culturing microorganisms

• What can you grow in the lab to test the effectiveness of antibiotics?

  Microorganisms
• What is a culture medium?

  A substance containing nutrients needed for microorganisms to grow
• What are two types of culture mediums mentioned?

  Nutrient broth and agar jelly
• How do bacteria appear when grown on agar plates?

  They form visible colonies or spread out evenly
• What is the purpose of an inoculating loop?

  To transfer microorganisms to the culture medium
• Why are cultures of microorganisms not kept above 25 °C in school labs?

  To prevent the growth of harmful pathogens
• How do industrial conditions differ in culturing microorganisms?

  They incubate cultures at higher temperatures for faster growth
• What is the first step in testing the action of antibiotics on bacterial cultures?

  Place paper discs soaked in antibiotics on an agar plate
• What happens to antibiotic-resistant bacteria when exposed to antibiotics?

  They continue to grow around the antibiotic discs
• What is an inhibition zone?

  A clear area where bacteria have died around antibiotic discs
• Why is a control disc used in antibiotic testing?

  To ensure any growth difference is due to the antibiotic
• How long should the agar plate be left for after applying antibiotics?

  48 hours
• What indicates a more effective antibiotic in the experiment?

  A larger inhibition zone around the antibiotic disc
• What steps should be taken to avoid contamination in cultures?

  • Sterilize Petri dishes and culture medium before use
  • Sterilize the inoculating loop by passing it through a flame
  • Lightly tape the lid of the Petri dish after transferring bacteria
  • Store the Petri dish upside down to prevent condensation
• Why is it important to sterilize the inoculating loop?

  To kill any unwanted microorganisms before transferring bacteria
• What temperature should Petri dishes be stored at to avoid contamination?

  They should be stored upside down
• What is the purpose of sterilizing the culture medium?

  To kill any unwanted microorganisms that may contaminate the culture
• What is the role of agar jelly in culturing bacteria?

  It serves as a solid medium for bacteria to grow on
• What should be done to prevent microorganisms from the air getting into the Petri dish?

  The lid should be lightly taped on
• How does the temperature affect the growth of microorganisms in different settings?

  Higher temperatures in industrial settings promote faster growth
• What is the purpose of culturing microorganisms in this practical?

  To compare the effectiveness of different antibiotics on bacteria
• How can the effectiveness of antibiotics be assessed?

  By looking at the relative sizes of the inhibition zones
• What does a larger inhibition zone indicate about an antibiotic?

  It is more effective against the bacteria
• What is the method to calculate the size of the inhibition zones?

  Measure the diameter and calculate the area using the formula
• What is the formula for the area of a circle?

  Area = πr²
• What does 'r' represent in the area formula?

  It is the radius of the inhibition zone
• How do you find the radius from the diameter?

  Divide the diameter by two
• If the diameter of an inhibition zone is 14 mm, what is the radius?

  7 mm
• If the radius of an inhibition zone is 7 mm, what is the area?

  $154 \text{ mm}^2$
• If the diameter of another inhibition zone is 20 mm, what is its radius?

  10 mm
• What is the area of an inhibition zone with a radius of 10 mm?

  $314 \text{ mm}^2$
• How do you compare the effectiveness of antibiotics using inhibition zones?

  • Measure the diameter of the inhibition zones
  • Calculate the radius by dividing the diameter by two
  • Use the formula Area = πr² to find the area
  • Compare the areas of the inhibition zones
• What conclusion can be drawn if the area of antibiotic B's inhibition zone is roughly twice that of antibiotic A's?

  Antibiotic B is more effective than antibiotic A
• How can the area of a bacterial colony be calculated?

  By measuring the diameter and using the area formula
• What units are commonly used to express the area of inhibition zones?

  cm² or mm²
• What is the significance of using π in the area calculation?

  It is a constant used to calculate the area of a circle
• What value can be used for π if a calculator is not available?

  1. 14
• What steps are involved in calculating the area of an inhibition zone?

  1. Measure the diameter of the inhibition zone
  2. Divide the diameter by two to find the radius
  3. Use the formula Area = πr²
  4. Calculate the area and compare with others