Most pathogens, however, like warmth and are known as mesophiles . They start to multiply more rapidly as the temperature rises. However, in order to destroy bacteria, temperatures must rise further. After 6 hours, in ideal conditions, one bacterial cell could become 131,072 bacteria. The acidity or alkalinity of foods will affect bacterial growth.
Pathogens vary in their oxygen requirements.
Those which require oxygen are called aerobes, e.g. Bacillus cereus . Those which do not need oxygen are called anaerobes, e.g. Clostridium perfringens and Clostridium botulinum . Those which will grow or survive with or without oxygen are known as facultative anaerobes and include Salmonella species and Staphylococcus aureus . Where there are a number of different bacteria present in food, they compete for the same nutrients. Pathogens are often not as competitive as spoilage bacteria and unless present in high numbers, will usually die.