Full-length single-stranded PCR product mediated chromosomal integration in intact Bacillus subtilis

A high-efficiency recombineering system with PCR-based ssDNA in Bacillus subtilis mediated by the native phage recombinase GP35

Bacillus subtilis and its closely related species are important strains for industry, agriculture, and medicine. However, it is difficult to perform genetic manipulations using the endogenous recombination machinery. In many bacteria, phage recombineering systems have been employed to improve recombineering frequencies. To date, an efficient phage recombineering system for B. subtilis has not been reported. Here, we, for the first time, identified that GP35 from the native phage SPP1 exhibited a high recombination activity in B. subtilis. On this basis, we developed a high-efficiency GP35-meditated recombineering system. Taking single-stranded DNA (ssDNA) as a recombineering substrate, ten recombinases from diverse sources were investigated in B. subtilis W168. GP35 showed the highest recombineering frequency (1.71 ± 0.15 × 10(-1)). Besides targeting the purine nucleoside phosphorylase gene (deoD), we also demonstrated the utility of GP35 and Beta from Escherichia coli lambda phage by deleting the alpha-amylase gene (amyE) and uracil phosphoribosyltransferase gene (upp). In all three genetic loci, GP35 exhibited a higher frequency than Beta. Moreover, a phylogenetic tree comparing the kinship of different recombinase hosts with B. subtilis was constructed, and the relationship between the recombineering frequency and the kinship of the host was further analyzed. The results suggested that closer kinship to B. subtilis resulted in higher frequency in B. subtilis. In conclusion, the recombinase from native phage or prophage can significantly promote the genetic recombineering frequency in its host, providing an effective genetic tool for constructing genetically engineered strains and investigating bacterial physiology.