Characterization of Bacillus subtilis phages PJNB030, PJNB031, and PJNB032 reveals wall teichoic acid as a key...

Bacillus subtilis is widely used in industrial fermentation and probiotic applications; however, phage contamination poses a substantial economic threat. To address this, we isolated three phages (PJNB030, PJNB031, and PJNB032) from a contaminated B. subtilis fermentation broth and characterized their biological properties. Phenotypic analyses indicated broad pH stability (pH 4-10), variable thermal tolerance, and differential UV sensitivity. Replication kinetics revealed latent periods of 10-20 min and burst sizes ranging from 50 to 73 PFU/cell. Genomic sequencing identified linear dsDNA genomes (64-165 kb) with GC content ranging from 33.5 to 47.4%. Phylogenomic and comparative genomic analyses revealed that these phages were located on distinct branches. Deletion of pgcA (which encodes α-phosphoglucomutase) rendered cells completely resistant to PJNB031 and PJNB032, whereas it reduced PJNB030 infectivity (plaque formation efficiency) by approximately six orders of magnitude. Adsorption assays confirmed that the binding of PJNB031 and PJNB032 to ΔpgcA mutants was abolished, whereas PJNB030 retained partial adsorption capacity. In conclusion, this study identified wall teichoic acid as the primary receptor for these phages and established pgcA deletion as an effective strategy for engineering phage-resistant B. subtilis strains. Our findings provide critical insights into the mitigation of phage contamination in industrial bioprocesses.