Bacteria needs water, nutrients, the right temperature range and a certain level of acidity in order to grow. Some bacteria require oxygen to grow, while for others, oxygen prevents growth.
Water is one of the most important factors in bacterial growth. Bacteria use water to dissolve food containing nutrients. Water is also essential for bacteria to process waste products.
Food is essential for bacteria to live and reproduce. Starches, sugars and other substances provide both energy and nutrients to bacteria.
The acidity of the environment surrounding bacteria can greatly affect its rate of growth. Acidity is measured using the pH scale, which runs from 0 to 14. The lower the value, the more acidic the substance is. Higher values indicate an alkaline substance. Most bacteria reproduce best at a neutral pH level, or 7 on the scale. Reproduction is usually possible with an acidity of as low as 4.5, although this depends on the type of bacteria.
The optimum temperature range for bacteria to grow also varies greatly depending on the type of bacteria. Temperatures below 45 F slow down bacterial reproduction, and temperatures above 140 F kill most types of bacteria. This is why refrigerators, freezers and ovens are essential to prevent food poisoning.