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culturing microorganisms in a lab


1) Using a sterile petri dish containing agar jelly
2) microorganisms are transferred to the plate from a sample(bacteria in a broth) using a sterile implement(wire inoculation loop)
3) incubate plates adding nutrients to the agar to help improve growing conditions of the microorganisms


aseptic techniques


Aseptic techniques prevents contamination of cultures by unwanted microorganisms which may affect growth of microorganisms being cultured / give imprecise results / hazardous to health / costly(industrial scale)

1) long hair tied back
2) work near bunsen burner - hot air rises + convection currents
3) regular disinfection of surfaces
4) sterilisation of instruments before + after use via bunsen burner
5) neck of broth past flame before + closing - air moves out of container
6) minimise the time which the agar plate is open + seal lid immediately - reduces chances of airborne contamination of culture + inoculation cabinet(chamber which contains sterile air)
7) sterilse all glassware before + after use on an autclave(machine whch steams equipment at high pressure)


factors affecting the growth of microorganisms


1) using sterile pipette, add same volume(o.1cm3) of sample bacteria from broth to each of 6 agar plates then discard pipettes safely after use
2) spread broth across entire surface of agar using a wire inoculation loop(sterilise)
3) put lids on agar plates + tape them shut
4) 3 plates = fridge at 4’
3 plates = incubator at 25’
incubate upside down to stop condensation forming on the lid from dropping the agar
5) negative controls = same but without bacteria
6) leave plates for 24hrs + count number of colonies formed + record results + work out mean number of colonies per temperature

pH = buffers
nutrient availability = different preparations of agar
use of spectrophotometer = turbity(cloudiness) of broth(high = more cells present = more replication taken place)