Quorum sensing in Escherichia coli and Salmonella typhimurium Essay

Quorum sensing in Escherichia coli and Salmonella typhimurium - Essay Example The influence of environmental factors on quorum sensing as seen by the influence of glucose metabolism on the production and degradation of the signal shows that through quorum sensing the cells communicate their growth phase as well as the metabolic potential of their environment. Strain AB 1157 of E. coli and strain LT2 of S. typhimurium grown in 0.5% glucose containing LB broth for the assay was removed from the medium and checked for activity that resulted in expression of luminescence in V. harveyi. 10% cell-free culture fluids from the two strains demonstrated maximal induction of luminescence in the V. Harveyi reporter strain BB170 which has the phenotype for quorum sensing, sensor 1-, sensor 2+ which induces luminescence exclusively through the signaling system 2 detector. The response was similar to that from V. harveyi BB152 culture fluid with E. Coli showing 106% and S. typhimurium showing 237% activity of the control activity. The signaling factor was not produced and the luminescence expression not induced when the bacterial strains were cultured in LB broth without added glucose and substitution of 10% LB medium containing glucose respectively. Candidates for signal including glucose, cAMP, amino acids, acetate, ÃŽ ±-ketogluterate, homoserine lac tone and other keto acids also produced no activity suggesting V. Harveyi BB170 respond to some signaling substance secreted by E. coli AB1157 and S. typhimurium LT2 grown on glucose containing LB medium. An analogous experiment performed with V. Harveyi reporter strain BB886 (sensor 1+ , sensor 2-) which is a wild type strain that do not act in response to signaling molecules that function through the signaling system 2 detector. Addition of E. coli AB1157 and S. typhimurium LT2 cell-free culture fluids showed only a respective 1% and 5% increase above control level (control used V. harveyi BB120 spent cultures which produces system 1 autoinducer).These results shows that E. coli AB1157 and