The effect of O-antigen on transformation efficiency in Serratia marcescens.

Serratia marcescens is an enterobacterium that exhibits very low efficiency of transformation. According to previous work, neither the bacterium restriction system nor its nuclease production accounts for this low efficiency. Differences in the efficiency of transformation from plasmid DNA were found in wild type of S. marcescens and their O-deficient spontaneous mutant strains. This phenomenon seems to be independent of plasmid size. When electroporation was used, the survival of O-mutants was much lower than those of their parental strains, but the frequencies of transformation among survivors were much higher. This suggests that the presence of the O-antigen is responsible for the low transformation frequencies observed.