Pseudoalteromonas rhizosphaerae sp. nov., a novel plant growth-promoting bacterium with potential use in phytoremediation

Strain RA15(T) was isolated from the rhizosphere of the halophyte plant Arthrocnemum macrostachyum growing in the Odiel marshes (Huelva, Spain). RA15(T) cells were Gram stain-negative, non-spore-forming, aerobic rods and formed cream-coloured, opaque, mucoid, viscous, convex, irregular colonies with an undulate margin. Optimal growth conditions were observed on tryptic soy agar (TSA) plates supplemented with 2.5% NaCl (w/v) at pH 7.0 and 28 degrees C. although it was able to grow at 4-32 degrees C and at pH values of 5.0-9.0. The NaCl tolerance range was from 0 to 15%. The major respiratory quinone was Q8 but Q9 was also present. The most abundant fatty acids were summed feature 3 (C-16:1, omega 7c and/or C-16:1, omega bc), C-17:1 omega 8c and C-16:0. The polar lipids profile comprised phosphatidylglycerol and phosphatidylethanolamine as the most abundant representatives. Phylogenetic analyses confirmed the well-supported affiliation of strain RA15(T) within the genus Pseudoalteromonas, close to the type strains of Pseudoalteromonas neustonica, Pseudoalteromonas prydzensis and Pseudoalteromonas mariniglutinosa. Results of comparative phylogenetic and phenotypic studies between strain RA15(T) and its closest related species suggest that RA15(T) could be a new representative of the genus Pseudoalteromonas, for which the name Pseudoalteromonas rhizosphaerae sp. nov. is proposed. The type strain is RA15(T) (=CECT 9079(T) =LMG 29860(T)). The whole genome has 5.3 Mb and the G+C content is 40.4mol%.