3). Again, we did not detect any norspermidine in the spent medium. Putrescine, diamiopropane, and spermidine levels in the biofilm spent media were similar to those of shaking cultures. However, the spent media of the biofilm cultures contained approximately 2 mM cadaverine, as compared to about 3 μM cadaverine in the spent media of shaking cultures. In the static biofilm cultures, both biofilm-associated and planktonic cells can potentially contribute to extracellular cadaverine levels; therefore, the increase in cadaverine levels seen under these conditions can simply be a result of contribution

from higher numbers of cells. Alternatively, the increase in cadaverine could reflect a change in cellular physiology brought about by growth conditions used for the biofilm cultures. To differentiate between these two possibilities,

Proteasome inhibitor we calculated the ratio of the cells in the biofilm cultures to that of shaking cultures. We found that the biofilm cultures contained only 1.5- LGK-974 to 2.5-fold more cells than shaking cultures (Table S2). We conclude that the approximately 600-fold increase in extracellular cadaverine levels observed in the biofilm cultures is predominantly a result of changes to cellular physiology. Biofilms have been shown to share some characteristics with stationary-phase cultures (Beloin & Ghigo, 2005; An & Parsek, 2007). To determine whether the increased extracellular cadaverine levels was a result of stationary-phase characteristics, we quantified polyamines in the spent medium of stationary-phase shaking cultures. We found that the polyamine profiles of these media were very similar to that of log-phase

cultures and contained very low levels of cadaverine, indicating that the increased cadaverine in the spent media of biofilm cultures is a specific response to growth in the biofilm (data not shown). Overall, these results show that the increase in biofilm cell density resulting Cetuximab molecular weight from increased nspC levels is not a consequence of changes to the levels of these polyamines in the external environment. We have previously demonstrated that exogenous norspermidine increases biofilm formation and that this increase is dependent on the presence of the protein NspS (Karatan et al., 2005). NspS and MbaA are thought to constitute a signaling system that regulates biofilm formation through their effect on local or global c-di-GMP pools in response to the polyamine norspermidine. NspS is a positive regulator of biofilms as ΔnspS mutants are significantly inhibited in biofilm formation. We wanted to determine whether the NspS-dependent norspermidine sensory pathway interacts with the norspermidine synthesis pathway to regulate biofilms. To do this, we transformed pnspC into a ΔnspS mutant and first confirmed the increased NspC levels in this strain (Fig. 1a, lanes 3 and 4, Fig. S1, lanes 2 and 4).