Culturing Microorganisms
Biology: AQA GCSE Higher, topic 1.1.27
Growing Microorganisms
Cultures of microorganisms (microorganisms grown in a lab) can be used to investigate the effects of antibiotics and disinfectants, which both kill bacteria. Microorganisms can be grown in two mediums (materials) that contain everything that bacteria need to survive.
Agar gel plate
- Microorganisms can be grown as colonies on an agar gel plate.
Nutrient broth
- Microorganisms can be grown within a solution of a nutrient broth.
- This contains carbohydrates as an energy source, minerals and sometimes other chemicals.
Test yourself on Culturing Microorganisms
A scientist places a paper disc soaked in an antibiotic onto a bacterial culture on an agar plate. After incubation, this disc has a much larger clear area around it than the other discs. What does this show?
Why can individual bacterial colonies be seen on an agar plate but not in a nutrient broth culture?
A nutrient broth is prepared without any carbohydrates before bacteria are added. What effect would this most likely have on the bacteria?
Why do scientists grow bacteria on an agar plate rather than in a nutrient broth when they want to measure the area an antibiotic clears?
A student tests antibiotic A and antibiotic B on bacterial cultures grown on agar plates. Antibiotic A clears a much bigger area than antibiotic B. What can the student conclude?