Open AccessIsolation and characterization of large lactococcal phage resistance plasmids by pulsed‐field gel electrophoresis
Author(s) -
Prevots Fabien,
Remy Elisabeth,
Mata Mireille,
Ritzenthaler Paul
Publication year - 1994
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1994.tb06734.x
Subject(s) - plasmid , lactococcus lactis , biology , gel electrophoresis , plasmid preparation , microbiology and biotechnology , bacteriophage , bacteria , escherichia coli , dna , genetics , gene , pbr322 , lactic acid
Five phage‐resistant Lactococcus lactis strains were able to transfer by conjugation the lactose‐fermenting ability (Lac + ) to a plasmid‐free Lac − L. lactis strain. In each case, some Lac + transconjugants were phage‐resistant and contained one or two additional plasmids of high molecular mass, as demonstrated by pulsed‐field gel electrophoresis. Plasmids pPF144 (144 kb), pPF107 (107 kb), pPF118 (118 kb), pPF72 (72 kb) and pPF66 (66 kb) were characterized: they are conjugative (Tra + ), they confer a phage‐resistant phenotype and they bear lactose‐fermenting ability (Lactose plasmid) except for the last two. Plasmids pPF144, pPF107 and pPF118 resulted probably from a cointegrate formation between the Lactose plasmid and another plasmid of the donor strain, whereas pPF72, pPF66 and the Lactose plasmid were distinct in the corresponding transconjugants. Plasmids pPF72 and pPF66 produced a bacteriocin. At 30°C, the phage resistance conferred by the plasmids was complete against small isometric‐headed phage and partial against prolate‐headed phage, except for pPF107 whose phage resistance mechanism was totally effective against both types of phages, but was completely inactivated at 40°C. Restriction maps of four of the plasmids were constructed using pulsed‐field gel electrophoresis.