Cloning of genes encoding colicin E2 in Lactococcus lactis subspecies lactis and evaluation of the colicin-producing transformants as inhibitors of Escherichia coli O157:H7 during milk fermentation

S. M. Liu, D. M. Miller, R. F. Roberts

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2 Scopus citations

Abstract

Colicin E2 (ColE2) is a proteinaceous bacterial toxin produced by some strains of Escherichia coli and other members of the Enterobacteriaceae that exhibits inhibitory activity against some strains of E. coli O157:H7. A 2.0-kb DNA fragment, containing the ColE2 structural gene ceaB and immunity gene ceiB from E. coli NCTC 50133 (pColE2-P9), was cloned into the lactococcal plasmid vector pNZ2103. The lysis gene, celB, was not cloned. The plasmid, pLR-E2, encoding the cloned genes was transformed into E. coli DH5α and Lactococcus lactis ssp. lactis LM0230 and PN-1 using electroporation. The bacteriocin ColE2 was expressed in transformants of both E. coli and L. lactis ssp. lactis. Secretion of ColE2 into media was verified by spot-on-lawn assays and measurement of ColE2 activity in the growth medium of transformants. The level of ColE2 produced by transformants containing pLR-E2 was similar to that produced by the parental strain, E. coli NCTC 50133 (pColE2-P9). Evaluation of a ColE2-producing transformant of L. lactis ssp. lactis as a starter culture revealed that, although ColE2 was produced by transformants and could be detected in milk during fermentation, the inhibitory activity of ColE2 against E. coli O157:H7 was significantly decreased in milk compared with buffered growth medium.

Original languageEnglish (US)
Pages (from-to)1146-1154
Number of pages9
JournalJournal of dairy science
Volume94
Issue number3
DOIs
StatePublished - Mar 2011

All Science Journal Classification (ASJC) codes

  • Food Science
  • Animal Science and Zoology
  • Genetics

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