Photobacterium halotolerans sp nov., isolated from Lake Martel in Spain

A halotolerant bacterium was isolated from a saline lake located in Mallorca, Spain. Cells of the strain, designated MACL01(T), were Gram-negative, rod-shaped and motile by means of polar flagella. Colonies of strain MACL01(T) were white to cream in TSA medium, turning brown after 7 days of incubation; they were blue in thiosulphate/citrate/bile salts/sucrose agar medium. A neighbour-joining phylogenetic analysis based on 16S rRNA gene sequences showed that strain MACL01(T) belongs to the genus Photobacterium, in which it forms a distinct lineage together with Photobacterium rosenbergii and Photobacterium, ganghwense (showing 96.9 and 96.2 % similarity, respectively). The most closely related taxon according to phylogenetic analysis of the rpoA gene is also P. rosenbergii (90 % similarity). The recA gene also showed low similarity T (83.7, 83.4 and 82.4%, respectively) with respect to those of Vibrio proteolyticus LMG 3772 Photobacterium leiognathii LMG 4228(T) and P. rosenbergii LMG 22223(T). Neighbour-joining phylogenetic analysis of the rpoA and recA genes confirms that strain MACL01(T) belongs to the genus Photobacterium, forming a branch together with P. rosenbergii. Strain MACL01(T) was able to grow in 0.8% NaCl. Growth occurred between 4 and 37 degrees C (optimum, 28 degrees C) and at pH 5-8.5. Luminescence was negative on marine agar. Strain MACL01(T) was found to be sensitive to the vibriostatic agent O/129. It reduced nitrate to nitrite, produced beta-galactosidase and hydrolysed gelatin, but did not produce arginine dihydrolase, indole or acetoin. Strain MACL01(T) used several carbohydrates and fermented glucose, L-arabinose and sucrose. The most abundant fatty acids were summed feature 3 (32.6%; comprising C-16:1 omega 7c and/or C-15:0 iso 2-OH), C-16:0 (21.2%) and C-18:1 omega 7c (19.9 %). The G + C content of the genomic DNA was 49.8 mol%. On the basis of genotypic, phenotypic, chemotaxonomic and phylogenetic results, strain MACL01(T) (=LMG 22194(T) =CECT 5860(T)) should be classified as the type strain of a novel species of the genus Photobacterium, for which the name Photobacterium halotolerans sp. nov. is proposed.