General investigation of PBSX-like defective prophages resident in Bacillus subtilis strains

Abstract:

[Objective] To investigate PBSX-like defective prophages resident in 39 Bacillus subtilis strains preserved in China Center for Type Culture Colletion (CCTCC). [Methods] B. subtilis strains were induced with mitomycin C, yielding cell lysate supernatants. Agarose gel electrophoresis was used to detect the existence of 13 kb DNA fragments in cell lysate supernatants. Cell lysate supernatants were mixed with PBSX-sensitive strain, B. subtilis W23 to determine the killing activity against W23. Phage-like particles in the cell lysate supernatants were examined with transmission electron microscopy. [Results] Cell lysate supernatants of 24 strains were detected to have 13 kb DNA fragments, and had killing activity against W23. They were defined as PBSX lysogenic bacteria. 1 strain’s lysate supernatants possessed 13 kb DNA fragments, but had no killing activity against W23. 5 strains’ lysate supernatants displayed killing activity against W23 although 13 kb DNA fragments were not detected in them. 9 strains’ lysate supernatants did not have 13 kb DNA fragments, as well as had no killing activity against W23. Among the 9 strains, 3 strains’ lysate supernatants were detected to have phage-like particles distinguished with PBSX. [Conclusion] Among the 39 B. subtilis strains, 61.5% are PBSX lysogenic bacteria. Industrial strains and wild strains isolated from soil collected from Shennongjia harbor various phage-like particles distinguished from PBSX. Results in this paper provide more theory evidences for further uncovering the function of PBSX on host bacteria.