Comparative Biology of Prokaryotic Resting Cells

Abstract

Publisher Summary This chapter examines the comparison of the properties of various types of resting cells formed by prokaryotes. It also describes the formation of the resting stage, the resting cell, and the germination. The chapter largely emphasizes on the comparative aspects of resting cells. Resting cells refer to those cells in which division does not occur, endogenous respiration is absent or much decreased, and in which formation of the resting stage is part of the natural life-cycle of the organism. The resting cell is usually morphologically distinct from the growing or vegetative form, and most types are more resistant than vegetative cells to adverse conditions. Endospores of the various genera—Bacillus, Clostridium, Sporosarcina, and Thermoactinomyces—are fundamentally different from other types of resting cells. They are largely formed within vegetative cells, none of the cell wall being derived from the wall of the mother cell. They also contain unusually large amounts of Ca2+ and DPA, which can be involved in the maintenance of heat resistance and dormancy. The phenomenon of activation, sometimes a necessary prelude to germination, is observed only for endospores. Increased resistance properties, a dissemination apparatus, and timing devices are the most likely biological functions of prokaryotic resting cells, each type of resting cell is necessarily suited to one or more of these functions.