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A Description of the Major Steps Involved in Endospore Formation

The bacterial environment can become inhospitably lacking in nutrients if the species' favored nutrients have all been used up in the bacterial metabolism. Some types of bacteria, such as Bacillus and Clostridia can develop dormant forms called endospores when the necessary nutrients are exhausted. These endospores are tougher, smaller versions of the original bacterial cell, and can survive as dormant cells with the bare minimum of metabolic activity until the environment becomes hospitable again in terms of nutrient availability. Sensing the return of suitable nutrients, the endospore turns back into a normal bacterium and starts growing and reproducing again. Turning into an endospore only takes the bacterium about seven hours, but involves lots of distinct steps.

Stage 0 to Stage I
- The starting point of an endospore is as a regular bacterial cell. This is Stage O. The next step, Stage I, involves movement of the cell's DNA. It forms a filament and stretches out along the longest axis of the bacterium.
Stage II
- The endospore is going to be smaller than the original cell, so the original cell begins to divide into one large portion and one small portion in Stage II. The small portion will survive as the future endospore, and the larger portion is called the "mother cell."
Stage III, Stage IV and Stage V
- The mother cell swallows up the smaller cell portion in Stage III. This means that the future endospore, now called a "forespore," has its own membrane layer around it but also has the mother cell's membrane around it. In the next step, Stage IV, the future tough coating of the endospore starts being synthesized between the two membrane layers. Stage V begins when this coating starts to be laid down.
Stage VI and Stage VII
- Once the endospore coat is finished, the spore has to mature so that it can become resistant to environmental stresses such as hot temperatures, lack of water and ultraviolet light. When the spore is ready to tackle its new environment, Stage VII begins and the mother cell dies off and releases the endospore.

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