sp. nov., a Al-tolerant bacterium with the ability to inhibit f. sp. isolated from rhizosphere soil of muskmelon.

A bacterial strain, designated as A6, was isolated from the rhizosphere soil of a healthy muskmelon in Wenchang, Hainan Province, China. The cells of strain A6 were Gram-negative, aerobic, short rod and motile with a single polar flagellum. Strain A6 could tolerate up to 55.0 mM Al and inhibited the growth of f. sp. which is the pathogen of muskmelon . Growth occurred at 15-37 ℃ (optimum at 30 ℃), pH 4.5-8.0 (optimum pH 6.5) and with 0-3.0 % NaCl (w/v; optimum, 0.5%). Strain A6 shared the highest 16S rRNA gene sequence similarities with Sa (98.0%), followed by ATSB10 (98.0%), 5GH9-34 (97.9%), DHG59 (97.7%), DHo (97.7%) and 5GH9-11 (97.7%). Phylogenetic trees based on 16S rRNA gene and genomic sequences indicated that strain A6 belonged to the genus and formed a subclade with Sa and ATSB10. The average nucleotide identity (ANI), average amino acid identity (AAI) and digital DNA-DNA hybridization (dDDH) values between A6 and its closely related type strains were 78.8-80.8 %, 70.0-71.7 % and 20.5-22.1 %, respectively. The sole respiratory quinone was ubiquinone-8 (Q-8). The polar lipid profile consisted of diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), two unidentified aminophospholipids (APL1-2) and three unidentified phospholipids (PL1-3). The major cellular fatty acids (≥5 %) were iso-C, C, summed feature 9 (iso-C  9 and/or C 10-methyl), iso-C, iso-C and anteiso-C. The genome size of strain A6 was 3.7 Mb with a DNA G+C content of 65.1%. Based on the phenotypic, phylogenetic, genotypic and chemotaxonomic features, strain A6 represents a novel species in the genus , for which A6 sp. nov. is proposed. The type strain is A6 (= GDMCC 1.4640 = KCTC 92542).