Scarless Genomic Point Mutation to Construct a Strain Displaying Increased Antibiotic Plipastatin Production.

strains produce various types of antibiotics, and random mutagenesis has traditionally been used to overproduce these natural metabolites. However, this method leads to the accumulation of unwanted mutations in the genome. Here, we rationally designed a single nucleotide substitution in the gene to generate a strain displaying increased plipastatin production in a foreign DNA-free manner. The mutant strain (BS1028u) showed improved antifungal activity against . Notably, operon deletion in BS1028u resulted in complete loss of antifungal activity, suggesting that the antifungal activity strongly depends on the expression of the operon. Quantitative real-time PCR and assays showed that the point mutation resulted in 2-fold increased operon expression, which caused the increase in antifungal activity. Likewise, commercial strains can be improved to display higher antifungal activity by rationally designed simple modifications of their genome, rendering them more efficient biocontrol agents.