Identification of Salmonella enterica Serovar Typhimurium Genes Associated with Growth Suppression in Stationary-Phase Nutrient Broth Cultures and in the Chicken Intestine
Rychlik, I., Martin, G., Methner, U., Lovell, M., Cardova, L., Sebkova, A., Sevcik, M., Damborsky, J., Barrow, P.A.
ARCHIVES IN MICROBIOLOGY 178: 411-420 (2002)
Over 2,800 Tn5 mutants of Salmonella enterica serovar Typhimurium have been screened for the loss of ability to suppress the multiplication of a spectinomycin-resistant but otherwise isogenic S. Typhimurium strain, when this was added to 24 hour LB broth cultures of the mutants. Selected “growth non-suppressive” (GNS) mutants were defective in respiration (insertions in arcA and fnr), amino acid biosynthesis (aroA and aroD), nutrient uptake and its regulation (tdcC and crp), and in chemotaxis (fliD). In the last GNS mutant, the transposon inactivated yhjH, an ORF with unknown function which shows homology to di-guanylate cyclase and novel two-component signal transduction proteins. In newly-hatched chickens, all the mutants, with the exception of the fliD mutant, were also unable to suppress colonisation of the alimentary tract by the parent strain inoculated one day later. Defined mutations in luxS or sdiA, genes which contribute to quorum sensing in S. Typhimurium, had no effect on the stationary-phase growth suppression. A transcriptional fusion was constructed which indicated that the yhjH was moderately expressed in the exponential phase of growth and up-regulated upon entry into stationary phase. Expression of yhjH was also considerably suppressed by the addition of supernatant from a 24 hour stationary-phaseS. Typhimurium culture suggesting that it belongs to a new sensing and signalling regulatory pathway in S. Typhimurium.