eng Science and Education Publishing Journal of Applied & Environmental Microbiology 2373-6712 2022-10-13 10 1 35 42 10.12691/jaem-10-1-4 JAEM20221014 article Alberto Schiraldi alberto.schiraldi@unimi.it 1 Formerly at the Department Food Environmental and Nutritional Sciences (DeFENS), University of Milan, Italy The collective behavior of microbial cells in a batch culture is the result of interactions among individuals and effects of the surrounding medium, which changes during the growth progress. A semi empirical model skips biological and physiological peculiarities of the microorganisms and focuses on the observed sigmoid shape of the growth curve that is a common feature of batch cultures of pro- and eukaryotic microorganisms. The model replaces the observed growth trend with the behavior of an ideal batch culture that undergoes an unperturbed duplication process. It leads one to recognize that: the origin of the time scale for the microbes, , differs from that of the observer, t; the absolute reference state for any batch culture is log (N) = 0 (no matter the log base) for = 0; the cell duplication occurs after an active latency gap, 0, that decreases with increasing inoculum population, log2(N0) and increasing temperature; 0 substantially differs from the lag phase, , considered by most authors; the use of reduced variables allows gathering different growth curves in a single master plot; the model applies to batch cultures which undergo change of the environmental conditions and predicts the width of the intermediate latency gap just after the change; the expression for the decay trend of the microbial population allows definition of a parameter suitable to rank the effects of bactericidal drugs. The model justifies the demand of more restricted safety limits of microbial loads. http://pubs.sciepub.com/jaem/10/1/4/jaem-10-1-4.pdf predictive model batch cultures latency gap time scale