Novel features of computer-simulated clonal life of Paramecium caudatum.

The clone of the ciliated protozoan Paramecium caudatum has the immaturity period of about 60 fissions and the lifespan of about 600 fissions. These life cycle figures have been depicted through laboratory experiments that allow continuous cell divisions for hundreds, which never occur in nature. We here constructed the nature-mimicking model culture that alternated the log- and stationary phases to allow conjugation, and computer-simulated the age structure modifying parameters such as cell distributions to start the culture, fission rates, death rates, immaturity periods, probabilities of conjugation, proportions of transplantation and so on.

Abrupt increase in UV sensitivity at late log-phase of growth in Paramecium tetraurelia.

In this study, changes in UV sensitivity, a parameter of the clonal aging that has been studied in the daily reisolation culture, were examined in the logarithmically growing Paramecium culture. Cells in logarithmically growing cultures are thought to change the internal states under rapidly changing external conditions. In contrast, cells in daily reisolation cultures gradually change the internal states, the process being called clonal development and aging, under the external conditions that are kept almost constant.

A new mutation in the timing of autogamy in Paramecium tetraurelia.

We have isolated a new type of Paramecium tetraurelia mutant, named rie-2, that has a long immaturity period until autogamy. We previously isolated such an autogamy mutant, designated rie-1. These two mutants had some additional common features such as dependence of the occurrence of autogamy on the temperature, involvement of a single recessive gene, lower fission rate and shorter clonal life span.

A Paramecium tetraurelia mutant that has long autogamy immaturity period and short clonal life span.

We have isolated an unprecedented mutant of Paramecium tetraurelia that has a long immaturity period until autogamy. This mutant stock, d4-RK, screened for 0% autogamy at the age of 27 fissions, began to undergo autogamy around the age of 50 fissions in some clones and underwent autogamy scarcely even after the age of 100 fissions in others. d4-RK expressed its mutant phenotype at 25 degrees C, but resembled the wild-type phenotype at 32 degrees C.

Catalase is the bacteria-derived detoxifying substance against paramecia-killing toxin in wheat grass powder infusion.

Paramecium cells are usually cultured in a wheat grass powder infusion inoculated with Klebsiella pneumoniae. However, non-bacterized wheat grass powder infusion is toxic to paramecia, and bacteria-derived substance detoxifies the toxic substance. Here, the detoxifying substance from K.