Culturing Microorganisms - PRACTICAL Flashcards
Cell Biology (33 cards)
What is the purpose of a culture medium?
To grow bacteria and other microorganisms
It contains carbohydrates, minerals, proteins, and vitamins needed for growth.
What are two types of culture media mentioned?
- Nutrient broth solution
- Solid agar jelly
What do bacteria form on the surface of agar plates?
Visible colonies or an opaque covering of bacteria
What is used to transfer microorganisms to the culture medium?
- Inoculating loop
- Sterile dropping pipette
- Spreader
At what temperature are cultures of microorganisms typically kept in schools?
Above 25 °C
Why are pathogens more likely to grow above 25 °C?
Because harmful pathogens are more likely to grow at higher temperatures
What temperature conditions are used in industrial settings for culturing bacteria?
Higher temperatures to promote faster growth
What is the first step in testing the action of antibiotics on bacterial cultures?
Place paper discs soaked in different types or concentrations of antibiotics on an agar plate
What is the area called where bacteria die around the antibiotic disc?
Inhibition Zone
What is the purpose of using a control disc in antibiotic testing?
To ensure any difference in bacterial growth is due to the antibiotic alone
How long should the agar plate be left for after placing the antibiotic discs?
48 hours at 25 °C
What does a larger inhibition zone indicate?
The antibiotic is more effective against the bacteria
What can contamination by unwanted microorganisms lead to?
Affecting results and potentially causing the growth of pathogens
How should Petri dishes and culture medium be prepared to avoid contamination?
Sterilized before use, e.g., by heating to a high temperature
What should be done to the inoculating loop before transferring bacteria?
Sterilized by passing it through a hot flame
How should the lid of the Petri dish be secured after transferring bacteria?
Lightly taped on
Why should the Petri dish be stored upside down?
To prevent drops of condensation from falling onto the agar surface
What can be compared to assess the effectiveness of different antibiotics on bacteria?
The relative sizes of the inhibition zones
A larger inhibition zone indicates a more effective antibiotic against the bacteria.
What does a larger inhibition zone around a disc indicate?
More effective antibiotic against the bacteria.
To obtain accurate results, what should be calculated for the inhibition zones?
The area of the inhibition zones using their diameter.
What is the equation for the area of a circle?
Area = πr²
In the equation Area = πr², what does ‘r’ represent?
The radius of the inhibition zone.
How is the radius of the inhibition zone calculated?
It’s equal to half the diameter.
What units are used to express the area of an inhibition zone?
cm² or mm².
