A biofilm treatment target was postulated to be characterized by expression late in biofilm development and at the outermost edge of the biofilm. This, too, was true for FlhD/FlhC. Expression of flhD increased again towards 51 h, the highest expression of flhD was in the outer layer of the biofilm. Based upon these results, we Trichostatin A come to the conclusion that the flagella master regulator complex FlhD/FlhC may be our first target for both, biofilm prevention and treatment techniques. This would fulfill our first two goals: i) provide proof of concept that our approach can identify targets for biofilm prevention and treatment techniques and ii) establish FlhD/FlhC as the

first such target. In fulfillment of the final goal of this study, we identified two mechanisms to increase flhD expression and reduce biofilm amounts. Mutations in the two-component response regulator genes ompR and rcsB increased flhD expression to the point where temporal and spatial differences PF-01367338 price in expression were abolished. These expression increases where paralleled by decreases in biofilm amounts, relative to the parent strain. The expression profiles of flhD, ompR, and rcsB can be related to Biofilm phases Originally described in Pseudomonas aeruginosa,

it is now widely accepted that biofilm development in many bacteria involves reversible attachment, irreversible attachment, maturation, and dispersion [31]. These phases are characterized by cell surface organelles such as flagella, type I fimbriae and curli, as well as numerous exopolysaccharides. The following three paragraphs relate the temporal expression profiles of flhD (positive regulator of flagella), ompR (negative regulator of flagella and positive

regulator of curli), and rcsB (negative regulator of flagella and positive regulator of type I fimbriae and colanic acid capsule) to current literature on biofilm developmental phases. According to our previous review [23], the hypothesis for the temporal expression profiles was that flhD expression may peak during reversible attachment, ompR expression during irreversible attachment, and rcsB expression aminophylline may increase towards maturation. A recent review article summarized the regulation of motility during biofilm formation [32]. The authors believe that flagella are important in the motility-to-biofilm transition in a way that inhibition of motility encourages biofilm formation by means of several functional (e.g. YcgR) and regulatory (e.g. RcsB) mechanisms [22, 33, 34]. Our temporal expression profile of flhD is partially in agreement with this postulate. We saw a peak in expression at 12 hours (Figure 2), which may resemble reversible attachment, and a time period of low flhD expression around 34 h, possibly resembling irreversible attachment. However, expression of flhD increased again towards 51 h (Figure 2). This late increase is not necessarily in agreement with current biofilm models.