Spirochaeta alkalica sp nov, Spirochaeta africana sp nov, and Spirochaeta asiatica sp nov, alkaliphilic anaerobes from the Continental soda lakes in Central Asia and the East African Rift

During a study of microbial communities in athalassic bodies of water, three new species within the genus Spirochaeta were described. These are alkaliphilic Spirochaeta alkalica sp. nov. Z-7491 (DSM 8900) and halophilic S. africana sp. nov. Z-7692 (DSM 8902) from the soda-depositing Lake Magadi in Central Africa and haloalkaliphilic S. asiatica sp. nov. Z-7591 (DSM 8901) from Lake Khatyn, Central Asia. These mesophilic spirochetes develop at pHs of >9 as anaerobic saccharolytic dissipotrophs. The DNA base compositions (moles percent G+C) of the strains were as follows: S. alkalica Z-7491, 57.1; S. africana Z-7692, 56.1; and S. asiatica Z-7591, 49.2. The optimum growth parameters (temperature, pH, and NaCl concentration [percent, wt/vol], respectively) were as follows: for S. alkalica Z-7491, 35 degrees C, 9.2, and 5 to 7%; for S. africana Z-7692, 35 degrees C, 9.3, and 5 to 7%; and for S. asiatica Z-7591, 35 degrees C, 8.9, and 3 to 6%: The products of glucose fermentation were acetate, hydrogen, ethanol, and lactate, in different proportions, for S. alkalica and S. africana; for S. asiatica, they were acetate, ethanol, and lactate. S. asiatica is strictly anaerobic, while S. alkalica and S. africana are rather aero-tolerant. All three species group within the radiation of the majority of the species of the genus Spirochaeta. Studies of the genes encoding 16S rRNA indicate a possible fanning out of the phylogenetic tree of spirochetes.