Effects of Different Carbon Sources on Autoinducer-2 Levels in Escherichia coli and Salmonella typhimurium During Lag, Exponential, and Stationary Growth Phases

Autoinducer signaling molecule, AI-2, is responsible for intercellular communication in quorum sensing. Growth curves were constructed for Escherichia coli DH5 α, Escherichia coli AB1157, and wild type Salmonella typhimurium LT2 grown in both glucoseand glycerol-supplemented media and AI-2 levels were determined at time points representing lag, exponential, and stationary phases of growth. Contrary to previous literature, it was found that AI-2 levels were higher during stationary phase of growth rather than midexponential phase. This was unexpected since previous literature suggested peak levels to occur during mid-exponential phase. Degradation of AI-2 molecule was not observed; we did not see a decrease in AI-2 levels over time. A significantly higher autoinducer production was recorded when the three strains were grown in glucose-supplemented media as opposed to glycerol-supplemented media. In particular, we found that the wild type S. typhimurium accumulated a significantly higher level of autoinducer. Further experimentation may be needed to extend the length of stationary phase covered by the experiment.