Dormancy
Dormancy is a period in an organism's life cycle when growth, development, and (in animals) physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be closely associated with environmental conditions. Organisms can synchronize entry to a dormant phase with their environment through predictive or consequential means. Predictive dormancy occurs when an organism enters a dormant phase before the onset of adverse conditions. For example, photoperiod and decreasing temperature are used by many plants to predict the onset of winter. Consequential dormancy occurs when organisms enter a dormant phase after adverse conditions have arisen. This is commonly found in areas with an unpredictable climate. While very sudden changes in conditions may lead to a high mortality rate among animals relying on consequential dormancy, its use can be advantageous, as organisms remain active longer and are therefore able to make greater use of available resources.
Annual life cycle of sympodially growing orchids with dormancy after completion of new growth/pseudobulb, e.g., Miltonia, or Odontoglossum
Annual life cycle of sympodially growing orchids with dormancy after blooming, e.g., Cycnoches ventricosum, Dendrobium nobile, or Laelia
Bacteria[edit]
Many bacteria can survive adverse conditions such as temperature, desiccation, and antibiotics by forming endospores, cysts, or general states of reduced metabolic activity lacking specialized cellular structures.[15] Up to 80% of the bacteria in samples from the wild appear to be metabolically inactive[16]—many of which can be resuscitated.[17] Such dormancy is responsible for the high diversity levels of most natural ecosystems.[18]
Bacteria enter a state of reduced metabolic activity not only during stress, but also when a bacterial population has reached a stable state.[19] Many bacteria are capable of producing proteins called hibernation factors which can bind to and inactivate their ribosomes, pausing protein production, which can take more than 50% of a cell's energy usage.[20]
A recent study[21] has characterized the bacterial cytoplasm as a glass forming fluid approaching the liquid-glass transition, such that large cytoplasmic components require the aid of metabolic activity to fluidize the surrounding cytoplasm, allowing them to move through a viscous, glass-like cytoplasm. During dormancy, when such metabolic activities are put on hold, the cytoplasm behaves like a solid glass, 'freezing' subcellular structures in place and perhaps protecting them, while allowing small molecules like metabolites to move freely through the cell, which may be helpful in cells transitioning out of dormancy.[21]