Integrated conjugal plasmid pLS20 in the Bacillus subtilis genome produced 850-kbp circular subgenomes transmissible to another B. subtilis

Bacillus subtilis was engineered to produce circular subgenomes that are directly transmittable to another B. subtilis. The conjugational plasmid pLS20 integrated into the B. subtilis genome supported not only subgenome replication but also transmission to another B. subtilis species. The subgenome system developed in this study completes a streamlined platform from the synthesis to the transmission of giant DNA by B. subtilis.

Biocontrol of bacterial wilt disease in tomato using Bacillus subtilis strain R31

Bacterial wilt disease caused by Ralstonia solanacearum is a widespread, severe plant disease. Tomato (Solanum lycopersicum), one of the most important vegetable crops worldwide, is particularly susceptible to this disease. Biological control offers numerous advantages, making it a highly favorable approach for managing bacterial wilt. In this study, the results demonstrate that treatment with the biological control strain Bacillus subtilis R31 significantly reduced the incidence of tomato bacterial wilt. In addition, R31 directly inhibits the growth of R. solanacearum, and lipopeptides play an important role in this effect. The results also show that R31 can stably colonize the rhizosphere soil and root tissues of tomato plants for a long time, reduce the R. solanacearum population in the rhizosphere soil, and alter the microbial community that interacts with R. solanacearum. This study provides an important theoretical basis for elucidating the mechanism of B. subtilis as a biological control agent against bacterial wilt and lays the foundation for the optimization and promotion of other agents such as R31.

Effective plasmid delivery to a plasmid-free Bacillus natto strain by a conjugational transfer system

In this study, a Bacillus natto strain named NEST141 was constructed. The strain carries no plasmids and is an authentic proline auxotroph-a feature that confers effective selection conditions for plasmids transferred from a donor, such as B. subtilis 168, via a pLS20-based conjugational transfer system. We have provided a standard effective protocol for the delivery of plasmids larger than 50 kilobase pairs. These results indicate that the B. natto NEST141 strain can become a standard model, like B. subtilis 168, for extensive genetic engineering with diverse applications.