Microbiology

• What is the purpose of using aseptic technique in microbiology?


  To prevent contamination of the environment and cultures by microbes.
• What are the steps involved in aseptic technique?


  1. Sterilize Petri dishes and nutrient agar before use.
  2. Sterilize the inoculating loop before and after use.
  3. Lift the Petri dish lid slightly to prevent contamination.
  4. Secure the lid with adhesive tape and label it.
  5. Incubate inoculated agar plates at 25℃ for 24-48 hours.
  6. Sterilize plates and equipment after use.
• At what temperature should inoculated agar plates be incubated in school laboratories?


  25℃
• What is the role of nitrogen in microbial growth?

  Nitrogen is necessary for amino acid synthesis.
• What is the optimum temperature range for bacterial enzymes?


  The most suitable range is 25-45℃.
• What pH do most bacteria favor for growth?


  pH 7-8, which is slightly alkaline.
• What are the classifications of bacteria based on oxygen requirements?

  • Obligate aerobe: Requires oxygen to reproduce.
  • Facultative anaerobe: Thrives in oxygen but can respire anaerobically.
  • Obligate anaerobe: Cannot reproduce in the presence of oxygen.
• What is the purpose of the Gram stain method?


  To classify bacteria as Gram positive or Gram negative.
• What are the steps in the Gram staining process?


  1. Smear a glass slide with the bacterial sample and heat to fix.
  2. Stain with crystal violet.
  3. Treat with iodine to fix the stain.
  4. Decolorize with alcohol.
  5. Counterstain with safranin.
• What color do Gram positive bacteria appear after staining?


  Purple
• What color do Gram negative bacteria appear after staining?


  Red
• What is the structural difference between Gram positive and Gram negative bacteria?


  • Gram positive: Thick peptidoglycan layer retains crystal violet stain.
  • Gram negative: Thin peptidoglycan layer with a lipopolysaccharide layer that does not retain crystal violet.
• Why are Gram negative bacteria more difficult to control in medical settings?


  They have a lipopolysaccharide layer that provides protection from antibiotics.
• What are the three main shapes of bacteria?

  • Cocci: Spherical
  • Bacilli: Rod-shaped
  • Spirilla: Spiral or corkscrew-shaped
• How can bacteria be distinguished from each other?


  • By shape
  • Staining characteristics
  • Metabolic features
  • Antigenic features
  • Genetic features
• What is the definition of media in microbiology?


  • Media: A gel or liquid containing nutrients used to grow bacteria or microorganisms.
• What is the primary carbon and energy source for microbial growth?

  Glucose
• What additional growth factors can be added to microbial cultures?


  Water, vitamins, and mineral salts.
• What is the purpose of ensuring population size in microbiology?


  To determine the number of microorganisms present.
• What does the term "colony" refer to in microbiology?


  A colony is composed of two or more organisms living in close association with, or connected to, one another
• How is the population size calculated in microbiology?


  Population size = number of colonies x dilution factor.
• Why is it important to use aseptic technique in microbiology?


  To prevent contamination of the environment and cultures by unwanted microbes.
• What are the steps to ensure aseptic technique when handling cultures?


  • Sterilize Petri dishes and nutrient agar before use.
  • Use a sterilized inoculating loop for transferring bacteria.
  • Flame the loop before and after use.
  • Slightly open the Petri dish lid to prevent contamination.
  • Secure the lid with adhesive tape after inoculation.
• What is the limitation of using a colorimeter in counting microorganisms?


  A colorimeter cannot distinguish between dead and live cells.
• What is the role of dilution in microbiological counting?


  Dilution decreases the concentration of cells to make counting easier.
• What happens to the colony count after plating a sample?


  Each colony represents a single cell from the original sample.
• What should be done to the Petri dish after inoculation?


  The lid should be secured in place with adhesive tape and labeled.
• Why is it necessary to sterilize the inoculating loop?


  To prevent contamination of the cultures being handled.
• What is the function of the Bunsen burner in microbiology?


  It is used to sterilize the inoculating loop.
• What is the significance of measuring cloudiness in a liquid sample?

  It indicates the number of microorganisms present in the sample.
• How does the dilution factor affect the calculation of population size?


  The dilution factor is multiplied by the colony count to determine population size.