The most common way microorganisms are grown (cultured) is in a "culture medium", a combination of carbohydrates, minerals, proteins and vitamins. A nutrient broth solution or solid agar jelly can be used as the culture medium. On the surface of jelly, bacteria will form visible colonies, or they may spread out to give an even layer of bacteria.

At school, cultures of microorganisms are not kept above 25 •C since pathogenic microorganisms (microorganisms that cause disease) tend to grow faster above this temperature. Industrial conditions allow cultures to grow much faster as they are incubated at a much higher temperature.

How to grow microorganisms on an agar plate

What is an agar plate? An agar plate is a Petri dish that contains a growth medium solidified with agar, used to culture microorganisms. Sometimes selective compounds are added to influence growth, such as antibiotics.

Agar plates are made by pouring hot agar jelly into shallow round plastic dishes called Petri dishes. Microorganisms are transferred to the culture medium using inoculating loops (wire loops) after the jelly has cooled and set. An alternate method for spreading bacteria evenly is to use a sterile dropping pipette and spreader. Once the bacteria are spread, they multiply.

Growing microorganisms on an agar plate

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