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Growth Curve

About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.

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Growth Curve

Postby jackcreambun » Sun Apr 17, 2011 10:12 pm

Exam Revision question here. I've went through all my notes and searched the web to no avail, so I'm hoping someone here will be gracious enough to assist.
I'm going through previous exam samples and a sure question will be drawing a growth curve on semilog paper.

A] Use the graph paper provided amd draw a labelled growth curve for a mesophilic, strictly aerobic organism using the data in the table below. Initial growth conditions: 200ml Nutrient Brothat 200rpm at 37C
T(min) since inoculation(x axis): 0, 40, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330.
Cfu/ml (y axis): 1x10^6, 1x10^6, 1.5x10^6, 2.4x10^6, 4x10^6, 6.6x10^6, 1.01x10^7, 1.31x10^7, 1.32x10^7, 1.32x10^7, 1.31x10^7, 1.32x10^7

B] How long does the organism remain in the exponential phase? How long in Stationary phase?
C] From graph determine the mean generation time and then determine the growth rate constant.
D]If aeration was interrupted at 120min, draw on the graph what you would expect to observe for next 3 hours.

My main problem is drawing the graph. I have absolutely no idea how to use semilog graph paper.
I'm obviously not expecting somebody to do out the full question for me, just maybe some idea on how to start it.
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Joined: Sun Apr 17, 2011 9:53 pm

Re: Growth Curve

Postby protold » Mon Apr 18, 2011 6:32 am

Hola, in the semilog paper you see a lineal scale(abcises time min) and Y axis logaritmic with some non linear bands from 1 to 10. . So, to time 0 you have 10e6cells, so the first point is the cross of two axis being ordinates 10e6. The next block in ordinates starts in 10e7 (I havent here a paper to describe it to you)but in any piece of paper you have 4or 5 blocks .Inside each block you have divisions corresponding to the different units so betwen 10e6 and 10e7 the first line will be 2x10e6, the next 3x10e6 .......untill 9x10e6 under 10e7. Well making the points wich related cells and time, you will have a right line (exponential phase or log phase) , wich will drop at long times untill be horizontal(stationary phase). The generation time is done in exponential phase by the time that the population duplicates, so mark the times at 3x10e6 and 6x10e6 and calculate the difference in minutes. and the grow rate constant is (I think) the number of cells wich appears or double by unit of time, so if to grow from 3x10e6 to 6x10e6 spent 20 min the rate will be(6-3=3) 3x10e6/20. After aireation cut the cellular density will drop untill the cuture dead(I suposse). Wait for more answers while try undestand mine. Buena suerte
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Re: Growth Curve

Postby deangraziosi » Mon Apr 25, 2011 2:59 am

I had also face this situation, It seems me always hard to draw a perfect curves in the diagram. But gradually I learn and became easy for me to draw. I hope so you try for it with full of your heart and something might be happen with you. After all microbiology is very interesting subject to learn and know.
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Joined: Sat Apr 23, 2011 9:16 am

Postby Hirtsy6 » Wed Aug 17, 2011 11:30 am

Yes,I agree. First it was hard to draw a curve in the diagram, but then i just wanted to learn how to do it and finally i could do it. This is even rather interesting for me to do that.
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Joined: Wed Aug 17, 2011 11:24 am

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