Determination of cellular rate distributions in microbial cell populations: Feeding rates of ciliated protozoa

Abstract

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.

Analysis of the distribution of ingested bacteria in nanoflagellates and estimation of grazing rates with flow cytometry

“…Even the more robust negative binomial model no longer provided acceptable fit when the right tail of the distribution was allowed to further develop with longer incubation times. Loss of acceptance of these relatively simplistic models supports the findings of Hatzis et al (1990Hatzis et al ( , 1993b that suggest the use of more complex models to describe the distribution of fluorescent microspheres in the ciliate Tetrahymena. When Tetrahymena was offered fluorescent microspheres as the only available prey, individual cell grazing was described by a Poisson (Gerritsen et al 1987, Hatzis et al 1990, 1993b, Table 4.…”

“…Loss of acceptance of these relatively simplistic models supports the findings of Hatzis et al (1990Hatzis et al ( , 1993b that suggest the use of more complex models to describe the distribution of fluorescent microspheres in the ciliate Tetrahymena. When Tetrahymena was offered fluorescent microspheres as the only available prey, individual cell grazing was described by a Poisson (Gerritsen et al 1987, Hatzis et al 1990, 1993b, Table 4. Paraphysomonas vestita and prey abundances, distribution of ingested microspheres based on cytometry histograms, and grazing rates based on cytometry frequency distributions and cytometry probability of zero [Poll,] curves.…”

“…Sample Grazers ml-' (x104) Prey rnl-' (x107) while populations with individual variability were described by compound Poisson distributions that are more complex than the negative binomial (Hatzis et al 1990(Hatzis et al , 1993b. However, with recognition that the theoretical implications of the simple Poisson distribution used by Gonzalez (1999) and the Poisson EZ used for the cytometry method of this study may not be correct, rough fit of samples to these distributions may allow use of faster methods for estimating bacterivory.…”

Selective Synchronization of Tetrahymena pyriformis Cell Populations and Cell Growth Kinetics during the Cell Cycle

“…The enumeration of several T. pyriformis culture samples before and after separation has revealed that the recovered nonfeeding populations have a cell concentration as high as 5.1% of the original culture when centrifugation of 300 g was applied. A fraction of 14.1% total nonfeeders was reported previously for the same strain growing with an average generation time of 6.4 h (16). The time spans of the two nonfeeding phases, before and after the cell division, were also determined by Hatzis (16) to be 23 and 34 min, respectively, using the technique of labeling feeding cells with fluorescent microspheres.…”

Survival of Campylobacter jejuni in Waterborne Protozoa

“…During this research, protozoa were grown for 3 days, starved, and then placed in low-nutrient conditions to replicate the low-nutrient conditions in water systems, minimize protozoa variation in feeding behavior, and increase protozoan ingestion of Campylobacter (29,30,68). A. castellanii organisms were grown for 3 days in 20 ml of proteose peptone glucose broth (CCAP) at 25°C to a population density of 10 6 cells ml Ϫ1 .…”