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Abstract

Plasmid transfer occurs in the digestive tract and the transconjugants may become durably established. The aim of the present work is to investigate the effect of probiotics of plasmid transfer and on establishment of transconjugants in the gut. Plasmid transfers were carried out in the digestive tract of germ free mice associated with an E. coli K12 donor strain harboring three plasmids (R388, self-transmissible, pCE325 and pUB2380, mobilisable,) and an E. coli recipient strain, PG1, of human origin (Duval-Iflah et al., 1994). Milks fermented with either Lactobacillus bulgaricus or Streptococcus thermophilus or symbiosis, S85, of both strains were given daily as 1/3 of food diet. Fermented milks have no effect on the transfer of R388 and pUB2380 except a slight increase of TC(R388) with milk fermented with S85. Long term ingestion of milk fermented with S85 inhibited the formation and the establishment of transconjugants TC(pCE325). Milk fermented with L. bulgaricus lowered the population density of TC(pCE325) in animals where they were already established. This phenomenon was reversible, since the density of TC(pCE325) increased in the same animals after cessation of supplementation. Bacterial cultures obtained in MRS broth and given in state of drinking water were compared with fermented milks. Bacterial cultures with L. bulgaricus and with S85 favoured the establishment of TC(pCE325). There results indicate for the first time that probiotics have various effects on the formation and/or establishment of transconjugants in the gut of axenic mice. The effects depend on whether the probiotics were cultivated in milk or in MRS, indicating that bacterial metabolites and viable bacteria can be involved.

Multiscale Evolutionary Dynamics of Host-Associated Microbiomes

“…Interestingly, diet has been shown to affect the mobilization rate of certain plasmids in rats with a high fat diet reducing the rate of plasmid transfer relative to a more conventional rat chow diet (Tuohy et al, 2002). Fermented foods have also been shown to affect the density of transconjugants in germ-free mice, though it’s unknown whether this effect is due to an increase in the growth rate of the transconjugants or an increase in the mobilization rate itself (Duval-Iflah et al, 1998). The capacity for horizontal gene transfer may also be explored synthetically in “forced HGT” experiments, where genes from one microbe are transferred en masse on cloning vectors to another, and selecting for more fit transformants via passage through the mouse gut.…”

Evolutionary, ecological and biotechnological perspectives on plasmids resident in the human gut mobile metagenome

“…In this context it is of note that for certain plasmids, changes in host diet have been found to have a significant impact on rates of plasmid transfer 103 , 184 . While the GIT may provide a relatively steady source of nutrients overall, natural variation in diet means this is unlikely to be completely consistent, and when considered in terms of the complexity and niche specialization that exists in this community, it seems unlikely that all members will receive a steady and constant supply of readily utilizable nutrients.…”