Growing Bacteria in a lab

• Bacteria and some other microorganisms) are ciltured in a "culture medium", which contains the carbohydrates, minerals, proteins and vitamins they need to grow
• The culture medium used can be a nutrient broth solution or solid agar jelly
• Bacteria grown on agar 'plates' will form visible colonies on the surface of the jelly, or will spread out to give an even covering of bacteria
• Making an agar plate - To make an agarplate, hot agar jelly is poured into shallow round plastic dishes called petri dishes.
• Making an agar plate - When the jelly's cooled and set, inoculating loops (wire loops) can be used to transfer microorganisms to the culture medium. Alternatively, a sterile dropping pipette and spreader can be used to get an even coating of bacteria
• Making an agar plate - after trasnferring the microorganisms on the jelly, the microorganisms multiply
• In the lab at school, cultures of microorganisms are not kept above 25°C, because harmful pathogens are more likrly to grow above this temperature
• You need to use uncontaminated cultures
• Contamination by unwanted microorganisms will affect your results and can potantially result in the growth of pathogens
• Avoiding uncontaminated cultures

  -The petri dishes and culture medium must be sterilised before use (e.g. by heating to a high temperature), to kill any unwanted microorganisms that may be lurking on them
• Avoiding uncontaminated cultures

  -If an inoculating loop is used to transfer the bacteria to the culture medium, it should be sterilised firts by passing it through a hot flame
• Avoiding uncontaminated cultures

  After transferring the bacteria, the lid of the Petri dish should be lightly tapped on - to stop microorganisms from the air getting in
• Avoiding uncontaminated cultures

  -The Petri dish should be stored upside down - to stop drops of condensation falling onto the agar surface