Time scale of the growth progress in bacterial cultures: a self-consistent choice

Abstract

An empirical model describes the behavior of an ideal microbial culture that mimics the real one. The predicted growth curve, log[N(t)], includes the onset tail of the observed sigmoid trend, while the latency phase that precedes the cell duplication is a time gap, which does not coincide with the so-called lag phase of other models. Unsolved remains the issue of the time scale: does the origin of the time scale of the experimenter coincide with that of the microbial culture? The correlation between duration of latency phase and maximum slope of the growth trend allows determination of a “true” starting point of the growth progress as the origin of the time scale of the microbial culture. Rigid shifts in the time scale of the experimenter allow alignment of the growth trends of real microbial cultures (in excess substrate, in the same medium and at the same temperature), no matter the starting population density. The time scale of the bacterial culture allows a consistent evaluation of the extent of the latency phase that can include a “negative” time span, which is supposed to deal with some basal cell metabolism not aimed at duplication. Some examples, dealing with real psychrotrophic bacterial cultures, support the model and perfect the prediction of the extent of the latency phase at various temperatures.