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

Abstract

A halotolerant bacterium was isolated from a saline lake located in Mallorca, Spain. Cells of the strain, designated MACL01T, were Gram-negative, rod-shaped and motile by means of polar flagella. Colonies of strain MACL01T 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 MACL01T 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 (83.7, 83.4 and 82.4 %, respectively) with respect to those of Vibrio proteolyticus LMG 3772T, Photobacterium leiognathii LMG 4228T and P. rosenbergii LMG 22223T. Neighbour-joining phylogenetic analysis of the rpoA and recA genes confirms that strain MACL01T belongs to the genus Photobacterium, forming a branch together with P. rosenbergii. Strain MACL01T was able to grow in 0–8 % NaCl. Growth occurred between 4 and 37 °C (optimum, 28 °C) and at pH 5–8.5. Luminescence was negative on marine agar. Strain MACL01T was found to be sensitive to the vibriostatic agent O/129. It reduced nitrate to nitrite, produced β-galactosidase and hydrolysed gelatin, but did not produce arginine dihydrolase, indole or acetoin. Strain MACL01T used several carbohydrates and fermented glucose, l-arabinose and sucrose. The most abundant fatty acids were summed feature 3 (32.6 %; comprising C16 : 1 ω7c and/or C15 : 0 iso 2-OH), C16 : 0 (21.2 %) and C18 : 1 ω7c (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 MACL01T (=LMG 22194T=CECT 5860T) 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.