Optimal growth temperature
. Psychrophilic bacteria . Mesophilic bacteria . Thermophilic bacteria
.15-20 o c; grow best at low T0 range .30-370c; grow best at middle T0 range .50-60oc; grow best at high T0 range
NB: Most human pathogens and many of the normal flora of human bodies have an optimal temperature of 370c; There fore they are mesophilic bacteria.
3. Oxygen Base on oxygen requirements and tolerance, bacteria are divided classified as: . Obligate aerobes . Obligate anaerobes . Facultative anaerobes . Microaerophiles
Obligate aerobic bacteria grow only when free oxygen is
available to support their respiratory metabolism. They obtain ATP by using oxygen as a final electron acceptor in respiration.
Obligate anaerobic bacteria grow in the absence of oxygen; exposure to oxygen kills anaerobes. Facultative anaerobic bacteria grow in the presence or absence of oxygen. obtain ATP by fermentation or anaerobic respiration