Endogenous CO2 may inhibit bacterial growth and induce virulence gene expression in enteropathogenic Escherichia coli.

Analysis of the growth kinetics of enteropathogenic Escherichia coli (EPEC) revealed that growth was directly proportional to the ratio between the exposed surface area and the liquid culture volume (SA/V). It was hypothesized that this bacterial behavior was caused by the accumulation of an endogenous volatile growth inhibitor metabolite whose escape from the medium directly depended on the SA/V. The results of this work support the theory that an inhibitor is produced and indicate that it is CO2. We also report that concomitant to the accumulation of CO2, there is secretion of the virulence-related EspB and EspC proteins from EPEC. We therefore postulate that endogenous CO2 may have an effect on both bacterial growth and virulence.