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#1
11-04-2012
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Bacterial Multiplication Calculation

A flask is inoculated to a density of 3 x 1000 cells/ml. What will be the density of cells in the culture after 50 minutes if the generation time is 20 minutes and the lag time is 10 minutes?
A. Same density
B. Half the density
C. Double the density
D. Four times the density
E. Given values insufficient to determine

#2
11-04-2012
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The cells are bacterial cells.
#3
11-04-2012
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D) four times the density..........but not sure..lag time confused me abit

thanks
#4
11-04-2012
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CC?

CC...I think it should be doubled after 30 minutes since no growth at 10 minutes in lag phase.
But the last 20 mins is confusing?but it should be in stationary phase?
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#5
11-04-2012
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Double the density?
#6
11-04-2012
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i change my answer to quadrupled .... 20 mins (x 2) 10 mins (stationary) another 20 mins (x2).....
#7
11-04-2012
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Its D. 4 times the density
#8
11-04-2012
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d

my ans is 4 times the density
#9
11-05-2012
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#10
11-05-2012
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Quote:
lag time 10 mins..then log phase-----doubling takes place every 20 mins...so, four times the density in remaining 40 mins......

thanks
 The above post was thanked by: IMGdoctor (11-05-2012)
#11
11-05-2012
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Quote:
 Originally Posted by venky2600 lag time 10 mins..then log phase-----doubling takes place every 20 mins...so, four times the density in remaining 40 mins...... thanks
Good to go venky..........that's correct answer.
 The above post was thanked by: venky2600 (11-05-2012)
#12
11-05-2012
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C. Double the density ?????

Quote:
 Originally Posted by subbi A flask is inoculated to a density of 3 x 1000 cells/ml. What will be the density of cells in the culture after 50 minutes if the generation time is 20 minutes and the lag time is 10 minutes? A. Same density B. Half the density C. Double the density D. Four times the density E. Given values insufficient to determine
Dude you really know how to test our easy looking but always making confused topics.
So thats how i approach question-
Lag time- no particular cell growth

generation time- rapid dividing phase (may bacteria's undergo mitosis. So guess it it be 2 X original density)

but in all together 50 mins we should include stationary and death phase. (but as there will be no particular growth)
So not sure what will be the final answer.

As i didn't did much of reading recently but If you will just not answer question but also discuss your approach. Thanks
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#13
11-05-2012
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Quote:
 Originally Posted by subbi Good to go venky..........that's correct answer.
Ok so this means, we don't consider stationary phase???
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#14
11-05-2012
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Quote:
 Originally Posted by koolkiller88 Dude you really know how to test our easy looking but always making confused topics. So thats how i approach question- Lag time- no particular cell growth generation time- rapid dividing phase (may bacteria's undergo mitosis. So guess it it be 2 X original density) but in all together 50 mins we should include stationary and death phase. (but as there will be no particular growth) So not sure what will be the final answer. As i didn't did much of reading recently but If you will just not answer question but also discuss your approach. Thanks

Fren it goes like this, generation time is the time taken by the cells to double which is possible only bye division i.e. only in log phase...............here in total of 50 mins time, lag phase is 10 minutes (lag phase is the one where cells are resting and no. of cells do not change at all)................remaining time is 40 minutes.............if cells double in 20 minutes (in question generation time=20 minutes), then in 40 minutes, it'll double two times i.e. four times the original..................hope this helps............thanx.
#15
11-05-2012
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But after one multiplication wont that have lag phase again??

#16
11-05-2012
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@subbi---thanks..actually at first i wasn't sure...but after looking at @obinocle approach..i concluded my answer....

@koolkiller88 @neelima208--------adding a point to subbi's explanation.......unless the bacterial growth specifies(like for ex--10000cells/ml is limit),doubling time continues as long as the time given(i mean they will be in log phase)...we should consider the whole time given under doubling time only..no entry to stationary phase too

hope this understands..thanks
 The above post was thanked by: koolkiller88 (11-05-2012), neelima208 (11-05-2012), subbi (11-05-2012), trupti (11-06-2012)
#17
11-05-2012
 USMLE Forums Addict Steps History: --- Posts: 110 Threads: 4 Thanked 32 Times in 28 Posts Reputation: 42

Quote:
 Originally Posted by venky2600 @subbi---thanks..actually at first i wasn't sure...but after looking at @obinocle approach..i concluded my answer.... @koolkiller88 @neelima208--------adding a point to subbi's explanation.......unless the bacterial growth specifies(like for ex--10000cells/ml is limit),doubling time continues as long as the time given(i mean they will be in log phase)...we should consider the whole time given under doubling time only..no entry to stationary phase too hope this understands..thanks
Vencky2600
I don't get it right.pls explain alittle

From lag to log phase and then to stationary and so.
Why do you stop at log phase?
I reasoned it should cont. to remaining phases after a single doubling time??
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#18
11-05-2012
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,186 Threads: 119 Thanked 815 Times in 434 Posts Reputation: 825

Quote:
 Originally Posted by chux Vencky2600 I don't get it right.pls explain alittle From lag to log phase and then to stationary and so. Why do you stop at log phase? I reasoned it should cont. to remaining phases after a single doubling time??
k i'll try to explain with example.....

1) if bacterial density is 3000 cells/ml and lag time 10mins, doubling time is 20mins. and if the population limit is 7000 cells/ml ...so what happens in 40 mins...?................ans---here the bacterial growth limit is specified...so lag time -10mins ,then log phase -20mins(so doubles-6000cells/ml) then remaining time-10mins(considered as ststionary phase----1000cells/ml)

2) if bacterial density is 3000 cells/ml and lagtime-10mins ,doubling time is 20mins.............what happens in 40 mins---------?
ans-----------here growth is not limited........so, lag time--10mins...then log phase-----20mins(doubles--6000cells) and the doubling continues again till the time given in question..(so here again 20 mins----12000 cells/ml---which is 4 times the density of initial sample)
the question didnt tell that the bacterial growth is stopped after 50 mins or likewise(it just asked us to calculate the growth till 50 mins).......so it continues in log phase only..............

hope it clears ......if you didnt get it,read this(but i think it's vast).......http://en.wikipedia.org/wiki/Bacterial_growth...

thanks

 Tags Microbiology-, Step-1-Questions

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