RETENTION AND EXPRESSION OF RECOMBINANT PLASMIDS IN SUSPENDED AND BIOFILM-BOUND BACTERIA DEGRADING TRICHLOROETHENE (TCE)

Exposure of plasmid recombinant microorganisms to an open environment, either inadvertently or intentionally, requires research into those f undamental processes that govern plasmid retention, transfer and expre ssion. In the open environment, a majority of the microbial activity o ccurs associated with an interface, within thin biological layers cons isting of cells and their insoluble extracellular polymer, layers know n as biofilms. Current toxic wastewater or wastegas treatment reactors exploit bacterial biofilm systems for certain system operating advant ages. Using recombinant bacteria within a biofilm reactor to degrade x enobiotic wastes requires finding a suitable host to harbor and expres s the desired plasmid phenotype. Suitable host characteristics include : the ability to produce copious amounts of biofilm, resistance to was te-related injury and toxicity, and the ability to retain and express the desired plasmid during long term operation. This paper reports on a laboratory evaluation of factors governing plasmid retention and the expression of trichloroethene (TCE) degradative capacity in both susp ended and biofilm cultures. (C) 1997 IAWQ. Published by Elsevier Scien ce Ltd.