MIC
February 4, Chapter 6

# February 4, Chapter 6 - 6 Microbial Growth What is Growth...

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6 Microbial Growth What is Growth In microbiology, growth is: Increase in number of cells, or population growth. Increase in cell size is cell growth -Never count cell, and pop growth 6.1 Binary fission A sexual reproduction A single organism divides to produce two progeny Fig A B C Form a Z ring, envaginates, some even though form firm septum Box 6.1 During the C phase, Septum forms in D phase Each cycle is called one generation Fig 6.3 Exponential growth is drawn in log. 6.2 Population Growth

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Generation tie (doubling time) The time require for a population of cells to double in number (Don’t needed to know-One E. coli cell could produce 4.7 times 10^21 in 24 hours One Bacillus subtilis can generate 1 time 10^12 in 20 hours) Microbial growth is exponential At Generation Cell number 0 [] 1=2^0 1 [] [] 2=2^1 2 [] [] [] [] 4=2^2 3 [] [] [] [] [] [] [] [] 8=2^3 N After n generation 2^2 How to calculate exponential growth N=Nsub0 times 2^n Nsub0= initial cell number How to calculate generation time (g) g= t/n g=generation time t=total time of exponential growth Q: A bacterium grows 10 generation in 3 hours. What is the generation time? 3hour/10= 18 minutes More generation time calculations Combining the two equations
N=Nsub0 times 2^n g= t/n Q1: E. coli grows from 1,000 to 8,000 cells in 1 hour. What is the generation time? t= 1 hour n=3 Answer: 60 min/3=20 minutes Q2: A Bacterium grows from 1 times 10^5 to 6.4 times 10^6 cells in 2 hours. What is the generation time? =120min/ (6.4 times 10^6 cells-1 times 10^5) Figure 6.4 Growth curve Lag Phase: a period where you don’t see growth in cells; adapting to the new media and environment. Exponential growth phase (aka log phase); grow at constant rate Stationary phase: Growth is limited due to nutrient depletion and waste inhibition: no change in cell number Death phase –Cell number declines due to cell death.

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