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lecture 4 growth and fermentation

# lecture 4 growth and fermentation - Bacterial cells also...

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Bacterial cells also have a homolog of tubulin, FtsZ. Like tubulin, it polymerizes into filaments in a GTP- dependent manner.

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fts- mutant cells form filaments, “fail to separate”
During binary fission, replicated DNA molecules can be separated passively (or, rarely, actively)

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Growth among the prokaryotes usually occurs by binary fission. One cell gives rise to two identical daughter cells. This makes it easy to mathematically characterize bacterial growth--Doubling time is the time for binary fission, and the growth rate is the number of doublings per hour.
time cell # 0:00 1 0:20 2 0:40 4 1:00 8 1:20 16 1:40 32 2:00 64 2:20 128 2:40 256 3:00 512 3:20 1024 3:40 2048 4:00 4096 4:20 8192 4:40 16,384 5:00 32,768 5:20 65,536 5:40 131,072 6:00 262,144 Mathematically stated, N t =N 0 2 n . If we have a clock and a way of measuring cell number, we can figure out the generation time, g . The hard way to do this is mathematically: n= t/g log 10 N t = log 10 N 0 + n log 10 2 n = (log 10 N t - log 10 N 0 ) / log 10 2 n = t/g = (log 10 N t - log 10 N 0 )/0.301 g = 0.301 t / (log 10 N t - log 10 N 0 )

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time cell # 0:00 1 0:20 2 0:40 4 1:00 8 1:20 16 1:40 32 2:00 64 2:20 128 2:40 256 3:00 512 3:20 1024 3:40 2048 4:00 4096 4:20 8192 4:40 16,384 5:00 32,768 5:20 65,536 5:40 131,072 6:00 262,144 You could graph this: 0 50000 100000 150000 200000 250000 300000 0 100 200 300 time (minutes) number of cells
time cell # 0:00 1 0:20 2 0:40 4 1:00 8 1:20 16 1:40 32 2:00 64 2:20 128 2:40 256 3:00 512 3:20 1024 3:40 2048 4:00 4096 4:20 8192 4:40 16,384 5:00 32,768 5:20 65,536 5:40 131,072 6:00 262,144 There is a much easier way...use a “semi-log” graph.

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time cell # 0:00 1 0:20 2 0:40 4 1:00 8 1:20 16 1:40 32 2:00 64 2:20 128 2:40 256 3:00 512 3:20 1024 3:40 2048 4:00 4096 4:20 8192 4:40 16,384 5:00 32,768 5:20 65,536 5:40 131,072 6:00 262,144 1 10 100 1000 10000 100000 1000000 0 100 200 300 time (minutes) number of cells 200
Light scattering is a convenient proxy for cell number.

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lecture 4 growth and fermentation - Bacterial cells also...

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