Phaeovibrio sulfidiphilus gen. nov., sp. nov., phototrophic alphaproteobacteria isolated from brackish water

Two strains (JA317 T and JA559) of spiral shaped, spheroplast-forming, anaerobic,Gram-negative, motile purple non-sulfur bacteria were isolated from rhizosphere soils of paddy and were characterized by a polyphasic taxonomic approach. Bacteriochlorophyll a and carotenoids, rhodopin, lycopene and rhodopin glucoside, were present as photosynthetic pigments. Intracellular photosynthetic membranes were of stacked type. The major fatty acids were C 18 : 1 v7c, C 16 : 0 and C 16 : 1 v6c/C 16 : 1 v7c in both strains. The genomic DNA G+C content was 63.3±0.8 mol%. The two strains were closely related (mean DNA-DNA hybridization .85 %). Phylogenetic analysis showed that the strains clustered with the species of the genus Phaeospirillum, which belongs to the family Rhodospirillaceae within the class Alphaproteobacteria. Based on 16S rRNA gene sequence analysis, strains JA317 T and JA559showed highest sequence similarity with the type strains of Phaeospirillum chandramohanii (98.2 %), Phaeospirillum molischianum (97.4 %) and Phaeospirillum fulvum (97.1 %) of the family Rhodospirillaceae. Strain JA317 T can be clearly distinguished from P. chandramohanii with respect to spheroplast formation and several other morphological and physiological properties. DNA-DNA relatedness of strain JA317 T with its closest relatives of the genus Phaeospirillum was less than 55 %. It is evident from the phenotypic, chemotaxonomic and molecular genetic evidence that strain JA317 T represents a novel species of the genus Phaeospirillum, for which the name Phaeospirillum oryzae sp. nov., is proposed. The type strain of the species is JA317

Rhodoplanes pokkaliisoli sp. nov., a phototrophic alphaproteobacterium isolated from a waterlogged brackish paddy soil T ).Pokkali is a unique variety of rice that is cultivated organically in waterlogged brackish regions of Ernakulam, Kerala, India. This variety of rice, which gets no fertilizer or manure, draws nutrients from prawn excrement and other remnants. During our studies on the distribution of purple bacteria from paddy soils of India, strain JA415 T was isolated from the pokkali fields. Based on 16S rRNA gene sequencing analysis, strain JA415 T belonged to the genus Rhodoplanes, family Hyphomicrobiaceae, class Alphaproteobacteria. At the time of writing, the genus Rhodoplanes comprised three species with validly published names: Rhodoplanes roseus, Rhodoplanes elegans (Hiraishi & Ueda, 1994) and Rhodoplanes serenus (Okamura et al., 2009). The name of a further species, 'Rhodoplanes cryptolactis' (Okamura et al., 2007), has not been validly published. The type strains of these species were isolated from activated sludge from a sewage-treatment plant (Rpl. elegans) and sediment (Rpl. roseus) and water (Rpl. serenus) from freshwater ponds. The type strain of 'Rpl. cryptolactis' was isolated from a hot spring.

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The genus Rhodospirillum is represented by four species, with three of them showing phylogenetic divergence compared to the type species, Rhodospirillum rubrum . Differences in the major diagnostic properties such as internal photosynthetic membranes, quinones, fatty acids, carotenoid composition and a few other phenotypic properties warrant the reclassification of members of this genus. Resultantly, a new genus, Pararhodospirillum gen. nov., is proposed based on the analysis of nine strains to accommodate Rhodospirillum photometricum , Rhodospirillum sulfurexigens and Rhodospirillum oryzae as Pararhodospirillum photometricum comb. nov., Pararhodospirillum sulfurexigens comb. nov. and Pararhodospirillum oryzae comb. nov., respectively. The type species of the genus is Pararhodospirillum photometricum comb. nov. An emended description of the genus Rhodospirillum is also proposed.