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Growth Of Microorganisms


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Growth Of Microorganisms

  1. 1. Growth of Microorganisms The Growth Curve
  2. 2. The Growth Curve
  3. 3. The Growth Curve
  4. 4. The Growth Curve <ul><li>A plot of log10 (number of organisms) against time for a growing culture results in a predictable pattern. </li></ul><ul><li>The log value is used as it is easier to plot onto a graph. </li></ul>
  5. 5. The Growth Curve <ul><li>Lag phase </li></ul><ul><li>Short period immediately after inoculation </li></ul><ul><li>Organisms are synthesising the enzymes needed to exploit the new medium. </li></ul><ul><li>Cells may grow in size but not usually in number </li></ul><ul><li>(If organisms have been transferred from an identical medium, at the same temperature, the lag phase may be very short). </li></ul>
  6. 6. The Growth Curve <ul><li>Exponential phase (log phase) </li></ul><ul><li>Organisms have started to reproduce </li></ul><ul><li>Abundant food, absence of competition and of inhibiting factors such as toxic waste products allows cell division to occur at a high rate. </li></ul><ul><li>The population doubles at regular intervals. </li></ul>
  7. 7. The Growth Curve <ul><li>Plotted as arithmetic numbers of cells, the log phase would be a curve of ever increasing gradient; plotted as log10 of cell numbers, it gives a straight line . </li></ul>
  8. 8. The Growth Curve <ul><li>Stationary phase </li></ul><ul><li>In a closed culture food soon runs out or the organisms become poisoned by their own accumulated wastes </li></ul><ul><li>As a results growth slows down and stops. </li></ul><ul><li>If the population is being measured by a total cell count, or by turbidity readings, there may be no apparent further change. </li></ul>
  9. 9. The Growth Curve <ul><li>Death phase </li></ul><ul><li>A viable count will soon show a decline in cell numbers as cells die </li></ul><ul><li>This will continue until there are no living cells left.. </li></ul>