A novel procedure is proposed for determining distributions of rate properties and correlations of rate with state properties of microbial cell populations. The procedure is novel in that it uses transient data, and thus, it does not require that the population be in balanced growth, although it requires that the population structure does not change during the short transient experiment. The procedure is applied to populations of the ciliated protozoan Tetrahymena to determine ingestion rate variability. The number of ingested microspheres per cell and the single-cell protein content-an indicator of cell size-were directly determined with dual-color flow cytometry. The proposed technique revealed the correlation pattern of the particle ingestion rate with cell size. In particular, ingestion rate was found to be positively correlated with cell size for the smaller feeding cells and to be uncorrelated with size for the larger cells. Using the fact that particle uptake from dilute particle suspensions is a Poisson random process, we determined that the coefficient of variation of the distribution of ingestion rates within the feeding population is about 50%. It was concluded that the dynamics of particle ingestion can be accurately described only if it is realized that particle ingestion rates are distributed.
Slit‐scanning flow cytometry allows analysis of the locations of components along the long axes of cells. This is useful in determining how the components of a dividing cell are partitioned into the two daughter cells. Ciliated protozoa, unlike most eukaryotic cells, do not partition their DNA equally between daughter cells. We have used slit‐scanning flow cytometry to measure the distribution of this unequal DNA partitioning in the ciliate Tetrahymena pyriformis. Our results show that the difference in the amounts of DNA alloted to sister nuclei varies from cell to cell but, on the average, increases with the DNA content of the mother cell. However, the average difference in the fraction of the mother cell DNA partitioned to each daughter cell is more or less independent of the DNA content of the mother cell and is about 8.5% of that DNA content. Slit‐scanning flow cytometry also allows determination of the DNA distributions of dividing and newborn cells, determinations that are difficult to make with good statistical precision by other means. The measured newborn and dividing cell DNA distributions are broad, and this must be the result of repeated rounds of unequal partitioning of DNA.
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