Pseudomonas citri sp. nov., a potential novel plant growth promoting bacterium isolated from rhizosphere soil of citrus.

Abstract

A novel potential plant growth promoting bacterium, designated OPS13-3T, was isolated from rhizosphere soil of citrus in Aotou Town of Guangzhou, Guangdong Province, PR China. It showed high ability to dissolve insoluble inorganic phosphate and organic phosphorus and to produce 3-indoleacetic acid (IAA) and siderophore. Cells of the novel strain were Gram-stain-negative, rod-shaped, aerobic and motile with polar flagellum. It shared the highest 16S rRNA gene similarity with Pseudomonas mucoides CCUG 74874T (98.7%) and P. bijieensis LMG 31948T (98.7%). Phylogenetic analyses based the 16S rRNA gene and genome sequences revealed that strain OPS13-3T belonged to the genus Pseudomonas, and was most closely related to P. mediterranea ICMP 14184T and P. corrugate ICMP 5819T. The average nucleotide identity (ANI) and DNA-DNA hybridization (dDDH) values between the novel strain and closely relatives with high 16S rRNA gene similarities were 80.8‒87.5% and 24.7‒34.6%, respectively, which were much below the threshold values for species delimitation. The major fatty acids included C16:0, C10:0 3-OH and summed feature 3 (C16:1ω7c and/or C16:1ω6c). It took ubiquinone 9 as the predominant respiratory quinone and the polar lipids contained phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), three unidentified phospholipids, an unidentified aminophospholipid and an unidentified lipid. Based on the phylogenetic, phenotypic and chemotaxonomic analyses and genome comparison, strain OPS13-3T should be considered as a novel species of the genus Pseudomonas, for which the name Pseudomonas citri sp. nov. is proposed (type strain OPS13-3T = GDMCC 1.3118T = JCM 35385T).