- Proper aseptic technique is crucial to ensuring growth of pure bacterial colon

Question

- Proper aseptic technique is crucial to ensuring growth of pure bacterial colonies. What is one experimental way you can test your practices to confirm that you are using proper aseptic technique? (5 points)

- In a laboratory setting, what are three ways you can properly sterilize culturing equipment? (5 points)

- For each inoculation tool, give one scenario in which use of that tool would be appropriate. (5 points)

- Do some research and describe two or three scenarios in which it would be preferable to use a stab tube vs. a growth plate. (Hint: What do bacteria use to help them move? Can motility be used to help identify many medically important pathogenic bacteria such as the Enterobacteriaceae?)

Explanation / Answer

-The purity of bacteria can be assessed by subculturing many times to observe the colony morphology under standardised culture conditions followed by microscopic examination of the bacterial cell for their distinct morphological features and grams staining.

- sterilisation in microbiology laboratories generally carried by 3 methods

1) Dry heat sterilisation: glassware, forceps and other heat resistant lab equipment can be sterilised in the hot air oven.

2) Sterilisation by moist heat: Autoclaving at the 121-degree temperature and 15lb pressure for 15 min is useful for hydrated products like media, water etc. glassware also be sterilised by this.

Filter sterilisation: the heat labile components like antibiotics, hormones and vitamines in the media are filtered through different micron size filters which filter out contaminants.

-inoculation loop: for picking a single colony from spread plate from a number of bacterial colonies it is useful.

it is also generally used to pick the colony from solid pure culture to transfer onto new culture media sub subculturing.

Micrpippet: it is helpful to inoculate from liquid culture of bacteria/ serially diluted samples to the solid plate or even onto liquid culture.

forceps: generally used to inoculate large inoculum like plant tissues for culturing.

---Stab tube: it is used to maintain cultures so that the contamination possibility is lesser than the plate cultures. stab cultures are also helpful in shipping of microbial culture than plate cultures which need more protection. In motility assay stab cultures show more advantage as the inoculum punctured in one place is mobilised leaving with mark behind so that easily observed by naked eye. But with plate cultures, it is difficult to give visual evidence for bacterial mobility.

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