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2.4 identify data sources, plan and choose equipment or resources to perform a first-hand investigation to identify microbes in food or in water
identify data sources, plan and choose equipment or resources to perform a first hand investigation to identify microbes in food or in water
- Agar is a jelly-like substance obtained from seaweed. When it is dissolved in water, nutrients suitable for microbes can be added to it before it sets to form a gel. If a microbe makes contact with the agar and if conditions are suitable, the microbe will grow and reproduce to form a visible colony.
- To design a first-hand investigation to identify microbes in food and water, firstly identify data about microbiological techniques from practical manuals or the Internet. Gather information about the techniques used to grow micro-organisms on agar plates in Petri dishes. You will need to know what sort of nutrients can be added to agar, the correct way of exposing the agar to the source of micro-organisms and the safety precautions that must be followed once a plate has been exposed. Also you will need to know the best temperature for microbial growth and how to distinguish between colonies of bacteria and fungi, growing on agar plates.
- Use the information to plan a valid and reliable investigation. You will need to decide on which nutrients you will add to the agar, what food and water samples you will test and how you will expose the agar to the microbes that may be present in your food and water samples. Decide on the temperature you will provide for microbial growth.
- Choose equipment and resources that will ensure your investigation is safe. Carry out a risk assessment of your experimental procedures and address potential hazards. In this type of investigation, the most important safety procedures are:
- to seal and not open again the Petri dishes after exposure
- to correctly autoclave exposed Petri dishes prior to final disposal.
- Perform your investigation. Dispose carefully and safely of the waste materials produced during the investigation. Safe working practices such as wearing latex gloves, washing benches and hands with chemical treatments for sterilisation are important when working with micro-organisms.
Use data from the investigation to explain why cleanliness in food, water and personal hygiene practices are important.