Lecture 9 - Biology 207 Lecture nine Monday, 22 Sep 2008...

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Biology 207 Lecture nine Monday, 22 Sep 2008 Bacterial growth and environmental effects binary fission and measuring growth, temperature, pH, osmotic pressure, oxygen Typical reproduction (growth) of a bacterial cell.  See  Fig. 6.1 grow means REPRODUCE increase amount of cellular constituets, elongate, divide growth means growth of the popluation/culture it is very important for studying organisms in the lab most moroorganisms will not grow on laboratory media Use a logarithmic scale to plot growth of a culture over time. Example:   Fig. 6.8, Fig. 1 Ch. 6 Sidebar reproduce every 30 mins  1 cell becomes 2 becomes 4 becomes 8 = EXPONENTIAL INCREASE potential for growth is tremendous, we would be COVERED in bacteria in minutes if not for environmental limits - consumption and waste  products logarithmic plot makes it convienent to graph and estimate growth rate of culture How is growth measured?  direct counts -- microscopy, counting cells (see book)  examin culture undermicroscope plate counts -- each cell produces a colony (see book) spectrophotometer -- measure turbidity –  Fig. 6.17   standard procedure, tells u basic information. basic principal: light source, filter that blocks out all light except one wavelenghth.  choose a wave length that passes effectively through medium but scatters when it hits bacteria. the light that passes through is detected by  photocells in the spectrophotometer. the log of the ratio of these can estimate the general turbidity of the meadium. we then relate turbidity  back to the original medium itself.  What are the phases of growth in batch  (closed)  culture (flask or test tube) –  Fig. 6.10 lag phase -- physiological adjustment to the new growth conditions  getting ready to use medium exponential phase -- balanced growth, all cellular constituents are being made at the same rate and new cells are being produced at a 
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Lecture 9 - Biology 207 Lecture nine Monday, 22 Sep 2008...

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