Inhibition Mechanism of Bacillus velezensis TS-2 Against Streptomyces scabies

Potato common scab is a soil-borne disease caused by Streptomyces spp., which affects the commodity value of potato worldwide. This study evaluated the inhibitory effect and potential mechanisms of the Bacillus velezensis TS-2 strain against Streptomyces scabies, providing a basis for developing safe and effective biocontrol agents for potato common scab. Strain TS-2 was isolated from soil adhering to the surface of healthy potato tubers. Confrontation assays, scanning electron microscopy, and pot experiments showed that strain TS-2 significantly reduced the potato common scab incidence and inhibited the mycelial growth and spore formation of S. scabies. Whole genome sequencing identified strain TS-2 as Bacillus velezensis. Transcriptome analysis showed that B. velezensis TS-2 significantly downregulated key genes involved in carbohydrate, lipid, and amino acid metabolism in S. scabies, including aceB, glyA, acd, thereby disrupting the core carbon and nitrogen energy supply network essential for pathogen growth and development. B. velezensis TS-2 also induced structural damage to the cell wall (pbpA), cell membrane (ino1) and bubble sac (gvpA), reducing environmental adaptability. Noticeable downregulation of genes in the bld–whi morphological differentiation cascade and the quorum-sensing gene afsA was observed under TS-2 stress, which correlates with suppressed hyphal maturation and sporulation of S. scabies.