Practical 2: Septic method for entering culture tubes and transferring microorganisms

What type of microorganisms would you expect to grow on TSA (Tryptic Soy Agar)?

TSA supports many types of bacteria, including both good and bad types.

What type of microorganisms would you expect to grow on SD (Sabouraud Dextrose Agar)?

SD is designed for growing fungi, like yeasts and molds.

What is pure culture

A pure culture contains only one type of species of microorganism, with all cells being genetically identical, allowing for study of its characteristics.

What is contamination?

Contamination is when microbes are present which means it isn’t sterile and will grow microbes that can interfere with experimental results or the purity of cultures.

Explain the importance of sterilisation when trying to obtain a pure culture

Sterilisation is the destruction or removal of all forms of microbes. This is important to avoid cross contamination to achieve best results and ensure that only the desired microorganism is cultivated.

What is meant by the term 'Aseptic Technique'?

Aseptic Technique is a way of working that keeps harmful germs away from what you are doing. This maintains only pure culture. This technique is used in labs and hospitals to prevent infection during medical procedures and experiments

Describe how to sterilise an inoculation loop

To sterilise an inoculation loop, it should be heated into the hottest flame which is the inner blue flame until it glows red hot and then allowed to cool before use. Make sure it is held into 60 degree angle and held like a pencil.

Why is it important to flame the lip of the culture tube during an aseptic transfer?

Flaming the lip of the culture tube helps to kill any harmful germs that could be on the rim. This prevents air from getting trapped inside the test tube, which can carry germs into the culture, keeping the environment clean for the experiment.

Why is the culture vortexed after inoculation?

The culture is vortexed, or mixed, to evenly spread out the microbes. This helps to ensure that all parts of the sample are similar and that the microbes can grow well.

What is the purpose of the streak plate method?

The streak plate method is used to isolate and obtain pure cultures of microorganisms by spreading a diluted sample across the surface of an agar plate to obtain individual colonies.

What is a bacterial colony?

A bacterial colony is made from millions of individual bacterial cells that can be seen with a true naked eye

Explain why the loop must be sterilised between each streak?

The loop must be sterilised between each streak to remove any remaining bacteria from the previous streak, preventing contamination and allowing for the isolation of discrete colonies.

Where on the streak plate would you expect to find single colonies?

You would expect to find single colonies on the edge of the streak line where the agar is less crowded. This is where there is more space for the bacteria to grow without too many others around