Massilia rhizosphaerae sp. nov., a rice-associated rhizobacterium with antibacterial activity against Ralstonia solanacearum

Abstract

A novel rhizobacterium, designated strain NEAU-GH312^T, with antibacterial activity against Ralstonia solanacearum was isolated from rhizosphere soil of rice (Heilongjiang Province, PR China) and characterized with a polyphasic approach. Cells of strain NEAU-GH312^T were Gram-stain-negative, aerobic, non-spore-forming, motile with peritrichous flagella and rod-shaped. Colonies were light orange, convex and semi-translucent on Reasoner's 2A (R2A) agar after 2 days of incubation at 28 °C. Growth was observed on R2A agar at 10-40 °C, pH 4.0-8.0 and with 0-5 % (w/v) NaCl. The respiratory quinone was ubiquinone Q-8. The major cellular fatty acids of strain NEAU-GH312^T were C_{16 : 1} ω7c and/or C_{16 : 1} ω6c, C_{16 : 0} and C_{18 : 1} ω7c and/or C_{18 : 1} ω6c. The main polar lipids were phosphatidylglycerol, phosphatidylethanolamine and diphosphatidylglycerol. Phylogenetic analyses confirmed the well-supported affiliation of strain NEAU-GH312^T within the genus Massilia, close to the type strains of Massilia arvi THG-RS2O^T (98.7 %), Massilia norwichensis NS9^T (98.7 %) and Massilia kyonggiensis TSA1^T (98.6 %). Strain NEAU-GH312^T had a genome size of 6.68 Mb and an average DNA G+C content of 66.3 mol%. Based on the genotypic, phenotypic and chemotaxonomic data obtained in this study, strain NEAU-GH312^T could be classified as representative of a novel species of the genus Massilia, for which the name Massilia rhizosphaerae sp. nov. is proposed, with strain NEAU-GH312^T (=DSM 109722^T=CCTCC AB 2019142^T) as the type strain.

Keywords: Massilia rhizosphaerae sp. nov.; Ralstonia solanacearum; antibacterial activity; polyphasic approach; whole genome analysis.