units x ml(-1) x d(-1) for rods, for the same initial biomass) and negligible endoglucanase titres are obtained. In addition, the aggregated morphology does not require sodium chloride for growth. SIGNIFICANCE AND IMPACT OF THE STUDY: The phenomenon reported here describes a novel relationship between the cell morphology and the biochemical characteristics of the bacterium.     

Hydrocarbon metabolism in a marine bacterium]

The marine bacterium L.16.1 (Alcaligenes sp.) grows preferentially on alkanes (C10 to C18) with a very high growth yield (98 per cent); optimal growth depends strictly on the presence of a well-defined NaCl concentration (100 mM). Our strain is constitutive for the enzymatic systems responsible for the oxidation of alkanes to fatty acids, i.e. NADH-dependent hydroxylase, alcohol and aldehyde dehydrogenases, the latter of which located at the cytoplasmic membrane level. The aerobic oxidation of primary alcohols by particulate extracts prepared in the presence of 400 mM NaCl is NAD+-dependent (Km = 0.082 mM, Vmax = 238 with decanol). With extracts prepared in the absence of NaCl, Vmax undergoes a very strong decrease. On the contrary , the NAD+ (P)+-dependent oxidation of aldehydes is carried out anaerobically by the same extracts irrespective of the presence or the absence of added Na+ in the solutions used for the preparation of these extracts. A possible explanation for our results could be that Na+ acts on the enzymatic systems for which the maintenance of the membrane integrity is essential. This interpretation is consistent with the slowing down of the growth speed accompanying the decrease of NaCl concentration in the growth medium. With regard to alcohol and aldehyde-dehydrogenases, it is noteworthy that these enzymes behave like similar enzymatic activities induced by alkanes in other microorganisms.     

ATP hydrolysis in a marine bacterium.

The membrane-bound adenosine triphosphatase of marine pseudomonad B-16, when solubilized, is able to rebind to depleted membrane residues of the bacterium and to those of Escherichia coli.     

海洋细菌Pseudomonas putida中具有抗硅藻附着的活性成分

【目的】为发现天然的防污损物质,从分离自海绵Haliclona sp.的细菌Pseudomonas putida中寻找具有抗硅藻附着活性的化合物。【方法】综合菌落生长形态、扫描电镜及16S rDNA序列分析,鉴定细菌种属;采用活性(抗硅藻附着)-化学(薄层色谱、二极管阵列高效液相和核磁共振氢谱)导向法对其中的活性组分进行分离纯化,波谱分析确定结构;采用抗硅藻附着活性模型对单体化合物进行活性复筛。【结果】该细菌鉴定为Pseudomonas putida;从其发酵液中分离得到6个环二肽,分别鉴定为环(亮氨酸-脯氨酸)(1)、环(亮氨酸-丙氨酸)(2)、环(苯丙氨酸-丙氨酸)(3)、环(缬氨酸-酪氨酸)(4)、环(丙氨酸-酪氨酸)(5)、环(丙氨酸-色氨酸)(6);化合物3和6在浓度为50μg/mL时具有明显的抑制硅藻附着活性(抑制率分别为50%和85%)。【结论】海洋细菌Pseudomonas putida中具有抗硅藻附着的活性化合物为环(苯丙氨酸-丙氨酸)和环(丙氨酸-色氨酸)。     

A cold-adapted epoxide hydrolase from a strict marine bacterium, Sphingophyxis alaskensis

An open reading frame (ORF) encoding a putative epoxide hydrolase (EHase) was identified by analyzing the genome sequence of Sphingophyxis alaskensis. The EHase gene (seh) was cloned and expressed in E. coli. To facilitate purification, the gene was fused in-frame to 6x histidine at the C-terminus. The recombinant EHase (rSEH) was highly soluble and could be purified to apparent homogeneity by one step of metal affinity chromatography. The purified SEH displayed hydrolyzing activities toward various epoxides such as styrene oxide, glycidyl phenyl ether, epoxyhexane, epoxybutane, epichlorohydrin, and epifluorohydrin. The optimum activity toward styrene oxide was observed at pH 6.5 and 35 degrees . The purified SEH showed a coldadapted property, displaying more than 40% of activity at low temperature of 10 degrees compared with the optimum activity. Despite the catalytic efficiency, the purified SEH did not hydrolyze various epoxides enantioselectively. Km and kcat of SEH toward (R)-styrene oxide were calculated as 4+/-0.3 mM and 7.42 s-1, respectively, whereas Km and kcat of SEH toward (S)-styrene oxide were 5.25+/-0.3 mM and 10.08 s-1, respectively.     

A novel,symbiotic bacterium isolated from marine shipworm secretes proteolytic activity

Proteolytic activity was identified in cultures of the marine shipworm bacterium by monitoring of the release of acid-soluble azopeptides from azocasein. Activity was predominantly extracellular (>80%), and its production was coincident with logarithmic cell growth. The protease(s) appeared to be constitutive, since it was present even when the bacterium was grown under nitrogen-fixing conditions. However, activity was stimulated up to 8.6-fold by the addition of complex nitrogen (casein, amino acids) to the growth medium. Maximum activity was observed at 40°C and between pH 6.5 and 9.0. Relatively low concentrations (0.1 mM) of phenylmethylsulfonyl fluoride (PMSF) abolished activity, indicative of a serine protease(s).The mention of firm names or trade products does not imply that they are endorsed or recommended by the US Department of Agriculture over other firms or similar products not mentioned.     

Total energy flux in a marine bioluminescent bacterium

Abstract The total heat production from luminous bacteria growing on glycerol as a sole source of carbon and energy was measured in an isothermal microcalorimeter and compared to the light emitted and growth yield. Substrate concentration was measured before and after growth to calculate the amount of substrate utilized. From these data the total energy flux was determined for Vibrio harveyi : a 25 ml culture consumed 328 micromoles of glycerol (130 cal) and produced 54 calories of heat, 76.3 cal of biomass, and 3.5 millicalories of light. Bioluminescence was then only a very small fraction (0.007%) of the total energy expended.     

Sodium ion-proton antiport in a marine bacterium.

Alteromonas haloplanktis ejected protons in response to a brief respiratory pulse; the rate of decay of the resulting pH change was accelerated when Na+ was present in the suspension medium. The addition of an anaerobic NaCl solution to an essentially Na+-free anaerobic bacterial suspension induced the acidification of the suspension medium. These results and others discussed provide substantial evidence for the existence of an Na+-H+ antiporter in this organism.     

Novel epibiotic thiothrix bacterium on a marine amphipod

Comparative analysis of the 16S rRNA gene and fluorescent in situ hybridization (FISH) was used to identify epibiotic filamentous bacteria living on the marine amphipod crustacean Urothoe poseidonis. The epibionts belong to the gamma proteobacteria and represent a novel marine phylotype within the genus Thiothrix. FISH and denaturing gradient gel electrophoresis revealed that the Thiothrix filaments are present on the majority of the amphipods examined.     

The smallest ssDNA phage infecting a marine bacterium

In the marine environment, only a few lytic single-stranded DNA (ssDNA) phages have been isolated and characterized, despite the fact that diverse ssDNA bacteriophages have been discovered via metagenomic studies. In this study, we isolated and characterized a new ssDNA phage, vB_RpoMi-Mini, which infects a marine bacterium Ruegeria pomeroyi DSS-3. With a genome size of 4248 bp and only four putative open reading frames (ORF), vB_RpoMi-Mini becomes the smallest ssDNA phage among the known ssDNA phage isolates and represents the DNA bacteriophage with the least number of ORFs. Genome-wide analysis reveals that bacteriophage Mini is distantly related to the known ssDNA phages and belongs to an unclassified ssDNA phage within the Microviridae family. The presence of peptidase in vB_RpoMi-Mini genome further implies that horizontal gene transfer could be an important driving force in the evolution of ssDNA phages. Bacteriophage Mini seems to have lost the spike protein commonly seen in ssDNA phages, suggesting that ssDNA phage can be more diverse than previously thought. Metagenomic analysis indicates that Mini-like phages are widely distributed in the environments. The discovery of vB_RpoMi-Mini expands our understanding of ssDNA phages in nature, and also indicates our dearth of knowledge regarding of ssDNA phages.