Bacterial and diesease

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  • Created by: Hazel99
  • Created on: 22-09-16 17:43
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  • Measuring the growth of bacterial cultures
    • Haemocytometer
      • Specialised thick microscope slide with a rectangle chamber that holds a standard volume of liquid.
        • 0.1mm3
    • the sample of nutrient broth is diluted by half with an equal volume of tryan blue
      • A dye that stains dead cells
        • So you can identify the living cells
      • measurements at regular time intervals throughout the life of a bacterial colony.
      • 16 squares is usually counted and the mean calculated
    • Optical methods
      • Measuring the number of cells in a culture is by Turbidimetry
      • A specialised form of colorimetry
      • As the number of bacterial cells in a culture increase it becomes increasingly cloudy looking or turbid
      • Turbid = absorbs more light
      • Colorimeter measures how much light passes through
      • A relationship between the turbity of the culture and the number of bacterial cells present.
    • Dilution plating
      • Total viable cell count
      • Not possible to workout individual colonies
        • Problem solved by diluting  the original culture in stages until a point is reached the colonies can be counted.
      • Two or more plates where individual colonies can reach a mean.
        • Accuracy = checked using a haemocytometer
    • Area and mass of fungi
      • Measure diameter of the patches of mycelium
      • Compare growth rates in different conditions
      • Can find optimum temperature to grow.
      • Test the dry mass of the Microorganism
        • Best done in liquid broth removed at regular intervals and separated in a centrifugation or filtering
          • Material dried so no more mass is lost.
            • The conditions which produce the greatest dry mass of fungus are the optimum ones for growth.


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