ISOLATION AND CHARACTERIZATION OF A NOVEL ALKALITOLERANT THERMOPHILE,ANAEROBRANCA-HORIKOSHII GEN-NOV, SP-NOV

Nine moderately alkalitolerant thermophilic bacteria with similar prop erties were isolated from water and soil samples obtained from Yellows tone National Park. These Gram-type-positive, rod-shaped bacteria prod uce cells with primary branches. The cells are peritrichous and exhibi t only slight tumbling motility. At 60 degrees C the pH range for grow th is 6.9 to 10.3, and the optimum pH is 8.5. At pH 8.5 the temperatur e range for growth is 34 to 66 degrees C, with an optimum temperature of 57 degrees C, The strains are mainly proteolytic. The fermentation products from yeast extract are acetate, CO2, and H-2. Fumarate added to minimal medium containing yeast extract is stoichiometrically conve rted to succinate, indicating that it is used as an alternative electr on acceptor, The DNA G+C content is 33 to 34 mol%, On the basis of its unique properties, such as branch formation, growth at alkaline pH va lues at elevated temperatures, and the relative distance of its 16S rR NA sequence from those of other known bacteria, we propose that strain JW/YL-138(T) (T = type strain) and eight similar strains represent a new genus and species, Anaerobranca horikoshii, Strain JW/YL-138 is de signated the type strain of the type species, A, horikoshii, which was named in honor of Koki Horikoshi, a pioneer in the field of alkaliphi lic bacteria.