Fig 1.
High c-di-GMP levels inhibit Salmonella motility in the absence of YcgR. Representative swimming motility plates after incubation at 23°C for 16 h are shown. Quantitative measurement of motility is also shown. The total area of growth was measured, and the percent motility relative to that of the parental strain was calculated. Means and standard deviations of results from three repeats on three separate days are shown. Overexpression of the DGC-encoding gene stm1987 in a wild-type S. Enteritidis strain (WT pBR328::stm1987) completely inhibited motility even in the absence of YcgR (ΔycgR pBR328::stm1987). Overexpression of a heterologous DGC-encoding gene, hmsT, in a multiple S. Enteritidis mutant in all genes encoding GGDEF domain proteins (ΔXII Psen4316::hmsT) also resulted in motility blockage that was only slightly restored when the ycgR gene was mutated (ΔXII ΔycgR Psen4316::hmsT). Inhibition of motility depended on the capacity of STM1987 and HmsT to synthesize c-di-GMP (see WT pBR328::stm1987-GS and ΔXII Psen4316::hmsT-GS strains, respectively).