Rhodospirillum sodomense,sp. nov., a Dead Sea rhodospirillum species |
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Authors: | E. Erin Mack Linda Mandelco Carl R. Woese Michael T. Madigan |
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Affiliation: | (1) Department of Microbiology, Southern Illinois University, 62901 Carbondale, IL, USA;(2) Department of Microbiology, University of Illinois, 61801 Urbana, IL, USA;(3) Present address: Department of Microbiology, University of California, 95616 Davis, CA, USA |
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Abstract: | A new species of halophilic anoxygenic purple bacteria of the genus Rhodospirillum is described. The new organism, isolated from water/sediment of the Dead Sea, was vibrio-shaped and an obligate halophile. Growth was best at 12% NaCl, with only weak growth occurring at 6% or 21% NaCl. Growth occurred at Mg2+ concentrations up to 1 M but optimal growth was obtained at 0.05–0.1 M Mg2+. Bromide was well tolerated as an alternative anion to chloride. The new organism is an obligate phototroph, growing photoheterotrophically in media containing yeast extract and acetate or a few other organic compounds. Growth of the Dead Sea Rhodospirillum species under optimal culture conditions was slow (minimum td 20 h). Cells contained bacteriochlorophyll a and carotenoids of the spirilloxanthin series and mass cultures were pink in color. Absorption spectra revealed the presence of a B875 (light-harvesting I) but no B800/B850 (light-harvesting II) photopigment complex. The new organism shares a number of properties with the previously described halophilic phototrophic bacterium Rhodospirillum salinarum and was shown to be related to this phototroph by 16S rRNA sequencing. However, because of its salinity requirements, photosynthetic properties, and isolation from the Dead Sea, the new phototroph is proposed as a new species of the genus Rhodospirillum, R. sodomense. |
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Keywords: | Anoxygenic phototrophic bacteria Purple bacteria Rhodospirillum sodomense Dead Sea Hypersaline environments Photosynthesis |
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