Thalassospira lucentensis gen. nov., sp. nov., a new marine member of the alpha-Proteobacteria.
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A novel bacterium from the Mediterranean Sea was isolated under oligotrophic conditions at in situ temperature after prolonged continuous culture. The isolates were initially characterized by partial 16S rRNA gene sequencing. Similarity searches of one of the isolates, QMT2T, indicated high sequence identity to the well-characterized Rhodospirillum rubrum, [Aquaspirillum] itersonii and [Oceanospirillum] pusillum micro-organisms, which are representatives of the alpha-subclass of the Proteobacteria. The highest level of similarity of the complete 165 rRNA gene with respect to these microorganisms was 89%. Features such as the low similarities of 165 rRNA of QMT2T with its phylogenetically close neighbours, the distinct G+C content, and the differences in phenotypic features, including pigmentation, fatty acid composition, salt tolerance, the lack of bacteriochlorophyll a, and the capacity to use carbohydrates as carbon sources, are indicative of the novel nature of the isolate QMT2T among the alpha-Proteobacteria. This report describes the classification of strain QMT2T (= DSM 14000T = CECT 5390T) as a new genus and species, Thalassospira lucentensis gen. nov, sp. nov., in the family Rhodospirillaceae. (+info)
Gelidibacter mesophilus sp. nov., a novel marine bacterium in the family Flavobacteriaceae.
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Two Gram-negative, aerobic, heterotrophic, marine bacteria, isolated from Mediterranean sea water off the coast near Valencia (Spain), were the object of this study. These non-motile, yellow-pigmented, rod-shaped strains have been studied by means of DNA-DNA hybridization, 16S rRNA sequencing and cultural and physiological features. Phylogenetic analysis showed that both strains belong to the phylum Cytophaga-Flavobacterium-Bacteroides, and their closest neighbour is the psychrophilic bacterium Gelidibacter algens. The two strains differ from G. algens in their mesophilic behaviour, hydrolytic pattern and use of different carbon sources. There is 31% DNA-DNA hybridization between the proposed type strain and G. algens, and both isolates show 97.5% 16S rDNA similarity to G. algens. They represent a novel species of the genus Gelidibacter, for which the name Gelidibacter mesophilus sp. nov. is proposed, with strain 2SM29T (= CECT 5103T = DSM 14095T) as the type strain. (+info)
Posidonia oceanica meadow: a low nutrient high chlorophyll (LNHC) system?
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BACKGROUND: In spite of very low nutrient concentrations in its vicinity - both column and pore waters-, the Posidonia oceanica of the Revellata Bay displays high biomass and productivity. We measured the nutrient fluxes from the sediment into the water enclosed among the leaf shoots ("canopy water") to determine if it is possible source of nutrients for P. oceanica leaves. RESULTS: During the summer, the canopy water appears to act as a nutrient reservoir for the plant. During that period, the canopy water layer displays both a temperature 0.5 degrees C cooler than the upper water column, and a much higher nutrient content, as shown in this work using a very simple original technique permitting to sample water with a minimal disturbance of the water column's vertical structure. Despite low nutrient concentrations in pore water, mean net fluxes were measured from the sediment to the canopy water. These fluxes are sufficient to provide 20% of the mean daily nitrogen and phosphorus requirement of the P. oceanica shoots. CONCLUSION: An internal cycling of nutrients from P. oceanica senescent leaves was previously noted as an efficient strategy to help face low nutrient availability. The present study points out a second strategy which consists in holding back, in the canopy, the nutrients released at the water-sediment interface. This process occurs when long leaves, during poor nutrient periods in the water column, providing, to P. oceanica, the possibility to develop, high biomass, high chlorophyll quantities in low nutrient environment (a Low Nutrients High Chlorophyll system). (+info)
Erythrobacter citreus sp. nov., a yellow-pigmented bacterium that lacks bacteriochlorophyll a, isolated from the western Mediterranean Sea.
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Two facultatively oligotrophic, intensely yellow-pigmented bacterial strains, RE35F/1T and RE10F/45, have been previously isolated from the western Mediterranean Sea (Bay of Calvi, Corsica, France) by 0.2 microm membrane filtration. The organisms were gram-negative, catalase- and oxidase-positive, strictly aerobic, rod-shaped and non-motile. Their respiratory lipoquinone profiles consisted exclusively of ubiquinone-10 (Q-10) and the G+C contents of their DNAs were 62.0 and 62.4 mol%, respectively. Among the cellular fatty acids, octadecenoic acid (18:1omega7c) was the major component. Both isolates also contained hydroxy fatty acids (14:0 2-OH, 18:1 2-OH and 16:0 iso 3-OH) and branched fatty acids (15:0 anteiso, 16:0 anteiso and 17:0 anteiso). Polar lipid fingerprints were characterized by the presence of a sphingoglycolipid. Comparative analyses of their 16S rRNA gene sequences indicated that both isolates were phylogenetically closely related (sequence similarity of 99.9%) and formed a coherent cluster with aerobic bacteriochlorophyll a-containing species of the Erythrobacter/Porphyrobacter/Erythromicrobium cluster within the family Sphingomonadaceae. The closest relative was Erythrobacter litoralis DSM 8509T (97.4 and 97.5% 16S rRNA gene sequence similarity between this strain and RE35F/1T and RE10F/45, respectively). DNA-DNA reassociation studies confirmed that strains RE35F/1T and RE10F/45 represent a single species (79.6% DNA homology), but also demonstrated that they do not belong to the species Erythrobacter litoralis (25.2 and 34.2% DNA homology, respectively). Notably, both RE35F/1T and RE10F/45 lacked bacteriochlorophyll a. Based upon phenotypic and molecular evidence, a novel species of the genus Erythrobacter, Erythrobacter citreus sp. nov., is proposed. Strain RE35F/1T (= CIP 107092T = DSM 14432T) is the type strain. (+info)
Extensive population subdivision of the cuttlefish Sepia officinalis (Mollusca: Cephalopoda) around the Iberian Peninsula indicated by microsatellite DNA variation.
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The Atlantic Ocean-Mediterranean Sea junction has been proposed as an important phylogeographical area on the basis of concordance in genetic patterns observed at allozyme, mtDNA and microsatellite DNA markers in several marine species. This study presents microsatellite DNA data for a mobile invertebrate species in this area, the cuttlefish Sepia officinalis, allowing comparison of this relatively new class of DNA marker with previous allozyme results, and examination of the relative effects on gene flow of the Strait of Gibraltar and the Almeria-Oran oceanographic front. Genetic variation at seven microsatellite loci screened in six samples from NE Atlantic and Mediterranean coasts of the Iberian Peninsula was high (mean Na = 9.6, mean H(e) = 0.725). Microsatellites detected highly significant subpopulation structuring (F(ST)= 0.061; R(ST) = 0.104), consistent with an isolation-by-distance model of low levels of gene flow. Distinct and significant clinal changes in allele frequencies between Atlantic and Mediterranean samples found at five out of seven loci, however indicate these results might be also consistent with an alternative model of secondary contact and introgression between previously isolated and divergent populations, as previously proposed for other marine species from the Atlantic-Mediterranean area. A pronounced 'step' change between SW Mediterranean samples associated with the Almeria-Oran front suggests this oceanographic feature may represent a contemporary barrier to gene flow. (+info)
Geographic structure in the European flat oyster (Ostrea edulis L.) as revealed by Microsatellite polymorphism.
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Genetic differentiation of the flat oyster (Ostrea edulis) was studied along the European coast, from Norway to the Black Sea, by means of variation at five microsatellite loci. The results show a mild but significant isolation-by-distance profile, a noticeable between-sample variance in expected heterozygosity, and a tendency for Atlantic populations to be less variable than Mediterranean ones. This does not provide support for the existence of a single large panmictic population for this larvae-broadcasting species, but rather for the relative independence of local stocks. Comparison with data on allozyme variation from the literature confirms this view. It also leads us to suggest that the behavior of some sampled protein loci may depart from the average, so caution should be used when inferring neutral gene flow. (+info)
Messinian salinity crisis and the origin of freshwater lifestyle in western Mediterranean gobies.
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The present paper reports on a molecular study based on 12S rRNA and 16S rRNA mitochondrial genes partly sequenced in 13 species of western Mediterranean gobies, three of which are strictly freshwater-dwelling. A total of 867 bp were aligned and used for the phylogenetic reconstruction. Two major lineages were identified, one clustering the sand gobies in a monophyletic clade. Relationships among taxa based on sequence analysis only partly match those based on morphological criteria, suggesting that the latter are somehow insufficient to correctly establish phylogenetic relationships within this family. The results provide evidence for a multiple independent evolution of the freshwater lifestyle in Knipowitschia and Padogobius lineages. On the basis of the present results, it is uncertain whether the freshwater preference within the genus Padogobius originated twice independently in P. nigricans and P. martensii or only once in their common ancestor. Estimation of the ages of the two major lineages of this group of fish with a molecular clock (in combination with the construction of a linearized tree) suggests that they are much older (at least 40 Myr) than previously thought. Thus, there should be no correlation between their diversification and the Miocene-Pliocene geological events, including the so-called Messinian salinity crisis, which occurred about 10 MYA and is believed to have played a role in their evolution. Alternatively, these gobies would have an evolutionary rate at least fourfold faster than those of other vertebrates. (+info)
Description of Alcanivorax venustensis sp. nov. and reclassification of Fundibacter jadensis DSM 1 21 78T (Bruns and Berthe-Corti 1999) as Alcanivorax jadensis comb. nov., members of the emended genus Alcanivorax.
(24/286)
Two strains of a novel bacterium were isolated independently of each other, from different depths in the Mediterranean Sea, within a time period of 7 months, using two different isolation approaches that were focused on different objectives. Both strains, designated ISO1 and ISO4T, were halophilic, Gram-negative, strictly aerobic, straight rods that were oxidase- and catalase-positive. Both strains produced mucoid colonies in some defined minimal media and were able to grow with organic acids and some alkanes; they were also able to accumulate intracellular poly-beta-hydroxybutyrate granules. The G + C content of the DNA of strain ISO4T was 66 mol%. Comparative analysis of 16S rRNA gene sequences showed that the closest described species to the novel strains were Alcanivorax borkumensis and Fundibacter jadensis, both of the gamma-Proteobacteria. Both of these recognized species were originally isolated from North Sea waters and are able to degrade aliphatic compounds, a property shared with strains ISO1 and ISO4T. However, strains ISO1 and ISO4T were different from A. borkumensis and F. jadensis, not only in their 16S rDNA sequences but also in the motility of their cells (by polar flagella) and by the presence of C19:Ocyclo in their cellular fatty acids, among other differential features. On the basis of biochemical and molecular data, it is suggested that strains ISO1 and ISO4T be recognized as a novel species of the genus Alcanivorax, for which the name Alcanivorax venustensis (ISO4T =DSM 13974T =CECT 5388T) is proposed. On the basis of its high phenotypic similarity and close phylogenetic relatedness to A. borkumensis, it is also proposed that F. jadensis (DSM 12178T) be reclassified as Alcanivorax jadensis in the genus Alcanivorax, and that the description of the genus Alcanivorax be emended. (+info)