Alkalibacterium iburiense sp nov., an obligate alkaliphile that reduces an indigo dye

Three indigo-reducing obligately alkaliphilic strains, M3(T), 41A and 41C, were isolated. The isolates grew at pH 9-12, but not at pH 7-8. They were Gram-positive, facultatively anaerobic, straight rod-shaped strains with peritrichous flagella. The isolates grew in 0-14% (w/v) NaCl, with optimum growth at 3-13%. They grew at temperatures between 10 and 45 degrees C, with optimum growth at around 30-37 degrees C. They did not hydrolyse starch or gelatin. DL-Lactate was the major end-product from D-glucose. No quinones could be detected. The peptidoglycan type was A4 beta, Orn-D-Asp. The major cellular fatty acids were C-16:0, C(16:1)7c and C(18:1)9c. The DNA G+C content was 42.6-43.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequence data indicated that the isolates belong to the genus Alkalibacterium. DNA-DNA hybridization revealed low similarity (less than 16%) of the isolates with respect to the two closest phylogenetically related strains, Alkalibacterium olivapovliticus and Alkalibacterium psychrotolerans. On the basis of phenotypic and chemotaxonomic characteristics, phylogenetic data and DNA-DNA relatedness, the isolates merit classification as a novel species of the genus Alkalibacterium, for which the name Alkalibacterium iburiense is proposed. The type strain is M3(T) (=JCM 12662(T)=NCIMB 14024(T)).