Rhodobaca bogoriensis gen. nov. and sp. nov., an alkaliphilic purple nonsulfur bacterium from African Rift Valley soda l
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O R I G I N A L PA P E R
Amy D. Milford · Laurie A. Achenbach · Deborah O. Jung · Michael T. Madigan
Rhodobaca bogoriensis gen. nov. and sp. nov., an alkaliphilic purple nonsulfur bacterium from African Rift Valley soda lakes Received: 18 January 2000 / Revised: 28 March 2000 / Accepted: 3 April 2000 / Published online: 17 May 2000 © Springer-Verlag 2000
Abstract From enrichment cultures established for purple nonsulfur bacteria using water and sediment samples from Lake Bogoria and Crater Lake, two soda lakes in the African Rift Valley, three strains of purple nonsulfur bacteria were isolated; strain LBB1 was studied in detail. Cells of strain LBB1 were motile and spherical to rod-shaped, suggesting a relationship to Rhodobacter or Rhodovulum species, and the organism was capable of both phototrophic and chemotrophic growth on a wide variety of organic compounds. Phototrophically grown cultures were yellow to yellow-brown in color and grew optimally at pH 9 (pH range 7.5–10) and 1% NaCl (range 0–10%). In physiological studies of strain LBB1, neither photoautotrophy (H2- or sulfide-dependent) nor nitrogen fixation was observed. Absorption spectra revealed that all three strains contained bacteriochlorophyll a and carotenoids of the spheroidene pathway and synthesized only a light-harvesting (LH) I-type photosynthetic antenna complex. Electron microscopy of cells of strain LBB1 revealed a vesicular intracytoplasmic membrane system, although only a few vesicles were observed per cell. The G+C content of strain LBB1 DNA was 59 mol%, significantly lower than that of known Rhodobacter and Rhodovulum species, and its phylogeny as determined by ribosomal RNA gene sequencing placed it within the Rhodobacter/Rhodovulum clade yet distinct from all described species of either of these genera. The unique assemblage of properties observed in strain LBB1 warrants its inclusion in a new genus of purple nonsulfur bacteria and the name Rhodobaca bogoriensis is proposed herein, the genus name reflecting morphological characteristics and the species epithet referring to the habitat.
A. D. Milford · L. A. Achenbach · D. O. Jung · M. T. Madigan (✉) Department of Microbiology and Center for Systematic Biology, Southern Illinois University, Carbondale, IL 62901-6508, USA e-mail: [email protected], Tel.: +1-618-4535130, Fax: +1-618-4535130
Key words Photosynthesis · Anoxygenic phototrophic bacteria · Purple nonsulfur bacteria · Extreme environments · Alkaliphily
Introduction Purple nonsulfur phototrophic bacteria are widely distributed in nature and reside with purple and green sulfur bacteria in sediments and lake waters (Imhoff 1992a; Madigan 1988). Most species of purple nonsulfur bacteria have been obtained from freshwater environments; however, Rhodovulum and Rhodobium species inhabit marine environments (Hiraishi and Ueda 1994; Hiraishi et al. 1995; Imhoff 1988). Anoxygenic phototrophic bacteria are also widespread in extreme environments including acidic (Pfennig 1969, 1974), alkaline (Imhoff and Trüper 1977, 1981; Imhoff e
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