Micro-organisms and their applications

• What is the purpose of aseptic techniques in microbiology?

  To prevent contamination of the culture and the environment.
• Why must inoculating loops be sterilised before use?

  To kill any unwanted microorganisms and prevent contamination.
• How should work surfaces be prepared in aseptic technique?

  Disinfect before and after the procedure to reduce contamination.
• Why are Petri dishes only opened briefly during inoculation?

  To minimise airborne contamination.
• Why is the neck of bottles flamed during aseptic technique?

  To kill microbes at the opening and reduce contamination.
• Why are Petri dishes sealed but not completely taped?

  To prevent contamination while still allowing air exchange.
• At what temperature are school incubators typically set, and why?

  25 °C to avoid growing harmful pathogens.
• What does each bacterial colony on agar typically originate from?

  A single bacterial cell.
• How can you estimate the number of bacteria in an original sample?

  By counting colonies after serial dilution and plating.
• Why is serial dilution used before plating bacteria?

  To reduce concentration so colonies can be counted accurately.
• How does temperature affect bacterial growth?

  Higher temperatures speed up growth until enzymes denature.
• What is the optimum temperature for human bacterial pathogens?

  Around 37 °C.
• How does refrigeration affect bacterial growth in food?

  Slows down enzyme activity, reducing bacterial growth.
• What effect does freezing have on bacteria in food?

  Stops growth but does not kill all bacteria.
• Why is cooking food important in terms of bacterial control?

  High temperatures kill bacteria.
• What fungus is used to produce penicillin?

  Penicillium.
• What type of respiration does Penicillium require in fermenters?

  Aerobic respiration.
• Why is oxygen pumped into industrial fermenters?

  To supply Penicillium with oxygen for aerobic respiration.
• Why is the fermenter stirred?

  To ensure even distribution of nutrients and oxygen.
• What pH is optimal for Penicillium growth?

  Around pH 6.5.
• What is penicillin classified as in terms of fungal metabolism?

  A secondary metabolite.
• When is penicillin produced during fungal growth?

  After rapid growth phase, in the stationary phase.
• What method is used to separate fungal cells from penicillin?

  Filtration.
• How is penicillin extracted from the culture medium?

  Using solvent extraction and purification.
• How is penicillin prepared for medical use?

  By crystallisation or freeze-drying.