Evidence for the presence of restriction/modification systems inLactobacillus delbrueckii

Abstract

The bacteriophages Cb1/204 and Cb1/342 were obtained by induction from the commercial strainLactobacillus delbrueckiisubsp.lactisCb1, and propagated onLactobacillus delbrueckiisubsp.lactis204 (Lb.l204) andLactobacillus delbrueckiisubsp.bulgaricus342 (Lb.b342), respectively. By cross sensitivity, it was possible to detect a delay in the lysis ofLb.l204 with Cb1/342 phage, while the adsorption rate was high (99·5%). Modified and unmodified phages were isolated using phage Cb1/342 and strainLb.l204. The EOP (Efficiency of Plaquing) values for the four phages (Cb1/204, Cb1/342, Cb1/342modified and Cb1/342unmodified) suggested that an R/M system modified the original temperate phage, and theBglII-DNA restriction patterns of these phages might point out the presence of a Type II R/M system. Also, the existence of a Type I R/M system was demonstrated by PCR and nucleotide sequence, being the percentages of alignment homology with Type I R/M systems reported previously higher than 95%. In this study it was possible to demonstrate that the native phage resistant mechanisms and the occurrence of prophages in commercial host strains, contribute strongly to diversify the phage population in a factory environment.