Rheinheimera baltica gen. nov., sp. nov., a blue-coloured bacterium isolated from the central Baltic Sea.

A set of taxonomically unique, blue-coloured bacterial isolates are described on the basis of physiological and biochemical characterization, fatty acid profiling and analyses of 16S rDNA sequences. The flagellated, non-fermentative strains were isolated in 1986, 1987 and 1998 from different layers of the water column of the central Baltic Sea. According to 16S rDNA sequences, all strains are very closely related to each other and to strains from several other marine environments, including the deep sea. Thus, the described species seems to be widespread in marine habitats. According to DNA-DNA hybridization, the strains described can be considered to belong to the same species. The bacteria grew at temperatures from 4 to 30 degrees C, with an optimum around 20-25 degrees C. Growth was observed at salinities from 0 to 30, with an optimum between 10 and 30 and no growth at high salinities. The dominant fatty acids were 16:1omega7c, 16:0 and 18:1omega7c. The G+C content of the DNA ranged from 47.8 to 48.9 mol%. Phylogenetic analyses of the 16S rDNA sequences revealed a clear affiliation with members of the gamma-Proteobacteria. The closest relationship was seen with Alishewanella fetalis but, in terms of physiology, colour and fatty acids, the bacteria described are rather distant from A. fetalis. To honour the marine microbiologist Gerhard Rheinheimer, the name Rheinheimera baltica gen. nov., sp. nov., is suggested for the Baltic isolates, with the type strain OSBAC1T (= DSM 14885T = LMG 21511T).