DETOXIFICATION OF THE PLANT TOXIN FLUOROACETATE BY A GENETICALLY-MODIFIED RUMEN BACTERIUM

We isolated the fluoroacetate dehalogenase gene (H1), from Moraxella s pecies strain B, and placed it under the transcriptional control of a 154 bp fragment of the emt gene promoter. The promoter/gene construct was attached to the Butyrivibrio fibrisolvens shuttle vector pBHerm, a nd the resulting dehalogenase expression plasmid (pBHf) was transferre d to B. fibrisolvens OB156 by electroporation. The emt gene promoter d irected expression of dehalogenase activity in both E. coli and B. fib risolvens OB156. Cell-free lysates of the genetically modified OB156 d efluorinated 10.6 nmol fluoroacetate/min/mg protein. Growing cultures of OB156 were able to detoxify fluoroacetate in the culture medium, at the rate of 9.9 nmol/min/mg. Plasmid pBHf was retained by 100% of OB1 56 cells after 500 generations of nonselective culture. The restrictio n pattern of pBHf remained unchanged after extensive non-selective gro wth and host bacteria continued to produce active dehalogenase. The co nstruction of rumen bacteria that are able to detoxify an important na tural poison supports the feasibility of using genetically modified ru men bacteria to aid animal production.