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.

► Bacterial growth directly correlated with SA/V ratio (surface area to culture volume). ► The effect of SA/V could be explained by inhibition of growth by endogenous CO2. ► The secretion kinetics of virulence-associated proteins indicated induction by CO2. ► Endogenous CO2 is postulated to inhibit growth and induce virulence gene expression.