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Fig. 6 | BMC Microbiology

Fig. 6

From: The alternative sigma factor RpoQ regulates colony morphology, biofilm formation and motility in the fish pathogen Aliivibrio salmonicida

Fig. 6

Proposed model for regulation of QS related phenotypes in A. salmonicida. At high cell densities, LitR is produced in response to AHLs and acts as a positive regulator of rpoQ expression. LitR, probably via RpoQ, downregulates motility and expression of exopolysaccharides. The ΔlitR mutant shows a mature biofilm with mushroom shaped structures, whereas the ΔrpoQ biofilm is more flat and regular. Thus, in addition to repression of exopolysaccharides via RpoQ, LitR represses other biofilm matrix components independent of RpoQ that are required for building mature mushroom structures (e.g. lipoproteins, protein filaments). Therefore, at high cell densities both RpoQ dependent and independent processes are needed for down regulation of the mature biofilm. The ΔrpoQ mutant shows decreased motility suggesting that RpoQ may also act as a positive activator of motility. Arrows and lines with bar ends indicate pathways of positive and negative regulation, respectively, and may consist of several steps. The thicker, empty arrows indicate the resulting phenotypes

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