culturing microorganisms

what do culture mediums contain?

• carbohydrates

• minerals

• proteins

• vitamins

ways to culture bacteria:

• nutrient broth solution

• solid agar jelly

how do you make an ajar plate?

1. hot agar jelly is poured into a Petri dish

2. when the jelly is set, inoculating loops transfer microorganisms to the culture medium

   OR a sterile dropping pipette and spreader can be used to get an even bacteria covering

why are cultures of microorganisms in school not kept above 25°C?

harmful pathogens thrive at 37°C

why are cultures incubated at higher temperatures in industrial conditions?

so they can grow faster

aseptic technique:

• thoroughly wash hands

• disinfect work surfaces

• sterilise all equipment before use

• flame bottles, forceps, inoculating loops (kills any bacteria on equipment)

• don’t put down flamed equipment

• keep equipment by the Bunsen burner (kill bacteria)

• only remove petri lid when necessary and open it only slightly for minimal time (prevent unwanted bacteria in the air contaminating the plate)

• Petri dishes stored upside down to stop drops of condensation falling on the agar

how can you test the effects of antibiotics on bacterial growth?

1. place paper discs soaked in different types or different concentrations of antibiotics on an agar plate

   (the antibiotic should diffuse into the agar jelly)

2. antibiotic-resistant bacteria will continue to grow on the agar around the discs but the non-resistant strains will die and a clear inhibition zone will be left

3. leave the plate for 48 hours at 25°C

what should you ensure when testing the effects of antibiotics on bacterial growth?

a control - a paper disc that hasn’t been soaked in antibiotics but sterile water

how do you know how effective the antibiotic is against the bacteria?

larger inhibition zone = more effective