Bacteria multiply through binary fission. This process involves the division of a single cell into two identical daughter cells, and it starts when the DNA of a bacterium divides into two replicates. The bacterial cell splits into two daughter cells that have identical DNA to the parent cell.
The daughter cells are clones of the parent cell. Generation time starts from cell formation until cell division. This is the time it takes for the cell count to double in number.
Bacterial growth includes the lag phase, log phase, stationary phase and death phase. It is affected by temperature, availability of nutrients, oxygen supply, water supply and medium acidity. The optimum temperature for the multiplication of bacteria lies between the temperature at which protoplasm coagulates and the freezing point of water. They need nutrients to grow, and they normally require organic matter. They also cannot reproduce without water. Many bacteria cannot tolerate dry conditions, but others can survive for months or years. Aerobic bacteria need oxygen for growth, whereas anaerobic bacteria find it toxic. Most bacteria thrive in an environment with a pH of around 7, which is a neutral pH.
Some bacteria, such as Escherichia coil, are capable of dividing every 20 minutes in favorable conditions. When nutrients are available and the temperature is ideal, one bacterium can generate 2,097,152 bacteria in just seven hours. After another hour, bacteria can increase to 16,777,216. This is the reason why humans quickly get sick when pathogenic microbes invade the body.