The effect of reuterin on the lag time of single cells of Listeria innocua grown on a solid agar surface at different pH and NaCl concentrations.

The lag time of single cells of Listeria innocua grown on the surface of Brain Heart Infusion Agar was studied by microscopy and image analysis. An experimental set-up that enabled relocation of the cells on the agar surface was developed and used to collect data from 50 to 100 individual cells at a time. Reuterin was added at different concentrations (0-10 AU/ml) and it was observed that it increased both the lag time of the cells and its variance. Furthermore, for a large proportion of cells, reuterin completely prevented the cell division within the time of observation. Reuterin in combination with low pH inhibited the cell division even more efficiently. A similar effect was observed for the combination of reuterin and sodium chloride. Our experimental set-up provides a good model system for generating data on the lag time of single cells on solid surfaces, which can improve the predictions of microbial growth on solid food matrices.