NATRONOINCOLA HISTIDINOVORANS GEN. NOV., SP. NOV., A NEW ALKALIPHILICACETOGENIC ANAEROBE

Two strains, asporogenous Z-7940 and sporogenous Z-7939, of a moderate ly haloalkaliphilic, obligately anaerobic, fermentative bacteria, moti le, with Gram-positive cell wall structure, were isolated from soda de posits in Lake Magadi, Kenya. Both strains are mesophilic and utilize only two amino acids, histidine and glutamate, with formation of aceta te and ammonium as the main end products. Strain Z-7939 in addition is able to utilize pyruvate. DNA-DNA homology between strains Z-7940 and Z-7939 was 94%, indicating that in spite of phenotypic differences th ey belong to the same species. They are true alkaliphiles with a pH ra nge for growth of the type strain 2-7940 from pH 8.0 to pH 10.5, optim um at pH 9.4. Both strains obligately depend on sodium and bicarbonate ions. The optimum salt concentration for growth of the type strain is 8-10% wt/vol and the range from 4% to 16%. The G+C content of strain Z-7940 is 31.9 mol% and the strain Z-7939 is 32.3 mol%. Analysis of 16 S rDNA sequence of the type strain shows it to belong to cluster XI of the low G+C Gram-positive bacteria. On the basis of its distinct phyl ogenetic position and physiological properties, we propose a new genus and new species Natranoincola histidinovorans for these strains. The type strain is Z-7940 (=DSM 11416).