sacA and nisA genes are not always linked in Lactococcus lactis subsp. lactis strains

Sixty-seven lactococcal strains arising from dairy habitat were screened fo r the presence of the sucrose 6-phosphate hydrolase gene by polymerase chai n reaction. Of the strains tested, 35.8% were able to ferment sucrose as we ll as to harbour the sucrose-6-phosphate hydrolase gene, even though they w ere unable to produce nisin as well as to show the nisin structural gene. A fter pulsed-field gel electrophoresis and hybridisation all Suc(+) Nis(-) s trains exhibited physical linkage between sacA gene and the left end of lac tococcal transposons (Tn5276 or Tn5301) without linkage to nisin genes. How ever, we were unable to transfer the sacA gene as well as to detect Suc(-) derivatives from Suc(+) Nis(-) strains after conjugation and curing experim ents. (C) 1999 Published by Elsevier Science B.V. All rights reserved.