A formal mortality analysis for populations of unicellular organisms (Saccharomyces cerevisiae)

A theoretical analysis of the reproductive capacity of yeast (Saccharomyces cerevisiae) under different experimental settings reveals interesting patterns and inter-experimental relations of mortality in yeast. The data on yeast lifespan were derived from experimental research by Meisel (Untersuchungen ueber die Korrelation von Abtoetung und Lebensspannenverkuerzung durch mutagene Agentien bei Hefezellen (Thesis) Cologne, 1984). The analysis is based on the formulation of a "weak senescence principle". From this the structure of age-specific mortality is defined and employed as the functional constituent of three hierarchical types of mortality models. Model A consists of one such constituent, model B includes many of these, and in model C mortality is given a phase structure in addition. The models incorporate a few basic hypotheses on "damage" and "ageing", on partitions into subpopulations, and on mortality "shifts", according to the particular experimental treatment. It is shown that the theoretical distributions derived from these models and hypotheses yield extremely good fits to the experimental data.