Evidence for a plasmid-linked restriction-modification system in Lactobacillus helveticus

• Published in: Applied and Environmental Microbiology 1990-11, Vol.56 (11), p.3412-3419
• Main Authors: Reyes-Gavilan, C.G. de los (Instituto de Productos Lacteos de Asturias, CSIC, Villaviciosa, Spain), Limsowtin, G.K.Y, Sechaud, L, Veaux, M, Accolas, J.P
• Format: Article
• Language: English
• Subjects: BACTERIOFAGOS; Bacteriology; BACTERIOPHAGE; Biological and medical sciences; Ecology, environment; Fundamental and applied biological sciences. Psychology; Genetics; Genetics and Molecular Biology; LACTOBACILLUS; Lactobacillus helveticus; Life Sciences; Microbiology
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.56.11.3412-3419.1990

The presence of a restriction-modification (R/M) system against two bacteriophages, 328-B1 and hv, was demonstrated in three Lactobacillus helveticus strains, CNRZ 1094, CNRZ 1095, and CNRZ 1096. In addition, the burst size of phage 328-B1 in the three restrictive strains CNRZ 1094, CNRZ 1095, and CNRZ 1096 was reduced with respect to the values obtained in its propagating strain, CNRZ 328. Heating at 60 degrees C did not inactivate the R/M system. Nonrestrictive variants from CNRZ 1094 were easily obtained under several culture conditions, but treatment with novobiocin at 42 degrees C followed by storage at -20 degrees C resulted in drastic elimination of the R+/M+ phenotype from all clones tested. Electrophoretic analysis of CNRZ 1094 nonrestrictive variants revealed the concomitant loss of a 34-kb plasmid. Four EcoRI fragments from the 34-kb plasmid were cloned in the Escherichia coli vector pACYC184. The use of one or several of these fragments as probes confirmed the plasmidic location of the genes responsible for the R/M system. These probes also showed the presence of R/M plasmids in the two other restrictive strains, CNRZ 1095 and CNRZ 1096. Lactose-fermenting ability and/or proteolytic capacity was not linked to the 34-kb plasmid