Certain unicellular organisms can form resting cells called acinetes with thick walls and nutrient stores to survive harsh conditions. When conditions improve, the acinete explodes and releases new cells. Acinetes are specific to filamentous cyanobacteria and form due to environmental stress. They have a thick outer wall and store genetic material and nutrients. When conditions improve, the new cells emerge and grow normally.
Certain types of unicellular organisms can change cell structure under harsh conditions such as nutrient scarcity in the environment. These resting cells, which neither grow nor consume much energy for biological functions, have evolved to survive unfavorable growth conditions. An acinete is a type of cell at rest, with a characteristically thick wall and a storehouse of nutrients within. When favorable conditions develop in the environment around the acinete, this resting cell explodes and releases more new cells, which begin to grow normally.
The Greek word for motion is kinetos; commonly, the letter “a” is placed before a Greek word to mean the opposite of what the word means. An acinete, therefore, refers to an object that does not move. The term is specific to a certain subgroup of bacteria called filamentous cyanobacteria, so called because they tend to grow in long filaments. Many other bacteria develop resting cells in stressful environments, but these are more commonly called spores rather than acinetes, as their characteristics tend to be different.
Cyanobacteria, like all bacteria, require food and appropriate environmental conditions to live and reproduce. Environmental stresses can kill bacteria altogether or cause active cells to enter an akinetic resting state. Examples of pressures that can cause bacteria to change states include a lack of ambient nitrogen, a change in the wavelength of light, or having too many other cells competing for the same resources.
Typically, in a microbial population, once individual cells have grown to occupy the available space and eat the available nutrients, environmental stress develops. Generally, in a population of cyanobacteria, acinetes will develop at this time, and not when the population still has space and nutrients to grow. In an aqueous environment, for example, a high population of cyanobacteria can make the water cloudy. This cloudiness blocks certain wavelengths of light, and cells can recognize these changes, which can push microbes into a resting state.
Characteristics of an acinete include a very thick outer wall and a storehouse of nutrients and genetic material within. Due to storage requirements, the acinete is also larger than the normal living cell. The interior of the cell opens when the cell senses the return of suitable conditions and the newly reproduced cells emerge in an arrangement of filaments. If these new cells can populate the new environment, such as a pond that has been filled with fresh meltwater, then they can grow and reproduce to the point where the same cycle must repeat itself.
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