A discrete, stochastic model for microbial filter feeding: a model for feeding of ciliated protists on spatially uniform, nondepletable suspensions

Sweeney, Pamela J.; Srienc, Friedrich; Fredrickson, A. G.

doi:10.1016/0025-5564(90)90060-c

Cited by 8 publications

(6 citation statements)

References 42 publications

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“…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.…”

Section: Discussionmentioning

confidence: 55%

“…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.…”

Section: Discussionmentioning

confidence: 55%

“…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.…”

Section: Discussionmentioning

confidence: 99%

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

Bratvold¹,

Srienc

Taub³

2000

Aquat. Microb. Ecol.

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The distribution of ingested bacteria in nanoflagellates was assessed to suggest whether or not there are subgroups of grazers with different grazing rates. Several discrete random distributions were compared to the distribution of ingested fluorescently labeled bacteria (FLB) in cultures of Rhynchomonas nasuta and Paraphysomonas vestita. Sample distributions typically fit both the Poisson with extra zeros (Poisson EZ, tested as a truncated Poisson) and negative binomial, but only occasionally fit a Poisson. Both the Poisson EZ and the negative binomial distributions suggest a heterogeneous population composed of subgroups of flagellates with different grazing rates. Although these models provide acceptable mathematical descriptions, their specific biological implications with regard to the number of flagellate subgroups remain to be proven. Based on fit of the distribution of ingested prey to a Poisson EZ, a rapid cytometnc method for estimation of grazing rates on FLB is presented. The method uses changes in the probability of grazers not ingesting FLB during short incubations (ca 15 rnin) to estimate the Poisson parameter and the fraction of extra zeros, from which the average grazing rate is calculated. Grazing rates determined by microscopy and by this cytometry method were similar. Frequency distributions of cytometric histograms of fluorescent microspheres in grazers suggest that both the Poisson EZ and negative binomial models are simplifications of a more complex distribution of grazing rates.

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Section: Discussionmentioning

confidence: 55%

Section: Discussionmentioning

confidence: 55%

Section: Discussionmentioning

confidence: 99%

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

Bratvold¹,

Srienc

Taub³

2000

Aquat. Microb. Ecol.

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“…It can be concluded, therefore, that capture of particles from the suspension, rather than some subsequent processing step such as food vacuole formation, is the rate-limiting step for feeding on such suspensions. 22 The procedure described here showed that variability of clearance rates within a cell population is significant and it depends on the physiological state of the population. The measurements also suggested that the size-class-average clearance rates of Tetrahymena are correlated with cell size, but only for the smaller cells in the population.…”

Section: Discussionmentioning

confidence: 99%

“…This is not so for feeding on concentrated suspensions, where the clearance rate is a decreasing function of the particle concentration. 22 Fitting the above equation to a time series of estimates of the fractions p i ( t ) can provide an estimate of the maximum clearance rate of the cells.…”

Section: Modeling Frameworkmentioning

confidence: 99%

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

Sweeney

Srienc

Fredrickson

1993

Biotech & Bioengineering

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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.

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Feeding heterogeneity in ciliate populations: Effects of culture age and nutritional state

Srienc¹,

Fredrickson²

1994

Biotech & Bioengineering

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We have used a novel approach in conjunction with flow cytometry to quantify the biological heterogeneity of populations of the ciliate Tetrahymena pyriformis. It was found that the rate of particle uptake of exponentially growing cells is not uniform among cells and partially correlated with cell size. The physiological state and growth history of the culture was found to affect to a large degree the population's feeding heterogeneity. Stationary phase populations exhibited more uniform feeding behavior, as cell aging affects all cells and effectively reduces their ability to feed. Cells that were removed from the growth medium and resuspended in nonnutritive medium exhibited a more heterogeneous feeding behavior. The starved cells were stimulated to feed at considerably higher rates, and the stimulatory effect was more pronounced for larger cells. It is therefore demonstrated that population heterogeneity has to be evaluated in conjunction with the populations growth state as it is determined by the history of the population's growth and nutritional state. (c) 1994 John Wiley & Sons, Inc.

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A discrete, stochastic model for microbial filter feeding: a model for feeding of ciliated protists on spatially uniform, nondepletable suspensions

Cited by 8 publications

References 42 publications

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

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

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

Feeding heterogeneity in ciliate populations: Effects of culture age and nutritional state

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