Survie d'Escherichia coli génétiquement modifiée et mobilisation de plasmides recombinants par : des souches isolées de l'environnement ou des populations naturelles mixtes

Abstract : We studied OGMs survival and recombinant DNA (rDNA) dissemination by mobilization thanks to two experimental systems using bacterial biomass either fixed or in suspension. Initially the mobilization properties of pBR type recombinant plasmids between two strains of Escherichia coli were determined in the fixed-bed reactor. Only the mobilization of the recombinant Pce325 plasmid bearing a transfer origin was observed. A difference in fixation of donor strains could be explained by a difference in adhesion : adhesion could be influenced by plasmid copy number and by R388 plasmid (perhaps from conjugative pili). A mixture of 10 bacterial strains isolated from activated sludge was grown on a support in a continuously fed fixed-bed reactor or in suspension in a sequenced-batch reactor with biomass recycling. After reaching steady state, the bacteria in both type of reactors were used as the recipient population for evaluating the dissemination of the non-conjugative and non-mobilizable recombinant plasmide pCE328 derivated from pBR328 (tra- mob- oriT-). The dissemination of this plasmid, was studied in comparison with the natural broad host range conjugative plasmid R388 (Inc W). The survival of Escherichia coli strains bearing either the non-transferable plasmid pCE328 or the conjugative plasmid R388 and added to the activated sludge reactors was measured on the effluent of both type of reactors. In the fixed-bed reactor effluent, the donor populations remained stable after 3 days of operation and reached 10[3] to 10 [5] CFU cm-3, whereas they decreased in the sequenced-batch reactors : donors bearing the pCE328 plasmid decreased by 2 log units in 20 days, whereas those bearing R388 plasmid decreased by less than 1 log unit. Mobilization of the pCE328 plasmid could never be detected. DNA transfer between Escherichia coli strains by activated sludge mobilization on agar plate has been studied in order to assess the dissemination of pBR-type non mobilizable recombinant plasmids. The dissemination of pCE328 recombinant plasmid was compared to the one observed with the mobilizable recombinant pCE 325 PLASMID; The mobilization of pCE 325 plasmid was the only one which could be detected in presence of “helpers” plasmids R388 tra+ and pUB280 mob+ in the recipient strain. Transfer frequency was decreased by 1 log unit when activated sludge was present. Thus, pCE328 mobilization has not been determined with a detection limit reaching 10[-9] transconjugants per donors. The dissemination risk of plasmids tra- mob- oriT- in environment is not likely
Document type :
Theses
Complete list of metadatas

Cited literature [117 references]  Display  Hide  Download

https://hal.univ-lorraine.fr/tel-01777150
Contributor : Administrateur Du Ccsd <>
Submitted on : Tuesday, April 24, 2018 - 4:12:39 PM
Last modification on : Thursday, April 26, 2018 - 1:28:29 AM

File

Frank.Nadine.SMZ9641.pdf
Files produced by the author(s)

Identifiers

  • HAL Id : tel-01777150, version 1

Collections

Citation

Nadine Frank. Survie d'Escherichia coli génétiquement modifiée et mobilisation de plasmides recombinants par : des souches isolées de l'environnement ou des populations naturelles mixtes. Sciences agricoles. Université Paul Verlaine - Metz, 1996. Français. ⟨NNT : 1996METZ041S⟩. ⟨tel-01777150⟩

Share

Metrics

Record views

25

Files downloads

68