The growth of bacteria is affected by water, oxygen, nutrients, temperature and the medium's acidity. Bacteria are single-celled organisms found in water, air and on solid surfaces. Bacterial growth refers to the bacteria increasing in numbers of cells, rather than size.
Bacterial growth occurs in four phases: Lag phase, log phase, stationary phase and death phase. One factor affecting this growth is temperature. Bacteria can grow in many different temperatures, but different types have their own temperature preference. For example thermophilic bacteria will grow best if the temperature is greater than 104 degrees Fahrenheit. Another factor is the presence of oxygen. Aerobic bacteria need oxygen to grow, while oxygen is poisonous to anaerobic bacteria.