12 The generation time of a culture is defined as 世代时间The generation time of a culture is defined asA. the time it takes a cell to divide.B. the time it takes the culture to begin growth.C. the interval of time between the end of log phase to the stationary phase of growth.D. the period of time it took for the organism to appear on earth.E. how long the culture has been growing.
13 Generation Time (minutes) BacteriumMediumGeneration Time (minutes)Escherichia coliGlucose-salts17Bacillus megateriumSucrose-salts25Streptococcus lactisMilk26Lactose broth48Staphylococcus aureusHeart infusion broth27-30Lactobacillus acidophilus66-87Rhizobium japonicumMannitol-salts-yeast extractMycobacterium tuberculosisSyntheticTreponema pallidumRabbit testes1980
14 Calculation of Generation Time G = t/nG ---generation time (time for the cells to divide)t---time (interval in hours or minutes)n---number of generations(number of times the cell population doubles during the time interval)
15 N1 = number of bacteria at the beginning of a time interval N2 = number of bacteria at the end of the time intervalN2 = N1 × 2n(This equation is an expression of growth by binary fission)Solve for nlog N2 = log N1 + nlog2n = log N2 - log N1 log2n = log N2 - log N1 0.301n = 3.3 log N2/ N1Solve for GG = t/nG = t log N2/ N1
16 A bacterium with a generation time of 0 A bacterium with a generation time of 0.5 hours will grow from a population of 103 to 109 cells, in about how many hours?A. 25B. 3C. 40D. 20E. 10Solve for GG = t / nG = t log N2/ N1
17 Bacteria from_______ phase can be used to screen medicine Use of theGrowth curveBacteria from_______ phase can served as “seed” to another culture medium effectively, to decrease the lag phaseBacteria from_______ phase have the most typical morph－ological, biochemical and physiological featuresBacteria from_______ phase can be used to screen medicine
18 If at time 0 you had 10 million cells and two hours later had 40 million cells, what is the generation time?