Question

How are environmental factors used to control microbal growth? Give some everyday examples.

Answer 1

Growth of micro-organisms depend upon it's surroundings.Temperature,pH,oxygen level,solute concentration etc,affect microbial growth to great extent.

Temperature-Each micro-organisms has a optimum temperature range required for growth.If temperature is very high or very low,micro-organisms won't survive.For example E.coli grows at optimum temperature of 37 degree celcius.Heating at 121 degree celcius for 15 mins in an autoclave usually kills most of the micro-organisms.

pH-pH refers to acidity or alkalinity of a solution.It is a measure of hydrogen ion activity of a solution.All bacteria function at an optimum pH range.For example E.coli functions at an optimum pH 7.It cannot survive if environment is too acidic or too alkaline

Oxygen content- Some micro-organisms require oxygen for their growth.They are termed as aerobes,others grow in absence of oxygen anaerobes.Ecoli is a aerobes which cannot survive on oxygen deficient environment.

Carbon -nitrogen source-Micro-organisms use carbon and nitrogen as energy source.They won't survive in environment deficient in carbon and nitrogen.

Solute concentration- Solute concentration of the environment should be optimum.Hypertonic and hypertonic solutions don't favour microbial growth.Ecoli cannot withstand hypertonic solutions.