Monitoring transfer of recombinant and nonrecombinant plasmids between Lactococcus lactis strains and members of the human gastrointestinal microbiota in vivo--impact of donor cell number and diet.

Abstract

The generation of data of real relevance to the purported risks of DNA transfer from food-borne genetically modified microorganisms (GMMOs) using the human biota associated (HBA) rat model. Plasmid transfer between Lactococcus lactis strains and between donor strains and human gut bacteria was monitored. Transfer of the recombinant plasmid pCK1 and/or the promiscuous nonrecombinant plasmid pAMbeta1 between L. lactis strains was monitored in vivo in HBA rats. No transfer of pCK1 was observed. Transfer of pAMbeta1 was observed to Enterococcus spp. present in the HBA rats. Transconjugants persisted for 30 d and were distributed throughout the gastrointestinal tract. Both HBA rat diet and donor cell numbers impacted on transconjugant numbers. Fewer transconjugants were observed in animals fed a high-fat human type diet, while high levels of plasmid transfer were only observed at doses of donor L. lactis greater than 109 cfu. The utility of models of the human gut in monitoring DNA transfer events within the gut microbiota was demonstrated. Such findings give some confidence for the use of GMMOs with recombinant DNA borne on nonconjugative elements in fermented foods. HBA rats are a suitable model for monitoring the fate of food-borne GMMOs.