Lecture 2.10

Lecture 2.10 - GROWTH OF BACTERIAL POPULATIONS GROWTH OF...

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Unformatted text preview: GROWTH OF BACTERIAL POPULATIONS GROWTH OF BACTERIAL POPULATIONS Bacteria usually exist in complex communities in nature Communities associated with surfaces where nutrients are more plentiful (biofilms) Pure cultures grown in lab are usually propagated as liquid cultures in appropriate growth medium (empirically formulated) Convenient but not entirely authentic Figure 23-0 Figure 23-5 Figure 23-6 Attachment (adhesion of a few cells to a suitable solid surface) Development (more growth and polysaccharide) Colonization (intercellular communication, growth and polysaccharide formation) Cell Polysaccharide Surface Water channels Figure 23-7 Fig. 6-10 Gr owth phases Lag Exponential Stationar y Death Tur bidity (optical density) Viable count Time 10 9 8 7 6 Log 10 viable organisms/ml 1.0 0.75 0.50 0.25 0.1 Optical density (OD) Fig. 6-8 10 3 10 2 10 1 1 2 3 4 5 Time (h) 100 500 1000 Number of cells (arithmetic scale) Number of cells (logarithmic scale) Logar ithmic Ar ithmetic Exponential Growth Fig. 6-9 Time (h) 1 10 7 1 2 3 5 Population doubles in 2 h 3 10 7 2 10 7 4 10 7 6 10 7 8 10 7 1 10 7 4 1 2 3 6 4 5 t = 2 n = 1 g = = 2 h t n Slope = 0.15 Cells/ml 4 10 7 2 10 7 Cells/ml t = 6 h n = 1 g = = 6 h t n Population doubles in 6 h 2 h Slope = 0.05 lope of semilog plot= specific gr owth r ate Specific Gr owth Rate : k = 0.301 n/ t, where n= # of doublings, and, t = time ) log (log 3 . 3 301 . log log 2 log log log 2 log log log 2 N N N N n n N N n N N N N n- =- = =- + = = uestion: How did the authors of the book calculate that a single bacterium with a generation time of 20 min could...
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Lecture 2.10 - GROWTH OF BACTERIAL POPULATIONS GROWTH OF...

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