Thiocapsa marina sp. nov., a new purple sulfur bacterium containing okenone isolated from several brackish and marine environments

Four marine, phototrophic, purple sulfur bacteria (strains 5811T, 5812, BM-3 and BS-1) were isolated in pure culture from different brackish to marine sediments in the Mediterranean Sea, the White Sea and the Black Sea. Single cells of these strains were coccus-shaped, non-motile and did not contain gas vesicles. The colour of cell suspensions that were grown in the light was purple–red. Bacteriochlorophyll a and carotenoids of the okenone series were present as photosynthetic pigments. Photosynthetic membrane systems were of the vesicular type. Hydrogen sulfide, thiosulfate, elemental sulfur and molecular hydrogen were used as electron donors during photolithotrophic growth under anoxic conditions; carbon dioxide was utilized as the carbon source. During growth on sulfide, elemental sulfur globules were stored inside the cells. In the presence of hydrogen sulfide, several organic substances could be photoassimilated. Comparative 16S rDNA sequence analysis revealed an affiliation of these four strains to the genus Thiocapsa. Both phylogenetic analysis and the results of DNA–DNA hybridization studies revealed that these strains formed a separate cluster within the genus Thiocapsa. Thus, according to phenotypic characteristics and mainly the carotenoid composition, 16S rDNA sequence analysis and DNA–DNA hybridization data, it is proposed that these strains should be classified as a novel species, Thiocapsa marina sp. nov., with strain 5811T (=DSM 5653T=ATCC 43172T) as the type strain

Sulfide fluxes in a microbial mat from the Ebro Delta, Spain

The sulfur cycle of Ebro Delta microbial mats was studied in order to determine sulfide production and sulfide consumption. Vertical distribution of two major functional groups involved in the sulfur cycle, anoxygenic phototrophic bacteria and dissimilatory sulfate-reducing bacteria (SRB), was also studied. The former reached up to 2.2 ×108 cfu cm-3 sediment in the purple layer, and the latter reached about 1.8×105 SRB cm-3 sediment in the black layer. From the changes in sulfide concentrations under light-dark cycles it can be inferred that the rate of H2S production was 6.2 μmol H2S cm-3 day-1 at 2.6 mm, and 7.6 μmol H2S cm-3 day-1 at 6 mm. Furthermore, sulfide consumption was also assessed, determining rates of 0.04, 0.13 and 0.005 mmol l-1 of sulfide oxidized at depths of 2.6, 3 and 6 mm, respectively

Characterization of Desulfovibrio giganteus sp. nov., a sulfate-reducing bacterium isolated from a brackish coastal lagoon

In the course of ecological studies in Berre Lagoon, a mediterranean brackish coastal lagoon (Marseille, France), a new slightly halophilic sulfate-reducing bacterium was isolated from anoxic sediments enriched with lactate plus sulfate, and cysteine-HCL as reductant. Because of its morphology and the incomplete oxidation of organic substrates, the isolated strain 8601 was assigned to the genus #Desulfovibrio, resembling #Desulfovibrio gigas. However, it differed from this species in some morphological and physiological characteristics : only one polar flagellum the utilization of methanol, isopropanol, glycerol and cysteine as energy source. Therefore a new species #Desulfovibrio giganteus$ is described. (Résumé d'auteur

Distribution of phototrophic populations and primary production in a microbial mat from the Ebro Delta, Spain

Microbial mats arising in the sand flats of the Ebro Delta (Tarragona, Spain) were investigated during the summer season, when the community was highly developed. These mats are composed of three pigmented layers of phototrophic organisms, an upper brown layer mainly composed of Lyngbya aestuarii and diatoms, an intermediate green layer of the cyanobacterium Microcoleus chthonoplastes, and an underlying pink layer of a so-far unidentified purple sulfur bacterium. In the photic zone, oxygenic phototrophs constitute about 58% of total photosynthetic biomass, measured as biovolume, and anoxygenic phototrophs represent 42%. Diatoms constitute 11.8% of the oxygenic biomass, M. chthonoplastes 61.2%, and L. aestuarii and coccoid cyanobacteria 20.6 and 6.4%, respectively. In this laminated community, organic matter has an autochthonous origin, and photosynthesis is the most important source of organic carbon. Oxygen production reaches up to 27.2 mmol O2 m–2 h–1, measured at 1000 μE m–2 s–1 light intensity, whereas oxidation of sulfide in the light has been calculated to be 18.6 mmol S m–2 h–1. This amount represents 26% of the total photosynthetic production in terms of photoassimilated carbon, demonstrating the important role of anoxygenic phototrophs as primary producers in the pink layer of Ebro Delta microbial mats. [Int Microbiol 2004; 7(1):19–25

Taxonomic rearrangements of the genera Thiocapsa and Amoebobacter on the basis of 16S rDNA sequence analyses and description of Thiolamprovum gen. nov.

Complete nucleotide sequences of the 16S rDNAs were determined from Thiocapsa and Amoebobacter species, including all available type strains and some additional isolates. The distance-matrix analysis and the dendrogram for estimating the genetic relationships revealed that the investigated strains were found in two major clusters within the Chromatiaceae. One cluster comprises all Amoebobacter species, Thiocapsa roseopersicina and several isolates related to Thiocapsa roseopersicina. Representatives of the species Amoebobacter roseus, Amoebobacter pendens and Thiocapsa roseopersicina, the so called ‘Thiocapsa roseopersicina group’, are very closely related, justifying their inclusion into one genus, Thiocapsa, for which an emended description is presented. Amoebobacter purpureus and Amoebobacter pedioformis formed two separate lines of descent with less than 93% (89·6–92·9%) similarity to strains of the ‘Thiocapsa roseopersicina group’. Therefore, they will be considered as two separate genera. As a consequence, an emended description is presented for the genus Amoebobacter, with Amoebobacter purpureus as the new type species and A. pedioformis is transferred to Thiolamprovum pedioforme gen. nov., comb. nov. Two species, Thiocapsa pfennigii and Thiocapsa halophila, which have been classified with the genus Thiocapsa because of their morphological properties, were found within another major cluster of the Chromatiaceae and are only distantly phylogenetically related to the first cluster with 88·4–90·6% and 90·4–92·2% sequence similarity, respectively

<em>Marichromatium indicum</em> sp. nov., a new purple sulfur Gammaproteobacterium from mangroves of Goa, India

A reddish-brown bacterium was isolated from photoheterotrophic enrichments of mangrove soil from the western coast of India, in a medium that contained 10 % (w/v) NaCl. Phylogenetic analysis on the basis of 16S rRNA gene sequences showed that strain JA100T clusters with species of the genus Marichromatium of the class ‘Gammaproteobacteria’. Cells of strain JA100T are Gram-negative, motile rods with monopolar single flagella; they require NaCl, the optimum concentration being 1–4 %, and tolerate concentrations up to 13 %. The strain has vesicular internal membrane structures, bacteriochlorophyll a and, most probably, carotenoids of the spirilloxanthin series. No growth factors are required. A reduced sulfur source is required for growth, and, during growth on reduced sulfur sources as electron donors, sulfur is intermediately deposited as a single large granule within the cell. Strain JA100T could not grow at the expense of other tricarboxylic acid cycle intermediates, except malate. On the basis of 16S rRNA gene sequence analysis and its morphological and physiological characteristics, strain JA100T is sufficiently different from other Marichromatium species to justify its designation as a novel species, for which the name Marichromatium indicum sp. nov. is proposed. The type strain is JA100T (=DSM 15907T=ATCC BAA-741T=JCM 12653T)

Recommended standards for the description of new species of anoxygenic phototrophic bacteria

Recommended standards for the description of new species of the anoxygenic phototrophic bacteria are proposed in accordance with Recommendation 30b of the International Code of Nomenclature of Bacteria. These standards include information on the natural habitat, ecology and phenotypic properties including morphology, physiology and pigments and on genetic information and nucleic acid data. The recommended standards were supported by the Subcommittee on the taxonomy of phototrophic bacteria of the International Committee on Systematics of Prokaryotes. They are considered as guidelines for authors to prepare descriptions of new specie

Marichromatium bheemlicum sp. nov., a non-diazotrophic photosynthetic gammaproteobacterium from a marine aquaculture pond

A rod-shaped, phototrophic, purple sulfur bacterium, strain JA124(T), was isolated in pure culture from a marine aquaculture pond, located near Bhimunipatnam, in a medium that contained 3 % NaCl (w/v). Strain JA124(T) is a Gram-negative, motile rod with a single polar flagellum. Strain JA124(T) has a requirement for NaCl, with optimum growth at 1.5-8.5 %, and tolerates up to 11 % NaCl. Intracellular photosynthetic membranes are of the vesicular type. Bacteriochlorophyll a and probably carotenoids of the spirilloxanthin series are present as photosynthetic pigments. Strain JA124(T) was able to utilize sulfide, sulfate, thiosulfate, sulfite, thioglycollate and cysteine as sulfur sources. Strain JA124(T) was able to grow photolithoautotrophically, photolithoheterotrophically and photo-organoheterotrophically. Chemotrophic and fermentative growth could not be demonstrated. Strain JA124(T) lacks diazotrophic growth and acetylene reduction activity. Pyridoxal phosphate is required for growth. During growth on reduced sulfur sources as electron donors, sulfur is deposited intermediately as a number of small granules within the cell. Phylogenetic analysis on the basis of 16S rRNA gene sequences showed that strain JA124(T) clusters with species of the genus Marichromatium belonging to the class Gammaproteobacteria. The highest sequence similarities of strain JA124(T) were found with the type strains of Marichromatium indicum (98 %), Marichromatium purpuratum (95 %) and Marichromatium gracile (93 %). However, DNA-DNA hybridization with Marichromatium indicum DSM 15907(T) revealed relatedness of only 65 % with strain JA124(T). The DNA base composition of strain JA124(T) was 67 mol% G+C (by HPLC). Based on 16S rRNA gene sequence analysis, morphological and physiological characteristics and DNA-DNA hybridization studies, strain JA124(T) (=ATCC BAA-1316(T)=JCM 13911(T)) is sufficiently different from other Marichromatium species to merit its description as the type strain of a novel species, Marichromatium bheemlicum sp. nov