Analysis of plate count data of bacteria in natural environments.

Abstract

By introducing retardation time, tr, an improved equation for the colony count-incubation time relation was presented: 1n (No - N) = No - .lambda.(t - tr) where No and N are the number of cells capable of forming colony and colonies observed at time t, respectively, and .lambda. is a parameter expressing the probability of the proliferation of cells in unit time. Various data of plate count fitted better to the equation than to the original one. Corresponding to a set of plate count data well fitted to the equation, a statistical concept of bacterial population was proposed and .lambda. was assumed to define the physiological state of the population. Some samples showed negative values of retardation time, which was interpreted by the coexistence of subpopulations having different values of parameters (No, .lambda., tr), especially .lambda.