Question

Identify three environmental influences on microbial growth. How does each affect microbial distribution

Answer 1

The following environmental factors influence microbial growth:

1). Temperature

Metabolic reactions are carried out by enzymes that are protein in nature. Proteins are susceptible to temperature changes. Enzymes work at an optimum temperature. An increase in temperature would cause the inactivation of these proteins and thus make them inactive and inhibit the microbial growth. Organisms are also categorised into three categories based on their tolerability to temperature. These are:

a). Thermophiles/ Hyperthermophiles: can tolerate relatively higher temperature

b). mesophiles: can tolerate moderate temperatures

c). psychrophiles: can tolerate cold temperatures

2).PH

Each microbe requires an optimum PH for its growth. Based on PH toleberality, microbes can be classified as:

a).Acidophiles: Survive in acidic PH

b). Neutrophils: Survive in neutral PH

c). Alkalophiles: survive in alkaline PH

It has been observed that most pathogenic bacteria grow best in pH 7.2-7.4.

3).Oxygen

Based on oxygen requirements, microbes can be classified into 4 categories:

a).Aerobes: Need oxygen for their growth. e.g. Mycobacterium tuberculosis

b).Facultative anaerobes: These can grow under both aerobic and anaerobic conditions. Bacteria are generally facultative anaerobes. e.g. Enterobacteriaceae

c). Anaerobes. They do not require oxygen for their growth. In fact, they only grow in absence of oxygen. e.g. Clostridium

d). Microaerophiles: They generally in presence of oxygen but require oxygen less than that is present in the air. e.g.Campylobacter.