Bacillus atrophaeus DX-9 biocontrol against potato common scab involves significant changes in the soil microbiome and metabolome

Potato common scab (CS) is a worldwide disease, caused by Streptomyces spp., and its presence reduces the market value of potatoes. A nontoxic and potentially effective approach in many control strategies is the use of antagonistic microbes as biocontrol agents. In this study, Bacillus atrophaeus DX­9 was isolated and assessed for its ability to protect against CS. Through integrated metagenomic and metabolomic analyses, changes in the soil microbial community structure and soil properties were analyzed to understand the effects of Bacillus atrophaeus DX­9 on CS. These studies revealed that DX­9 inoculation could significantly decrease CS disease rate, disease index, and the number of CS pathogens, along with an increase in soil N and P content. Our metagenomic assays identified 102 phyla and 1154 genera, and DX­9 inoculation increased the relative abundances of the phyla Pseudomonadota, Chloroflexota and Gemmatimonadota. Additionally, an increase in the relative abundance of genera, such as Bradyrhizobium, Agrobacterium, and Nitrobacter, were significantly and positively correlated with soil N and P. Metabolomic analysis revealed that DX­9 inoculation significantly increased the soil levels of phytolaccoside A, 7,8­dihydropteroic acid, novobiocin, and azafrin. These compounds were enriched in microbe pathway metabolites, including xenobiotic biodegradation and metabolism, biosynthesis of other secondary metabolites, and metabolism of cofactors and vitamins. In summary, the use of Bacillus atrophaeus DX­9 against potato CS offers an alternative biocontrol method that can improve both soil microbial community and properties. This study provides insight into the potential mechanisms by which microbial inoculants can control CS disease.