Thiocapsa imhoffii , sp. nov., an alkaliphilic purple sulfur bacterium of the family Chromatiaceae from Soap Lake, Washi
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ORIGINAL PAPER
Thiocapsa imhoffii, sp. nov., an alkaliphilic purple sulfur bacterium of the family Chromatiaceae from Soap Lake, Washington (USA) Marie Asao Æ Shinichi Takaichi Æ Michael T. Madigan
Received: 21 March 2007 / Revised: 5 July 2007 / Accepted: 11 July 2007 / Published online: 28 July 2007 Springer-Verlag 2007
Abstract An alkaliphilic purple sulfur bacterium, strain SC5, was isolated from Soap Lake, a soda lake located in east central Washington state (USA). Cells of strain SC5 were gram-negative, non-motile, and non-gas vesiculate cocci, often observed in pairs or tetrads. In the presence of sulfide, elemental sulfur was deposited internally. Liquid cultures were pink to rose red in color. Cells contained bacteriochlorophyll a and spirilloxanthin as major photosynthetic pigments. Internal photosynthetic membranes were of the vesicular type. Optimal growth of strain SC5 occurred in the absence of NaCl (range 0–4%), pH 8.5 (range pH 7.5–9.5), and 32C. Photoheterotrophic growth occurred in the presence of sulfide or thiosulfate with only a limited number of organic carbon sources. Growth factors were not required, and cells could fix N2. Dark, microaerobic growth occurred in the presence of both an organic carbon source and thiosulfate. Sulfide and thiosulfate served as electron donors for photoautotrophy, which required elevated levels of CO2. Phylogenetic analysis placed strain SC5 basal to the clade of the genus Thiocapsa in the family Chromatiaceae with a 96.7% sequence similarity to its closest relative, Thiocapsa roseopersicina strain 1711T (DSM217T). The unique assemblage of physiological and phylogenetic properties of strain SC5
Communicated by Erko Stackebrandt. M. Asao M. T. Madigan (&) Department of Microbiology, Southern Illinois University, Carbondale, IL 62901-6508, USA e-mail: [email protected] S. Takaichi Biological Laboratory, Nippon Medical School, 297 Kosugi-cho 2, Nakahara, Kawasaki 211-0063, Japan
defines it as a new species of the genus Thiocapsa, and we describe strain SC5 herein as Tca. imhoffii, sp. nov. Keywords Anoxygenic phototrophic bacteria Purple sulfur bacteria Chromatiaceae Thiocapsa Alkaliphiles Extreme environments Soap Lake Soda lakes Abbreviations Tca Thiocapsa Tac Thioalkalicoccus Tco Thiococcus Chr Chromatium Alc Allochromatium
Introduction Anoxygenic phototrophic purple sulfur bacteria are grouped into two families, the Chromatiaceae and the Ectothiorhodospiraceae. These two families form phylogenetically distinct clades within the Gammaproteobacteria (Imhoff 1995, 2005). Anoxygenic phototrophic bacteria have been isolated from various extreme environments. These include in particular alkaliphilic phototrophs, with species of Ectothiorhodospiraceae comprising a majority of the alkaliphilic anoxygenic phototrophs characterized (Imhoff and Su¨ling 1996; Bryantseva et al. 1999a; Madigan 2003). In contrast, alkaliphilic species of Chromatiaceae are represented at present by a single species, Thioalkalicoccus limnaeus (Bryantseva et al. 2000; M
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