Spirochaeta dissipatitropha sp. nov., an alkaliphilic, obligately anaerobic bacterium, and emended description of the genus Spirochaeta Ehrenberg 1835

Abstract

A novel obligately anaerobic, mesophilic, alkaliphilic spirochaete, strain ASpC2 T , was isolated from an anaerobic sediment of alkaline, hypersaline Owens Lake in California, USA. The Gramnegative cells are motile, helical in shape and 0.23¾8.0-18.0 mm. Growth occurs within the following ranges: 13-41 6C, with optimal growth at 35 6C; 1-3 % (w/v) NaCl, with optimal growth at 2 % (w/v) NaCl; and pH 7.8-10.5, with optimal growth at pH 10.0. The novel isolate is strictly alkaliphilic and requires high concentrations of carbonate ions in the medium. It utilizes some sugars, some organic acids, some amino acids, Casamino acids, yeast extract and peptone. The main end products of glucose fermentation are CO 2 and acetate. Strain ASpC2 T is resistant to kanamycin and rifampicin, but sensitive to ampicillin, chloramphenicol, gentamicin and tetracycline. The DNA G+C content of the new isolate is 43.8 mol%, its genome size is 6¾10 8 Da and the melting temperature of its genomic DNA is 71 6C. DNA-DNA hybridization experiments demonstrated 46 % similarity with the phylogenetically most closely related species, Spirochaeta asiatica Z-7591 T . On the basis of physiological and molecular properties, the new isolate belongs taxonomically to a novel species within the genus Spirochaeta, for which the name Spirochaeta dissipatitropha sp. nov. is proposed (type strain, ASpC2 T 5ATCC BAA-1083 T 5JCM 12856 T ). S. dissipatitropha ASpC2 T is the second strain in the genus (after Spirochaeta smaragdinae SEBR 4228 T ) that is able to use proteolysis products as the sole energy source, and additional tests have shown that other halo-alkaliphilic spirochaetes (Spirochaeta americana, Spirochaeta alkalica and Spirochaeta africana) are also able to grow on yeast extract alone; therefore, an emended description for the genus Spirochaeta is given.

Biased gene transfer and its implications for the concept of lineage

“…This genus represents a group of saccharolytic, facultatively anaerobic or obligately anaerobic free-living spirochetes that thrive in a variety of aquatic environments. A number of species inhabit extreme environments, including S. halophila isolated from a high-salinity pond on the Sinai shore [19], S. thermophila from brackish and marine hot springs in New Zealand and Russia [20], S. caldaria from freshwater [21], S. smaragdinae from an African oil field [22], S. americana from alkaline, hypersaline Mono Lake [23], and S. dissipatitropha from anaerobic sediments of the alkaline, hypersaline Owens Lake in California [24]. Based on 16S rRNA relationships, Spirochaeta shows closest affinities with the host-associated genera Treponema and Borrelia [18].…”

Complete genome sequence of the halophilic bacterium Spirochaeta africana type strain (Z-7692T) from the alkaline Lake Magadi in the East African Rift

“…Major components detected in the fatty acid analysis are the fatty acids C 14:0 (6.6%), C 16:1cis9 (6.3%), C 16:0 (19.0%), C 18:1cis-9 (1.4%), summed feature 10 (C 18:1cis11/trans9/trans6 and/or an unknown fatty acid with an equivalent chain length of 17.834) (34.9%), C 18:0 (1.8%), C 20:1cis13/trans11 (2.4%), as well as dimethyl acetals (DMA)/aldehydes (ALDE) probably derived from plasmalogens, C 14:0 DMA (5.0%), C 16:0 ALDE (3.8%), C 16:1cis-9 DMA (1.1%), C 16:0 DMA (15.3%), C 18:1cis11 DMA (0.8%) [35]. No data are available on polar lipid, quinone or other cell wall/envelope components that may be taxonomically significant…”

Cryoprotection from bacterial teichoic acid

“…4,31,48 Even though the bacteria may be quiescent, this could have an important role of cryosurvival, in particular extremophiles found in ice-core samples. [21][22][23][24][25][26][27][28][29][30][49][50][51] …”

“…20 Microbes survive in frozen ecosystems. 4,5,[9][10][11][12][13][21][22][23][24][25][26][27][28] The search for extraterrestrial life is directed towards the polar ice caps of Mars. 29,30 These phenomena will benefit by defining the conditions under which life can exist.…”