Emended description of the genus Rhodothalassium Imhoff et al., 1998 and proposal of Rhodothalassiaceae fam. nov. and Rhodothalassiales ord. nov.

Five strains (JA325, JA389, JA473, JA563 and JA582) of Gram stain-negative, vibrioid to spiral shaped, phototrophic purple bacteria were isolated from solar salterns of India. All strains contained bacteriochlorophyll-a and carotenoids of the spirilloxanthin series as photosynthetic pigments. C(18:1)ω7c, C(18:1)ω7c 11-methyl and C(16:0) were the major fatty acids of all strains. Diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), ornithine lipid (OL), an unidentified phospholipid (PL), and an unidentified aminolipid (AL) were the major polar lipids of all the strains. According to 16S rRNA gene sequences, all strains clustered phylogenetically with the only species of the genus Rhodothalassium (99.8-99.3% sequence similarity) but only strains JA325 and JA563 were distinctly related (60+1.5% DNA-DNA hybridization [DDH]) to the type strain Rhodothalassium salexigens DSM 2132(T). However, the genotypic data of strains JA325 and JA563 was not supported because of a large number of phenotypic differences compared to the type strain, therefore, it is proposed that all five newly isolated strains were R. salexigens-like strains. In addition, phylogenetically, the Rhodothalassium clade represented a distinct lineage and formed a deep branch with less than 90% 16S rRNA gene sequence similarity to other orders of the Alphaproteobacteria, and characteristic phenotypic properties also distinguished these bacteria from other purple non-sulfur bacteria. Therefore, the novel family Rhodothalassiaceae fam. nov. and the novel order Rhodothalassiales ord. nov. are proposed for the distinct phyletic line represented by the genus Rhodothalassium.

Rhodobacter johrii sp. nov., an endospore-producing cryptic species isolated from semi-arid tropical soils.

An oval to rod-shaped, phototrophic, purple non-sulfur bacterium, strain JA192(T), was isolated from an enrichment culture of a pasteurized rhizosphere soil sample from a field cultivated with jowar (sorghum) collected from Godumakunta village near Hyderabad, India. Strain JA192(T) is Gram-negative, motile and produces endospores. Phylogenetic analysis on the basis of 16S rRNA gene sequences showed that the strain JA192(T) is closely related to Rhodobacter sphaeroides 2.4.1(T) (99.9 % sequence similarity), Rba. megalophilus JA194(T) (99.8 %) and Rba. azotoformans KA25(T) (98.1 %) and clusters with other species of the genus Rhodobacter of the family Rhodobacteraceae. However, DNA-DNA hybridization with Rba. sphaeroides DSM 158(T), Rba. megalophilus JA194(T) and Rba. azotoformans JCM 9340(T) showed relatedness of only 38-57 % with respect to strain JA192(T). On the basis of 16S rRNA gene sequence analysis, DNA-DNA hybridization data and morphological, physiological and chemotaxonomic characters, strain JA192(T) represents a novel species of the genus Rhodobacter, for which the name Rhodobacter johrii sp. nov. is proposed. The type strain is JA192(T) (=DSM 18678(T) =JCM 14543(T) =MTCC 8172(T)).

Thiohalocapsa marina sp. nov., from an Indian marine aquaculture pond.

A spherical-shaped, phototrophic, purple sulfur bacterium was isolated in pure culture from anoxic sediment in a marine aquaculture pond near Bheemli (India). Strain JA142T is Gram-negative and non-motile. It has a requirement for NaCl (optimum of 2% and maximum of 6% w/v NaCl). Intracellular photosynthetic membranes are of the vesicular type. In vivo absorption spectra indicate the presence of bacteriochlorophyll a and carotenoids of the okenone series as photosynthetic pigments. Phylogenetic analysis on the basis of 16S rRNA gene sequences showed that strain JA142T is related to halophilic purple sulfur bacteria of the genera Thiohalocapsa and Halochromatium, with the highest sequence similarity to Thiohalocapsa halophila DSM 6210T (97.5%). Morphological and physiological characteristics differentiate strain JA142T from other species of the genera Halochromatium and Thiohalocapsa. Strain JA142T is sufficiently different from Thiohalocapsa halophila based on 16S rRNA gene sequence analysis and morphological and physiological characteristics to allow the proposal of a novel species, Thiohalocapsa marina sp. nov., with the type strain JA142T (=JCM 14780T=DSM 19078T).

Thiophaeococcus mangrovi gen. nov., sp. nov., a photosynthetic, marine gammaproteobacterium isolated from the Bhitarkanika mangrove forest of India.

A coccoid, phototrophic purple sulfur bacterium was isolated in pure culture from a mud sample collected from brackish water in the Bhitarkanika mangrove forest of Orissa, India, in a medium containing 2 % NaCl (w/v). This bacterium, strain JA304(T), was Gram-negative and had a requirement for NaCl. Intracellular photosynthetic membranes were of the vesicular type. The colour of the phototrophically grown culture was saddle-brown. Bacteriochlorophyll a and the carotenoid lycopene were present as photosynthetic pigments. Strain JA304(T) was able to grow photolithoautotrophically and could photoassimilate a number of organic substrates. Yeast extract was required for growth of strain JA304(T). The DNA G+C content was 68.1-68.9 mol%. 16S rRNA gene sequence comparisons indicate that the isolate represents a member of the Chromatiaceae within the class Gammaproteobacteria. According to sequence comparison data, strain JA304(T) is positioned distinctly outside the group formed by the four genera Thiocystis, Chromatium, Allochromatium and Thermochromatium, with only 86.7-91.0 % sequence similarity. Distinct morphological, physiological and genotypic differences from these previously described taxa support the classification of this isolate as a representative of a novel species in a new genus, for which the name Thiophaeococcus mangrovi gen. nov., sp. nov. is proposed. The type strain of Thiophaeococcus mangrovi is JA304(T) (=JCM 14889(T) =DSM 19863(T)).

[Comparative study of the fatty acid composition of some groups of purple nonsulfur bacteria].

The fatty acid composition (FAC) of 43 strains of purple nonsulfur bacteria belonging to six genera--Rubrivivax, Rhodopseudomonas, Rhodoplanes, Blastochloris, Rhodobium, and Rhodomicrobium--was studied by capillary gas chromatography. The cultures were grown on standard medium under standard conditions. Automatic identification of the fatty acid methyl esters and statistical processing of the results were performed by the computerized Microbial Identification System (M.I.S). Significant differences between the FACs of different genera, species, and, sometimes, strains were revealed. 16S rRNA genes of some of the new isolates, primarily those having a specific FAC, were sequenced. The taxonomic status of a number of the strains in question was determined using the FAC characteristics as one of the criteria. It was shown that the FAC characteristics may be used both for affiliating the isolates to known species and for revealing new taxa.

Two novel species of marine phototrophic Gammaproteobacteria: Thiorhodococcus bheemlicus sp. nov. and Thiorhodococcus kakinadensis sp. nov.

Two coccoid phototrophic purple sulfur bacteria were isolated from marine habitats (marine aquaculture pond near Bheemli, Visakhapatnam and marine tidal waters from a fishing harbour, Kakinada) in a medium that contained 3% NaCl (w/v). Strains JA132T and JA130T are Gram-negative, motile cocci with a single flagellum. Both have an obligate requirement for NaCl. Intracellular photosynthetic membranes are of the vesicular type. Bacteriochlorophyll a and most probably carotenoids of the spirilloxanthin series were present as photosynthetic pigments. Both strains were able to grow photolithoautotrophically and photolithoheterotrophically. Chemotrophic and fermentative growth could not be demonstrated. There is no vitamin requirement for strain JA132T, while strain JA130T requires niacin, biotin and pantothenate as growth factors. Phylogenetic analysis on the basis of 16S rRNA gene sequences showed that both strains cluster with species of the genus Thiorhodococcus belonging to the Gammaproteobacteria. The DNA G+C contents of strains JA132T and JA130T were 65.5 and 57.5 mol%, respectively. Based on the 16S rRNA gene sequence analysis, morphological and physiological characteristics, strains JA132T and JA130T are significantly different from each other and from other species of the genus Thiorhodococcus and are recognized as two novel species, for which the names Thiorhodococcus bheemlicus sp. nov. and Thiorhodococcus kakinadensis sp. nov. are proposed. The type strains of T. bheemlicus sp. nov. and T. kakinadensis sp. nov. are JA132T (=MTCC 8120T=ATCC BAA-1362T=JCM 14149T=DSM 18805T) and JA130T (=ATCC BAA-1353T=DSM 18858T=JCM 14150T), respectively.

Rhodobacter vinaykumarii sp. nov., a marine phototrophic alphaproteobacterium from tidal waters, and emended description of the genus Rhodobacter.

A rod-shaped, phototrophic, purple non-sulfur bacterium was isolated in pure culture from seawater collected from the seashore of Visakhapatnam, on the east coast of India, in a medium that contained 2 % NaCl (w/v). Strain JA123(T) was Gram-negative and non-motile and had a requirement for NaCl. Photo-organoheterotrophic and chemo-organoheterotrophic growth occurred with organic compounds as carbon sources and electron donors. Photolithoautotrophic, chemolithoautotrophic and fermentative growth could not be demonstrated. Strain JA123(T) contained vesicular intracellular photosynthetic membrane structures. Bacteriochlorophyll a and probably carotenoids of the spheroidene series were present as photosynthetic pigments. Biotin was required for growth. Phylogenetic analysis on the basis of 16S rRNA gene sequences showed that strain JA123(T) clustered with species of the genus Rhodobacter. Based on 16S rRNA gene sequence analysis and morphological and physiological characteristics, strain JA123(T) is sufficiently different from other Rhodobacter species to propose a novel species, Rhodobacter vinaykumarii sp. nov., to accommodate this strain; the type strain is JA123(T) (=DSM 18714(T) =JCM 14544(T) =CCUG 54311(T)).

Rhodovulum visakhapatnamense sp. nov.

A Gram-negative, rod-shaped, phototrophic bacterium (JA181(T)) was isolated from a tidal water sample. On the basis of 16S rRNA gene sequence similarity, strain JA181(T) was shown to belong to the class Alphaproteobacteria, most closely related to Rhodovulum sulfidophilum (97.8 % similarity to the type strain), Rhodovulum adriaticum (93 %), Rhodovulum robiginosum (93 %), Rhodovulum iodosum (94 %), Rhodovulum imhoffii (94 %), Rhodovulum strictum (95 %), Rhodovulum euryhalinum (94.6 %) and Rhodovulum marinum (94.6 %). DNA-DNA hybridization with Rdv. sulfidophilum DSM 1374(T) (relatedness of 39 % with strain JA181(T)) and physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain JA181(T) from the eight Rhodovulum species with validly published names. Strain JA181(T) therefore represents a novel species, for which the name Rhodovulum visakhapatnamense sp. nov. is proposed (type strain JA181(T) =JCM 13531(T) =ATCC BAA-1274(T) =DSM 17937(T)).

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.

Rhodobium gokarnense sp. nov., a novel phototrophic alphaproteobacterium from a saltern.

A pink-pigmented, phototrophic, purple nonsulfur bacterium, strain JA173(T), was isolated in pure culture from a saltern in Gokarna, India, in a medium containing 2 % (w/v) NaCl. Strain JA173(T) was a non-motile Gram-negative rod that multiplied by budding. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain JA173(T) clusters with the class Alphaproteobacteria; highest sequence similarity (98 %) was to the type strain of Rhodobium orientis and 94 % similarity was observed to the 16S rRNA gene sequence of the type strain of Rhodobium marinum. However, DNA-DNA hybridization with R. orientis DSM 11290(T) revealed a relatedness value of only 35.1 % with strain JA173(T). Strain JA173(T) contained lamellar internal membranes, bacteriochlorophyll a and carotenoids of the spirilloxanthin series. Strain JA173(T) had an obligate requirement for NaCl (optimum growth at 2-6 %, w/v) and grew photoheterotrophically with a number of organic compounds as carbon source or electron donor. Photoautotrophic, chemoautotrophic and fermentative growth could not be demonstrated. Yeast extract was required for growth. Based on 16S rRNA gene sequence analysis, DNA-DNA hybridization data and morphological and physiological characteristics, strain JA173(T) is sufficiently different from other species of the genus Rhodobium to be recognized as a representative of a novel species, Rhodobium gokarnense sp. nov. The type strain is JA173(T) (=ATCC BAA-1215(T)=DSM 17935(T)=JCM 13532(T)).

Rubrivivax benzoatilyticus sp. nov., an aromatic, hydrocarbon-degrading purple betaproteobacterium.

A brown-coloured bacterium was isolated from photoheterotrophic (benzoate) enrichments of flooded paddy soil from Andhra Pradesh, India. On the basis of 16S rRNA gene sequence analysis, strain JA2(T) was shown to belong to the class Betaproteobacteria, related to Rubrivivax gelatinosus (99 % sequence similarity). Cells of strain JA2(T) are Gram-negative, motile rods with monopolar single flagella. The strain contained bacteriochlorophyll a and most probably the carotenoids spirilloxanthin and sphaeroidene, but did not have internal membrane structures. Intact cells had absorption maxima at 378, 488, 520, 590, 802 and 884 nm. No growth factors were required. Strain JA2(T) grew on benzoate, 2-aminobenzoate (anthranilate), 4-aminobenzoate, 4-hydroxybenzoate, phthalate, phenylalanine, trans-cinnamate, benzamide, salicylate, cyclohexanone, cyclohexanol and cyclohexane-2-carboxylate as carbon sources and/or electron donors. The DNA G+C content was 74.9 mol%. Based on DNA-DNA hybridization studies, 16S rRNA gene sequence analysis and morphological and physiological characteristics, strain JA2(T) is different from representatives of other photosynthetic species of the Betaproteobacteria and was recognised as representing a novel species, for which the name Rubrivivax benzoatilyticus sp. nov. is proposed. The type strain is JA2(T) (=ATCC BAA-35(T)=JCM 13220(T)=MTCC 7087(T)).

Rhodovulum marinum sp. nov., a novel phototrophic purple non-sulfur alphaproteobacterium from marine tides of Visakhapatnam, India.

A yellowish-brown bacterium was isolated from enrichment cultures inoculated with seawater samples from the eastern coast of India (Visakhapatnam) under photoheterotrophic conditions. Enrichment and isolation in a medium containing 2 % NaCl (w/v) yielded strain JA128(T), which has ovoid to rod-shaped cells, also forms chains and is non-motile. Phylogenetic analysis on the basis of 16S rRNA gene sequences showed that strain JA128(T) clusters with the Alphaproteobacteria and the sequence similarity with its closest relatives, Rhodovulum iodosum and Rhodovulum sulfidophilum, was 95 %. Strain JA128(T) contained vesicular intracytoplasmic membranes, bacteriochlorophyll a and carotenoids of the spheroidene series. Strain JA128(T) was mesophilic, slightly acidophilic, slightly halophilic and grew photoheterotrophically with a number of organic compounds as carbon source and electron donor. It was unable to grow photoautotrophically, chemoautotrophically or by fermentative modes. It did not utilize sulfide, thiosulfate or hydrogen as electron donors. Thiamine was required as a growth factor. Based on the 16S rRNA gene sequence analysis, morphological and physiological characteristics, strain JA128(T) was significantly different from other species of the genus Rhodovulum and was recognized as a novel species for which the name Rhodovulum marinum sp. nov. is proposed. The type strain is JA128(T) (=ATCC BAA 1215(T)=CCUG 52183(T)=JCM 13300(T)).

Marichromatium indicum sp. nov., a novel purple sulfur gammaproteobacterium from mangrove soil 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 JA100(T) clusters with species of the genus Marichromatium of the class 'Gammaproteobacteria'. Cells of strain JA100(T) 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 JA100(T) 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 JA100(T) 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 JA100(T) (=DSM 15907(T)=ATCC BAA-741(T)=JCM 12653(T)).

Sponge-associated bacteria: general overview and special aspects of bacteria associated with Halichondria panicea.

Increasing evidence is accumulating that highlights the important role of bacteria in bacteria-sponge associations. It appears to be equally important to analyse the specific association of bacteria with sponges, to realise the biological function of biologically active substances produced by sponge-associated bacteria, and to consider the relationship between bacteria and sponges in the search for new pharmaceutical products. In this chapter the current knowledge on bacteria-sponge associations is briefly reviewed. Results are summarised that were obtained by three major methodological approaches: (1) classical microscope observations, (2) investigations attempting to characterise sponge-associated bacteria by describing pure culture isolates, and (3) the rapidly growing evidence from genetic analyses of sponge-associated bacteria. Special emphasis is given to the evidence of possible symbiotic interactions between bacteria and sponges and to the synthesis of natural products by bacteria isolated from or associated with marine sponges. Case studies including morphological and genetic studies together with results from pure culture studies have been performed with bacteria from the sponges Rhodopaloeides odorabile, Aplysina cavernicola, and Halichondria panicea. In addition, new results on bacteria associated with Halichondria panicea are also presented.

True marine and halophilic anoxygenic phototrophic bacteria.

Anoxygenic phototrophic bacteria are widely distributed in marine sediments and shallow waters of the coastal zone, where they often form intensely colored mass developments. The phototrophic bacteria have adapted to the whole spectrum of salt concentrations, from freshwater to saturated brines, and it is apparent that individual species have adapted well to particular habitats and mineral salts compositions, both qualitatively and quantitatively. This adaptation is reflected not only in the demand for defined ranges of salt concentrations, but also in the phylogenetic relationships of these bacteria, as established by 16S rDNA sequences. Major phylogenetic branches of purple sulfur bacteria are represented by: (1) marine and extremely halophilic Ectothiorhodospiraceae, (2) truly marine and halophilic Chromatiaceae and (3) freshwater Chromatiaceae, some of which are tolerant to low salt concentrations and are successful competitors in brackish and marine habitats. Quite similarly, salt-dependent green sulfur bacteria form distinct phylogenetic lines. In addition, also among the phototrophic alpha-Proteobacteria (purple nonsulfur bacteria), distinct phylogenetic lines of salt-dependent species are recognized. Available data give rise to the assumption that salt concentrations of natural habitats are an important selective factor that determines the development of a selected range of phototrophic bacteria in an exclusive way. As a consequence, the salt responses of these bacteria are reflected in their phylogenetic relationships.

Transfer of Pfennigia purpurea tindall 1999 (Amoebobacter purpureus Eichler and Pfennig 1988) to the genus Lamprocystis as Lamprocystis purpurea comb. nov.

On the basis of its close phylogenetic relationship to Lamprocystis roseopersicina, the phototrophic purple sulfur bacterium originally described as Amoebobacter purpureus and recently transferred to Pfennigia purpurea is reclassified as Lamprocystis purpurea comb. nov. In addition, an emended description of the genus Lamprocystis is given.

Transfer of Rhodopseudomonas acidophila to the new genus Rhodoblastus as Rhodoblastus acidophilus gen. nov., comb. nov.

Rhodopseudomonas acidophila has unique properties among the phototrophic alpha-Proteobacteria and is quite distinct from the type species of Rhodopseudomonas, Rhodopseudomonas palustris. Therefore, the transfer of Rhodopseudomonas acidophila to Rhodoblastus acidophilus gen. nov., comb. nov., is proposed. This proposal is in accordance with other taxonomic reclassifications proposed previously and fully reflects the phylogenetic distance from Rhodopseudomonas palustris.

Dihydroxylycopene diglucoside diesters: a novel class of carotenoids from the phototrophic purple sulfur bacteria Halorhodospira abdelmalekii and Halorhodospira halochloris.

The carotenoids in Halorhodospira abdelmalekii and Halorhodospira halochloris were analyzed by spectroscopic methods. The carotenoid composition of the two species was almost the same. Both species contained substantial amounts of unusual carotenoid glycoside fatty acid esters, which have been found for the first time in phototrophic purple bacteria. Methoxy-hydroxylycopene glucoside was a major component, and dihydroxylycopene diglucoside and dihydroxylycopene diglucoside diester were also found. Lycopene, rhodopin, and 3,4,3',4'-tetrahydrospirilloxanthin were present in very small amounts. Methoxy, glucosyl, and glucosyl ester groups were observed as substituents at the positions of the two original hydroxyl groups of dihydroxylycopene and made up approximately 20, 50, and 20%, respectively, of the total end groups (100%). The fatty acid components of the three carotenoid glucoside esters were the same (C12:0 and C14:1) and were rare in the cellular lipids of the two species.

Phylogeny and distribution of the soxB gene among thiosulfate-oxidizing bacteria.

A PCR protocol for the detection of sulfur-oxidizing bacteria based on soxB genes that are essential for thiosulfate oxidation by sulfur-oxidizing bacteria of various phylogenetic groups which use the 'Paracoccus sulfur oxidation' pathway was developed. Five degenerate primers were used to specifically amplify fragments of soxB genes from different sulfur-oxidizing bacteria previously shown to oxidize thiosulfate. The PCR yielded a soxB fragment of approximately 1000 bp from most of the bacteria. Amino acid and nucleotide sequences of soxB from reference strains as well as from new isolates and environmental DNA from a hydrothermal vent habitat in the North Fiji Basin were compared and used to infer relationships of soxB between sulfur-oxidizing bacteria belonging to various 16S rDNA-based phylogenetic groups. Major phylogenetic lines derived from 16S rDNA were confirmed by soxB phylogeny. Thiosulfate-oxidizing green sulfur bacteria formed a coherent group by their soxB sequences. Likewise, clearly separated branches demonstrated the distant relationship of representatives of alpha-, beta-, and gamma-Proteobacteria including representative species of the former genus Thiobacillus (now Halothiobacillus - gamma-Proteobacteria, Thiobacillus - beta-Proteobacteria and Starkeya - alpha-Proteobacteria). This general picture emerged although apparent evidence for lateral transfer of the soxB gene is indicated and comparison of soxB phylogeny and 16S rDNA phylogeny points to the significance of this gene transfer in hydrothermal vent bacterial communities of the North Fiji Basin.

Thioflavicoccus mobilis gen. nov., sp. nov., a novel purple sulfur bacterium with bacteriochlorophyll b.

A novel phototrophic purple sulfur bacterium was isolated from a flat, laminated microbial mat in a salt marsh near Woods Hole, Massachusetts, USA. The cells were monotrichously flagellated motile cocci with internal photosynthetic membranes of the tubular type. The main photosynthetic pigments were bacteriochlorophyll b and the carotenoid 3,4,3',4'-tetrahydrospirilloxanthin. The marine bacterium showed optimal growth in the presence of 2% salts. It was obligately phototrophic and strictly anaerobic. It grew photoautotrophically and photoassimilated acetate, pyruvate and ascorbate as the only organic substrates. In the presence of sulfide, elemental sulfur globules were formed inside the cells. Elemental sulfur was further oxidized to sulfate. The DNA base composition of the new bacterium was 66.5 mol% G+C. The 16S rDNA nucleotide sequence was most similar to strains of Thiococcus pfennigii, there being approximately 92-93% sequence similarity. The new bacterium is described as a new species and a new genus, and the name Thioflavicoccus mobilis is proposed; the type strain is 8321T (= ATCC 700959T).