Previous Article | Next Article ![]()
Appl. Environ. Microbiol., 04 1997, 1434-1440, Vol 63, No. 4
M Coakley, G Fitzgerald and RP Ros
The conjugative 63-kb lactococcal plasmid pMRC01 encodes bacteriophage
resistance and production of and immunity to a novel broad-spectrum
bacteriocin, designated lacticin 3147 (M.P. Ryan, M.C. Rea, C. Hill, and
R.P. Ross, Appl. Environ. Microbiol. 62:612-619, 1996). The phage
resistance is an abortive infection mechanism which targets the phage-
lytic cycle at a point after phage DNA replication. By using the genetic
determinants for bacteriocin immunity encoded on the plasmid as a
selectable marker, pMRC01 was transferred into a variety of lactococcal
starter cultures to improve their phage resistance properties. Selection of
resulting transconjugants was performed directly on solid media containing
the bacteriocin. Since the starters exhibited no spontaneous resistance to
the bacteriocin as a selective agent, this allowed the assessment of the
transfer of the naturally occurring plasmid into a range of dairy starter
cultures. Results demonstrate that efficient transfer of the plasmid was
dependent on the particular recipient strain chosen, and while
high-frequency transfer (10(-3) per donor) of the entire plasmid to some
strains was observed, the plasmid could not be conjugated into a number of
starters. In this study, transconjugants for a number of lactococcal
starter cultures which are phage resistant and bacteriocin producing have
been generated. This bacteriocin-producing phenotype allows for control of
nonstarter flora in food fermentations, and the phage resistance property
protects the starter cultures in industry. The 63-kb plasmid was also
successfully transferred into Lactococcus lactis MG1614 cells via
electroporation.
Copyright © 1997, American Society for Microbiology
Application and evaluation of the phage resistance- and bacteriocin- encoding plasmid pMRC01 for the improvement of dairy starter cultures
National Dairy Products Research Centre, Fermoy, County Cork, Ireland.
This article has been cited by other articles:
| J. Bacteriol. | Microbiol. Mol. Biol. Rev. | Eukaryot. Cell | All ASM Journals |
|---|