SPIROCHAETA-ALKALICA SP-NOV, SPIROCHAETA-AFRICANA SP-NOV, AND SPIROCHAETA-ASIATICA SP-NOV, ALKALIPHILIC ANAEROBES FROM THE CONTINENTAL SODALAKES 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 h alophilic S. africana sp. nov. Z-7692 (DSM 8902) from the soda-deposit ing Lake Magadi in Central Africa and haloalkaliphilic S. asiatica sp. nov. Z-7591 (DSM 8901) from Lake Khatyn, Central Asia. These mesophil ic spirochetes develop at pHs of >9 as anaerobic saccharolytic dissipo trophs. The DNA base compositions (moles percent G+C) of the strains w ere as follows: S. alkalica Z-7491, 57.1; S. africana Z-7692, 56.1; an d 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 ferme ntation were acetate, hydrogen, ethanol, and lactate, in different pro portions, for S. alkalica and S. africana; for S. asiatica, they were acetate, ethanol, and lactate. S. asiatica is strictly anaerobic, whil e S. alkalica and S. africana are rather aero-tolerant. All three spec ies group within the radiation of the majority of the species of the g enus Spirochaeta. Studies of the genes encoding 16S rRNA indicate a po ssible fanning out of the phylogenetic tree of spirochetes.