Rhodobaca bogoriensis gen. nov. and sp. nov., an alkaliphilic purple nonsulfur bacterium from African Rift Valley soda lakes

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.

Depth Distribution of Microbial Diversity in Mono Lake, a Meromictic Soda Lake in California

“…2A and 3) and were found in libraries generated from the 2-, 17.5-, and 23-m samples. The nearly full-length sequence (1,391 bp) of one of these clones (ML602J-43) was 97 to 98% similar to Rhodobaca bogoriensis (46), Roseonatronobacter thiooxidans (64), and Natronohydrobacter thiooxidans. It was also 97% similar to a bacterium (ML-168a) previously isolated from Mono Lake sediment (GenBank description).…”

“…R. bogoriensis is an anoxygenic, phototrophic, alkaliphilic purple nonsulfur bacterium isolated from soda lakes in the African Rift Valley (GenBank description). It is capable of both phototrophic growth and chemoautotrophic growth on a wide variety of organic compounds (46). R. thiooxidans is a strictly aerobic and obligately heterotrophic alkaliphile isolated from Russian soda lakes (64).…”

Planktonic bacterial community composition of an extremely shallow soda pond during a phytoplankton bloom revealed by cultivation and molecular cloning

“…Among the Böddi-szék isolates, those capable of photosynthesis showed 95-95 % sequence similarities to the halophilic species of Erythrobacter longus (Csotonyi et al 2008) and to the alkaliphilic species of Rhodobaca bogoriensis (Milford et al 2000). These purple non-sulfur bacteria are mixotrophs which use dissolved organic matter under aerobic conditions but are able to use the light and inorganic nutrients for their anoxic photosynthesis as well.…”

“…Besides the oxygen-producing cyanobacteria, the dominant presence of sulfide in the water and the anoxic circumstances can provide favorable conditions for mass production of haloalkaliphilic phototrophic purple sulfur and non-sulfur bacteria, which may play a role in the development of the reddish-brown discoloration of these lakes (Jones et al 1998;Mesbah et al 2007;Milford et al 2000;Mwirichia et al 2011). …”

Structure of the dimeric RC–LH1–PufX complex from Rhodobaca bogoriensis investigated by electron microscopy

“…The latter fraction was carefully collected using a syringe and applied to a Mono Q anion exchange fast protein liquid chromatography column (GE Healthcare) preequilibrated with 50 mm Tris-HCl (pH 8) and 0.015 per cent n-b-dodecyl maltoside. After washing with 5 ml of buffer, the complexes were eluted with a 30 ml linear gradient of 0-500 mM NaCl at a rate of 0.5 ml min 21 . The dimer fraction was collected and concentrated by gel filtration (Superose-6 column, GE Healthcare).…”