A simplified model for the disruption of Escherichia coli: the effect of cell septation

A new model for the disruption of Escherichia coli by high-pressure homogenization has been previously presented. Initial model development assumed a bimodal distribution of effective cell strengths to allow for a possible difference in strength between septated and nonseptated cells. A considerably simpler model is obtained when any difference in strength is neglected and a normal distribution is employed. In this article, the disruption of a culture with an abnormally high septated fraction is examined. Disruption versus pressure curves are predicted using both the bimodal and normal approximations to the strength distribution. An examination of disrupted cultures by optical and electron microscopy suggests that septated cells are indeed weaker, thus implying that a bimodal approximation is strictly correct. However, comparison of the model predictions with the experimental results suggests that the simple normal distribution provides sufficient predictive accuracy even for cultures with a high septated fraction.