Commercial microbiological processes frequently contain dispersed microorganisms which are heterogeneous in their age, size, and composition. Relative protein and nucleic acid contents of individual bacteria in Bacillus subtilis submerged cultures have been measured experimentally using laser flow microfluorometry. Marginal and joint population composition density data and their complex patterns of evolution during batch growth provide an impetus and emerging basis for a new generation of potentially robust mathematical models of microbial systems.

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StimmaryFlow microfluorometry, which provides detailed information on the state of a microbial population, has been employed to characterize the Bacillus subrilis population during time intervals in which significant changes in the culture amylase activity occur. Four different batch experiments have been conducted, and the influences of inoculum age, fermentation temperature, and aeration rate on microbial population dynamics and amylase activity have been examined. Relatively high rates of amylase activity increase are observed twice during the batch, first as double cells initiate sporulation and later during germination. Rapid decreases in amylase activity are observed in highly (25-50%) sporulated populations, and, in at least one experiment, during a transition from large, rounded protoplast forms to normal rod morphology. Amylase and protease activities do not follow parallel nor proportional trajectories in these 72 hr batch fermentations.

The laser flow microfluorometer (FMF) can determine the amounts of certain components in single cells at sample rates of several thousand cells per second. This technique has been employed to characterize Bacillus subtilis populations in batch fermentations with different inocula. Protein and nucleic acid distributions obtained by FMF analyses at different times during the batch have been decomposed using an optimized fit of summed subpopulation distributions. The results of these decomposition calculations, some of which have been approximately confirmed by independent microscopic observations, indicate that the relative numbers of single rods, cell chains, spores, and swollen rounded cells change dramatically during the entire fermentation including the stationary phase. The dynamics of these subpopulations may be related to secondary metabolite production.

The laser flow microfluorometer (FMF) can determine the amounts of certain components in single cells at sample rates of several thousand cells per second. This technique has been employed to characterize Bacillus subtilis populations in batch fermentations with different inocula. Protein and distributions obtained by FMF analyses at different times during the batch have been decomposed using an optimized fit of summed subpopulation distributions. The results of these decomposition calculations, some of which have been approximately confirmed by independent microscopic observations, indicate cells relative numbers of single rods, cell chains, spores, and swollen rounded cells change dramatically during the entire fermentation including the stationary phase. The dynamics of these subpopulations may be related to secondary metabolite production.