Dyella aluminiiresistens sp. nov., a Al3+-tolerant bacterium with the ability to inhibit Fusarium oxysporum f. sp. melonis isolated from rhizosphere soil of muskmelon.

Abstract

A bacterial strain, designated as A6^T, was isolated from the rhizosphere soil of a healthy muskmelon in Wenchang, Hainan Province, China. The cells of strain A6^T were Gram-negative, aerobic, short rod and motile with a single polar flagellum. Strain A6^T could tolerate up to 55.0 mM Al³⁺ and inhibited the growth of Fusarium oxysporum f. sp. melonis, which is the pathogen of muskmelon Fusarium wilt. 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^T shared the highest 16S rRNA gene sequence similarities with Dyella lutea Sa^T (98.0%), followed by Dyella thiooxydans ATSB10^T (98.0%), Frateuria edaphi 5GH9-34^T (97.9%), Dyella nitratireducens DHG59^T (97.7%), Frateuria defendens DHo^T (97.7%) and Frateuria soli 5GH9-11^T (97.7%). Phylogenetic trees based on 16S rRNA gene and genomic sequences indicated that strain A6^T belonged to the genus Dyella and formed a subclade with Dyella lutea Sa^T and Dyella thiooxydans ATSB10^T. The average nucleotide identity (ANI), average amino acid identity (AAI) and digital DNA-DNA hybridization (dDDH) values between A6^T 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_17 : 0, C_16 : 0, summed feature 9 (iso-C_17 : 1  ω9c and/or C_16 : 0 10-methyl), iso-C_15 : 0, iso-C_16 : 0 and anteiso-C_17 : 0. The genome size of strain A6^T was 3.7 Mb with a DNA G+C content of 65.1%. Based on the phenotypic, phylogenetic, genotypic and chemotaxonomic features, strain A6^T represents a novel species in the genus Dyella, for which Dyella aluminiiresistens A6^T sp. nov. is proposed. The type strain is A6^T (= GDMCC 1.4640^T = KCTC 92542^T).