Role of biofilm-specific phenotype

Evidence is accumulating that the the process of attachment to surfaces and growth in a biofilms is associated with the activation and repression of genes, resulting in a biofilm-specific phenotype of the microorganisms within a biofilm community. It is assumed that this process includes the expression of a biocide-resistant phenotype in all or a subset of the biofilm cells (Mah and O Toole, 2001). Induction of this phenotype may be caused by nutrient limitation, environmental stress, exposure to sublethal amounts of biocides, high cell density or a combination of these factors. 

Other possible phenotypic changes that are discussed include decrease of membrane permeability due to alterations in membrane compositions or the upregulation of multidrug efflux pumps that could extrude biocide molecules from the cell interior (Gilbert et al., 2001 Mah and O Toole, 2001). However, additional studies are still necessary to elucidate the relevance of these mechanisms for biofilm resistance to biocides. 

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