Identification of a Lactose Utilization and Copper Resistance Plasmid in Lactococcus lactis subsp. lactis MCL64


Abstract: Lactose negative and copper sensitive (Lac-/Cus) mutants of Lactococcus lactis subsp. lactis MCL64 were isolated after extended incubation periods at 32ºC and 37ºC. A 30.0 kb plasmid was absent in all Lac-/Cus mutants. These results showed that lactose metabolism and copper resistance were linked to the 30.0 kb plasmid in strain MCL64. Using MCL64 as a donor, the 30.0 kb plasmid transferred into Lac-/Cus recipient strains P81 and MCL64-90 with the frequencies of 4.1x10-5- 8.2x10-3 per donor cell, respectively. All transconjugants were found to be of a Lac+/ Cur phenotype.

Keywords: L. lactis subsp. lactis, lactose utilization, copper resistance, plasmid

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