Spirochaeta dissipitropha sp. nov., a New Alkaliphilic, Obligately Anaerobic Bacterium Isolated from Owens Lake in California and Emended Description of the Genus Spirochaeta

Abstract:  A novel obligately anaerobic, mesophilic, alkaliphilic spirochete, strain ASpC2, was isolated from an anaerobic sediment of the alkaline, hypersaline Owens Lake, USA. The Gram-negative cells are motile with helical shape and sizes of 0.23 x 8.0-18.0 micrometers. Growth was observed over the following ranges: temperature 10 C to 43 C; optimum 37 C; NaCl concentration 1-3 % (w/v); optimum NaCl 2 % (w/v) and pH 8- 10.5; optimum pH 10.0. The novel isolate is strictly alkaliphilic and requires high concentrations of carbonate-ions in the medium. New isolate utilizes some sugars, organic acids, amino acids, yeast extract, and peptone. The main end products of glucose fermentation are: CO2, acetate, ethanol, and formate. Strain ASpC2 is resistant to kanamycin, and rifampin, but sensitive to ampicillin, chloramphenicol, gentamycin and tetracycline. The GC content in DNA of the new isolate is 43.8 mol%, genome size is 6xl0(exp 8) Daltons, Tm of genomic DNA is 71 plus or minus 0.03 C. DNA-DNA hybridization exhibited 46% homology with the phylogeneticaily closest species, Spirochaeta asiatica strain Z-7491. On the basis of physiological and molecular properties, the taxonomic position for new isolate occurs on the level of a separate new species within the Spirochaeta genus. The name Spirochaeta dissipitropha sp. nov., is suggested for the new isolate (type strain ASpC2= ATCC BAA-1083= JCM 12856). Since this new species is able to utilize some amino acids and proteolysis products an emended diagnosis for the genus Spirochaeta is proposed.