Comparison of retention and expression of recombinant plasmids between suspended and biofilm-bound bacteria degrading tce

Abstract

Any exposure of plasmid recombinant microorganisms to an open system environment, either inadvertently or intentionally, mandates research into those fundamental organism:plasmid processes that influence plasmid retention, transfer, and expression. In the open environment, a majority of the microbial activity occurs associated with an interface, within thin biological layers consisting of the cells and their insoluble extracellular polymer; layers known as biofilms. In addition, current toxic wastewater or wastegas treatment reactors exploit bacteria biofilms for certain system operating advantages. Thus any study regarding the fate of recombinant DNA sequences in either an open environment or closed reactor system must consider processes that impact plasmid retention and expression in a biofilm culture. Using recombinant bacteria within a biofilm reactor to degrade a recalcitrant waste requires finding a suitable host to harbor and express the desired degrading plasmid phenotype. Suitable host characteristics include: ability to produce copious amounts of biofilm, resistance to waste-related injury and toxicity, and 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 TCE degradative capacity in both suspended and biofilm cultures.