Transfer of the shuttle vector pRRI207 between Escherichia coli and Bacteroides spp. in vitro and in vivo in the digestive tract of axenic mice and in gnotoxenic mice inoculated with a human microflora

Transfer of the shuttle vector pRRI207 mediated by the helper plasmid pRK20 13 from Escherichia coli to Bacteroides spp. was possible in vitro and in v ivo in the digestive tract of axenic mice associated with Bacteroides unifo rmis 1004 or Bacteroides vulgaris of human origin. In vivo, transfer freque ncies were nearly identical for B. uniformis (2 x 10(-7)) and B. vulgatus ( 4 x 10(-7)) and the transconjugant strains of B. uniformis and B. vulgatus became established in the digestive tract of mice at densities ranging from 10(2)-10(3) to 10(4) CFU g(-1) of faeces, respectively. Transfer from E. c oli to Bacteroides strains in gnotoxenic mice associated with human faecal flora (HFF) was not successful. Transconjugant-like clones appeared among t he HFF of gnotoxenic mice after they were inoculated with B. uniformis TBUA , a transconjugant strain of B. uniformis 1004 obtained from triparental ma ting and which harboured the shuttle vector. Hybridisation showed that the shuttle Vector pRRI207 was not present in these clones, and it is suggested that they could result from the transfer of a conjugative transposon ERL c ontained in B. uniformis 1004. Moreover, clones believed to have lost the s huttle vector hybridised with a specific probe to B. thetaiotaomicron and t herefore did not originate from B. uniformis TBUA. (C) 1999 Federation of E uropean Microbiological Societies. Published by Elsevier Science B.V. All r ights reserved.