Microbes, alternatively known as microorganisms, are essential to humans for processes such as digestion, waste excretion and nutrient absorption.
Some primary examples are bacteria (e.g amoeba) and fungi (e.g yeast)
Bacteria Growth
Bacteria require suitable temperature, pH and nutrients provisions to grow (oxygen and water)
Temperature and pH - enzymes in bacteria can denature.
Oxygen and water are needed for growth.
However, growth is limited as resources (nutrients) are limited, or the bacteria growth can no longer be supported by the environment (too small environment, too much waste etc.)
Inhibiting Bacteria Growth
Hygienic practises such as sanitisation (disinfectant) and personal hygiene (washing hands, antiseptics), cleaning equipment, and appropriate food storage (refrigeration, use-by dates) as well as avoiding cross-contamination prevent food spoilage via microbes.
The Importance of Microorganisms
Microorganisms release enzymes that enable sugar digestion, and can also inhibit pathogenic bacteria - they are quite common in the digestive system.
Recombinant DNA technology:: AKA genetic modification. Uses plasmids from bacteria as they are cheap, easy to obtain and rapidly growing in order to produce things such as human insulin.
Requires the identification of a suitable plasmid from a bacteria using a restriction enzyme.
Then, needs a specific gene that is to be replicated (from another cell) to be isolated. The same restriction enzyme is used to cut this.
Ligase enzyme is used to replace the gene from the other cell in the bacteria, and the plasmid is returned to the original bacteria.