Summary auto-generated
This study describes Rheinheimera baltica, a new genus and species of blue-colored marine bacteria isolated from the Baltic Sea. Eleven strains were collected from different depths and time periods (1986-1998) at two locations in the central Baltic Sea. The bacteria are Gram-negative, flagellated rods or cocci that grow aerobically at 4-30°C with optimal growth at 20-25°C. They tolerate salinities from 0-3% without high-salinity tolerance. Phylogenetic analysis of 16S rRNA gene sequences revealed the strains belong to γ-Proteobacteria, most closely related to Alishewanella fetalis but physiologically distinct. Key phenotypic differences include flagella presence, lower temperature optimum, lack of anaerobic respiration capability, and different fatty acid composition. DNA-DNA hybridization showed high similarity (87-99%) among strains collected years apart and kilometers apart, confirming they represent a single species. The dominant fatty acids were 16:1ω7c, 16:0, and 18:1ω7c, with DNA G+C content of 47.8-48.9 mol%. The genus was named in honor of marine microbiologist Gerhard Rheinheimer. Strain OSBAC1T is designated as the type strain.
Key findings
- Rheinheimera baltica is a new genus and species of blue-colored, flagellated, aerobic marine bacteria from the Baltic Sea belonging to γ-Proteobacteria
- Strains grow optimally at 20-25°C with low-salinity preference (0-3% NaCl) and lack anaerobic respiration capability, distinguishing them from their closest phylogenetic relative Alishewanella fetalis
- DNA-DNA hybridization (87-99% similarity) and 16S rRNA sequences (98.7-100% similarity) confirm all 11 isolates collected over 12 years from different locations belong to a single species
- The bacteria are widespread in marine environments, with related sequences found in deep-sea environments and dinoflagellate cultures, indicating global distribution
- Dominant cellular fatty acids are 16:1ω7c (34.8%), 16:0 (22.1%), and 18:1ω7c (15.2%), with DNA G+C content of 47.8-48.9 mol%
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Abstract
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 comparison of the 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 OSBAC1(T) (=DSM 14885(T)=LMG 21511(T)).