Effect of Bacillus subtilis BsuM restriction-modification on plasmid transfer by polyethylene glycol-induced protoplast fusion

Abstract

Polyethylene glycol (PEG)-induced cell fusion is a promising method to transfer larger DNA from one cell to another than conventional genetic DNA transfer systems. The laboratory strain Bacillus subtilis 168 contains a restriction (R) and modification (M) system, BsuM, which recognizes the sequence 5'-CTCGAG-3'. To study whether the BsuM system affects DNA transfer by the PEG-induced cell fusion between R +M + and R -M - strains, we examined transfer of plasmids pHV33 and pLS32neo carrying no and eight BsuM sites, respectively. It was shown that although the transfer of pLS32neo but not pHV33 from the R -M - to R +M + cells was severely restricted, significant levels of transfer of both plasmids from the R +M + to R -M - cells were observed. The latter result shows that the chromosomal DNA in the R -M - cell used as the recipient partially survived restriction from the donor R +M + cell, indicating that the BsuM R -M - strain is useful as a host for accepting DNA from cells carrying a restriction system(s). Two such examples were manifested for plasmid transfer from Bacillus circulans and Bacillus stearothermophilus strains to a BsuM-deficient mutant, B. subtilis RM125. Copyright © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved 325 1 December 2011 10.1111/j.1574-6968.2011.02410.x Research Letter Research Letters © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.