Correlation between phenotypes of restriction / modification systems and efficiency of transformation in Campylobacter jejuni

We evaluated the effect of restriction and modification genes expressed in Campylobacter jejuni, a naturally competent organism, on transformation efficiency. Fourteen strains of C. jejuni were tested for sensitivity to 29 restriction enzymes. Strains that showed the same susceptibility pattern by either agarose gel electrophoresis or PFGE were grouped together. Natural transformation between strains within and between groups was assessed using two chromosomal markers, one an artificially introduced gene and the other a selected point mutation. However, no correlation was found between transformation efficiency and sensitivity to the restriction enzymes tested. The activity of the restriction and modification system alone could not explain the failure of transformation to occur or the generation of stable clones in a population of C. jejuni with other abilities. It is likely that other factors influence horizontal gene flow in this organism. We suggested that the rule that the restriction and modification system affect horizontal gene flow, based on studies of transfection with E. coli, may not apply to the exchange of chromosomal DNA in C. jejuni.