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A chemo-organotrophic iodide (I−)-oxidizing bacterial strain, C-3T, isolated from natural gas brine of an iodine recovery facility in Kujukuri, Chiba, Japan, was characterized for representation of a novel species in the class Alphaproteobacteria . Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the nearest neighbours of strain C-3T were members of the genera Eilatimonas , Kordiimonas , Rhodothalassium and Temperatibacter with 88–91 % sequence similarity. Cells of strain C-3T were aerobic, Gram-staining-negative, non-sporulating and rod-shaped (1.3–3.6 µm in length). Strain C-3T grew optimally at 30 °C, pH 7.5 and with 3 % NaCl (w/v). Iodide oxidation to form molecular iodine (I2) was a unique trait for strain C-3T, whereas the strain did not utilize iodide as a sole electron donor for chemolithoautotrophic growth. The major isoprenoid quinone was Q-10. The major cellular fatty acids were C18 : 1 ω7c and C16 : 1 ω5c. The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and unidentified aminolipids. The G+C content of the genomic DNA was 58.5 mol%. Iodide oxidation and the major cellular fatty acids composition distinguished strain C-3T from phylogenetically related bacteria. On the basis of the phenotypic features and the phylogenetic position, a novel genus and species are proposed for strain C-3T (=JCM 17843T=LMG 28660T), to be named Iodidimonas muriae gen. nov., sp. nov. We also propose to place the distinct sublineages of the genera Iodidimonas gen. nov. and Emcibacter in the orders Iodidimonadales ord. nov. and Emcibacterales ord. nov., respectively, because these genera are located far apart from the order Kordiimonadales and form the distinct lineage in the class Alphaproteobacteria .

Rho' do.tha.las' si.um. Gr. n. rhodon the rose; Gr. adj. thalassios belonging to the sea; M.L. neut. n. Rhodothalassium the rose belonging to the sea. Proteobacteria / Alphaproteobacteria / Rhodobacterales / Rhodobacteraceae / incertae Sedis XXVI. Rhodothalassium Cells are vibrioid to spiral-shaped, motile by means of polar flagella and multiply by binary fission. Gram-negative members of the Alphaproteobacteria. Internal photosynthetic membranes are present as lamellar stacks lying parallel to the cytoplasmic membrane. Photosynthetic pigments are bacteriochlorophyll a (esterified with phytol) and carotenoids of the spirilloxanthin series. Ubiquinones and menaquinones with 10 isoprene units (Q-10 and MK-10) are present. Major cellular fatty acids are C18:1, C18:0, and C16:0, with C18:1 as dominant component (~60% of total fatty acids). Cells grow preferably photoheterotrophically under anoxic conditions in the light. Chemotrophic growth is possible under oxic conditions in the dark. Amino acids may be required as growth factors. Obligately halophilic bacteria that require NaCl or sea salt for growth, have salt optima above seawater salinity and an extended salt tolerance. Habitat: anoxic zones of hypersaline environments such as salterns and salt lakes that are exposed to the light. The mol% G + C of the DNA is: 64.0. Type species: Rhodothalassium salexigens (Drews 1982) Imhoff, Petri and Suling 1998, 797 (Rhodospirillum salexigens Drews 1982, 384.) Keywords: Rhodothalassium; Rhodothalassium salexigens; Rhodobacteraceae fam. nov.

The family Rhodobacteraceae can be considered a paradigm of modern taxonomy of prokaryotes. Taking into account the number of species and genera that conforms the family, together with the knowledge about their abundance and vast global distribution, it surprises that most of them have been described relatively recent to our days. Two notable exceptions are Rhodonostoc capsulatum (Molisch, Die purpurbakterien nach neuen untersuchungen, vols i–vii. G. Fischer, Jena, pp 1–95, 1907) and Micrococcus denitrificans Beijerinck and Minkman (Zentbl Bakteriol, Parasitenkd, Infektionskr Hyg. Abt II 25:30–63, 1910), early basonyms of Rhodobacter capsulatus and Paracoccus denitrificans, respectively. The fact that so many descriptions within this family are recent means that some studies have been concomitant and pose a challenge not only for pure taxonomic studies but also for interpreting other studies in which a rapidly evolving nomenclature had to be used anyway. The metabolic and ecological diversity of the group adds further complexity. In spite of all these difficulties, the picture is far from being a chaos and it can be considered an exciting and important bacterial group to study. Rhodobacteraceae are, fundamentally, aquatic bacteria that frequently thrive in marine environments. They comprise mainly aerobic photo- and chemoheterotrophs but also purple non-sulfur bacteria which perform photosynthesis in anaerobic environments. They are deeply involved in sulfur and carbon biogeochemical cycling and symbiosis with aquatic micro- and macroorganisms. One hundred genera are currently recognized as members of the family although the Stappia group, Ahrensia, Agaricicola, and Rhodothalassium do not belong, phylogenetically, to the family. The 90 other genera are distributed in 5 phylogenetic groups (the Rhodobacter, the Paracoccus, the Rhodovulum, the Amaricoccus, and the Roseobacter clades) that might be considered a family on its own.

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.

Udgivelsesdato: 6 December 2007 A Gram-negative, strictly aerobic, diplococcoid bacterium (strain D2-3T) was isolated from the biofilter of a recirculating marine aquaculture system. Phylogenetic analysis of the 16S rRNA gene sequence of D2-3T indicated that the new organism occupied a novel lineage within the α-1 subclass of Proteobacteria and was related to the genera Rhodothalassium, Azospirillum, Craurococcus, Acidiphilium, and Tistrella. The highest sequence similarity (90.8%) of the 16S rRNA gene sequence of D2-3T was to that of Candidatus “Alysiosphaera europaea”. D2-3T was mesophilic, heterotrophic, required sea salt, and had a pH optimum of 8.0. Growth in the presence of light resulted in the formation of pink colonies, a 25% increased cell yield, and a slightly increased growth rate. D2-3T contained carotenoids and low amounts of bacteriochlorophyll a. Membranes of D2-3T contained b-type cytochromes. The G+C content of the DNA was 60.3±0.1 mol%. Phylogenetic, morphological, physiological, and biochemical analyses demonstrated that D2-3T represented a new aerobic phototrophic genus, for which the name Geminicoccus roseus gen. nov., sp. nov. is proposed for the type species (D2-3T=DSM 18922T=ATCC BAA-1445T).

The 165 rDNA sequence of Rhodospirillum mediosalinum was determined and compared with corresponding sequences from other spiral-shaped purple non-sulfur bacteria classified as or related to the genus Rhodospirillum in the alpha subclass of the Proteobacteria. Sequence similarities separate the currently recognized Rhodospirillum species into five different groups with no more than 91% sequence similarity, clearly indicating the necessity to recognize these groups as different genera. Major diagnostic properties of these bacteria are compared and new genera Phaeospirillum gen. nov., Roseospira gen. nov., Rhodothalassium gen. nov. and Rhodovibrio gen. nov. are described with the species Phaeospirillum fulvum comb. nov., Phaeospirillum molischianum comb. nov., Rhodovibrio salinarum comb. nov., Rhodovibrio sodomensis comb. nov., Rhodothalassium salexigens comb. nov. and Roseospira mediosalina comb. nov. The genus Rhodospirillum is represented by Rhodospirillum rubrum and Rhodospirillum photometricum and an emended description of this genus is also given.