W1 quiz
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What are the defining features of microorganisms?
<1mm diameter simple organisation qbiquitous
Why are the streak plate method and aseptic technique important in identifying bacteria?
To avoid contamination To obtain a pure culture of only ONE type of organism To separate microorganisms from a mixed culture
How do the majority of bacteria grow?
By binary fission
What is the correct order for the phases of growth of a single-celled microorganism in a closed system?
Lag Log (exponential) Stationary Death
What environmental factors may affect microbial growth?
Temperature Water pH Atmosphere Light
Which methods can be used to control microbial growth?
Heat sterilisation Filtration Radiation
What is the difference between a simple and differential stain?
A simple stain provides information about the morphology of bacteria while a differential stain distinguishes between types of bacteria based on physical or chemical properties of, for example, the cell wall.
In which order should the dyes and reagents be applied to the slide of heat-fixed bacteria when Gram staining?
• Crystal Violet • Iodine • Alcohol • Safranin
What is the difference between a Gram-positive and Gram-negative cell wall?
Gram-positive cell walls are 90% peptidoglycan and do not have an outer membrane while Gram-negative cell walls are 10% peptidoglycan and do have an outer membrane.
In the Gram stain procedure, a thick smear of bacteria is problematic because:
• The smear stains unevenly • A false positive result may be obtained • Individual cells are hard to find