Pleomorphomonas diazotrophica sp nov., an endophytic N-fixing bacterium isolated from root tissue of Jatropha curcas L.

A novel aerobic, non-motile, pleomorphic, Gram-negative and nitrogen-fixing bacterial strain, designated R5-392(T), was isolated from surface-sterilized root tissue of Jatropha curcas. The organism grew optimally at 30 degrees C in media containing 1% (w/v) NaCl and at pH 6.0-8.0. The predominant ubiquinone was Q-10 and the major fatty acids were C-18:1 omega 7c/C-18:1 omega 6c, C-16:0 and C-19:0 cyclo omega 8c. The DNA G+C content was 63.2 mol%. Analysis of the 16S rRNA gene sequence suggested that strain R5-392(T) is affiliated with the order Rhizobiales within the class Alphaproteobacteria and is most closely related to Pleomorphomonas oryzae F-7(T) (98.8% similarity) and Pleomorphomonas koreensis Y9(T) (98.3% similarity). Analysis of partial nifH gene sequences also revealed a monophyletic lineage within the class Alphaproteobacteria, and strain R5-392(T) was most closely related to P. oryzae F-7(T) (98 %). Highest nitrogenase activity was detected in the presence of low-level organic nitrogen or in the presence of nitrogenase co-factors (Fe/Mo) in N-free media. Phenotypic and chemotaxonomic data suggest that strain R5-392(T) represents a novel species within the genus Pleomorphomonas, for which the name Pleomorphomonas diazotrophica sp. nov. is proposed. The type strain is R5-392(T) (=KACC 16233(T) =DSM 25022(T)).