Abstract
A motile, Gram-positive, boron-tolerant and moderately halotolerant rod-shaped bacterium was isolated from a soil naturally high in boron minerals found in the Hisarcik area of Turkey. The novel isolate, designated T-16XT, produced spherical or ellipsoidal endospores in a non-bulging or slightly swollen sporangium in a terminal position and survived in a medium containing up to 450 mM boron. Whereas it tolerated 11 % (w/v) NaCl, it also grew without NaCl or boron. The temperature range for growth was 1637 °C (optimum 2528 °C) and the pH range for growth was 6.010.0 (optimum pH 7.58.5). The DNA G+C content was 35.8 mol% and the major cellular fatty acids were iso-C15 : 0 and anteiso-C15 : 0 at 18.2 and 45.7 % of the total fatty acids, respectively. MK-7 (90 %) was the predominant respiratory quinone system and meso-diaminopimelic acid was the predominant diamino acid of the cell-wall peptidoglycan. Phylogenetic analysis of the 16S rRNA gene sequence revealed that the novel strain is closely related to the type strains of Gracilibacillus orientalis (96.7 % similarity), G. halotolerans (95.5 %) and G. dipsosauri (95.4 %). However, the maximum DNA hybridization value for this strain with these closely related strains was less than 26.2 %. On the basis of 16S rRNA gene sequence data and chemotaxonomic and physiological features, the organism T-16XT (=DSM 17256T=IAM 15263T=ATCC BAA-1190T) is proposed to be a member of the genus Gracilibacillus as the type strain of the novel species Gracilibacillus boraciitolerans sp. nov.