Isolation, identification, and whole genome sequencing of a Bacillus halotolerans strain inhibiting Phytophthora nicotianae

Abstract:

[Background] Tobacco black shank is a soil-borne diseases caused by Phytophthora nicotianae. This disease exhibits a high incidence and severity in tobacco cultivation regions across China, leading to substantial yield losses. [Objective] To screen the strains with antagonistic activity against Phytophthora nicotianae and provide strain resources for the biocontrol of tobacco black shank. [Methods] The dilution-plate spreading method and the plate confrontation method were employed to screen the strains with antagonistic effects on Phytophthora nicotianae. Whole genome sequencing of the antagonistic strain was performed on the DNBSEQ and PacBio platforms, and antiSMASH online was used for the prediction of synthetic gene clusters of secondary metabolites. [Results] Bacillus halotolerans BY-S2, a strain capable of inhibiting the growth of P. nicotianae, was isolated. Strain BY-S2 exhibited phosphorus-solubilizing ability, siderophore- producing ability, and tolerance to copper. Whole genome sequencing revealed that the genome of strain BY-S2 was a circular chromosome with a length of 4 058 008 bp and the G+C content of 43.78%. A total of 10 synthetic gene clusters of secondary metabolites were predicted by antiSMASH, including 5 completely consistent with known gene clusters for the synthesis of bacillaene, fengycin, bacillibactin, subtilosin A, and bacilysin. [Conclusion] B. halotolerans BY-S2 exhibits antagonistic activity against P. nicotianae, has the ability to solubilize phosphate and produce siderophores, and carries 5 known gene clusters of secondary metabolites.

Key words:Bacillus halotolerans;tobacco black shank;growth-promoting effect;whole genome sequencing