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Genetically modified organisms in food- evaluation of in vitro and in vivo models for assessing DNA transfer in gut. - FS0204

The overall objective is to provide a means of evaluating the safety of genetically modified micro-organisms (GMOs) that may be ingested in a viable form in foods such as yoghurt, cheese, bread and beer. Both in vitro and in vivo procedures will be investigated for their suitability for such evaluation. The ability of GMOs to survive in the mammalian gut and to transfer their DNA to members of the normal human gut microflora will be assessed using novel model systems which allow the human colonic microflora to be maintained in vitro (continous flow culture) or in vivo (human flora associated rat). The influence on transfer of modified DNA of various factors such as exposure level, transit time, gut pH, bile acids and DNA homology will be studied using models. For comparitive purposes, survival and DNA transfer of microorganisms currently used in food (non-GMOs) will be assessed in the same model systems.
1) Choice of GMOs To provide baseline data, parallel studies will be performe d to assess survival of a non-genetically modified organism from the same species as the GMO and currently in use in fo od. 2) Survival of GMO's and non-GMOs and DNA transfer in an in vitro model of the human colon. (i) To establish whether currently used food microorganisms (nonGMOs and GMOs) can compete with the indigenous microflora of the human colon. (ii) To provide information on the numbers of viable GMOs and non-GMOs entering the colon needed to establish a stable population. (iii) To determine whether transfer of DNA from the GMO to members of the indigenous human colonic microflora can take place. 3) Survival of GMOs and non-GMOs and potential for DNA transfer in an in vivo model of the human colonic microflora. (i) To establish whether GMOs and non-GMOs can survive passage through the upper regions of the mammalian gastro-intestinal tract. (ii) To determine whether the organism can compete with the human colonic flora in vivo and establish itself within the gut and/or how long it can persist in the intestinal environment. (iii) To determine the level of intake of GMOs required to establish a stable population in the colon. (iv) To determine whether transfer of DNA from the GMO to members of the indigenous human colonic microflora can take place in vivo. 4) Factors affecting DNA transfer in the gut. (i) To investigate the level of exposure to GMO in vitro and then in vivo as part of objectives 2 and 3 above. (ii) To investigate gut pH over a range of physiological pH concentrations observed in the human colon. (iii) To establish the effects of bile acids on DNA transfer the concentration of bile acids added to the in vitro model will be varied within the range observed in human faeces. (iv) To investigte the effect of altering the dilution rate of the culture on the growth rate of the bacteria.
Time-Scale and Cost
From: 1995

To: 1998

Cost: £242,977
Contractor / Funded Organisations
BIBRA Toxicology International