








USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam 

Thread Tools  Search this Thread  Display Modes 
#1




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




The cells are bacterial cells.

#3




D) four times the density..........but not sure..lag time confused me abit
thanks 
#4




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?
__________________
with God,nothing is impossible...PREMATCHED!!! To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. 
#5




Double the density?

#6




i change my answer to quadrupled .... 20 mins (x 2) 10 mins (stationary) another 20 mins (x2).....

#7




Its D. 4 times the density

#8




d
my ans is 4 times the density

#9




Please give your calculations.............thank you.

#12




C. Double the density ?????
Quote:
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
__________________
One day i will infect these microbes and they will search for "AntiMEbiotic".... To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. 
#13




Ok so this means, we don't consider stationary phase???
__________________
One day i will infect these microbes and they will search for "AntiMEbiotic".... To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts. 
#14




Quote:
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




But after one multiplication wont that have lag phase again??

#16




@subbithanks..actually at first i wasn't sure...but after looking at @obinocle approach..i concluded my answer....
@koolkiller88 @neelima208adding a point to subbi's explanation.......unless the bacterial growth specifies(like for ex10000cells/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:  
#17




Quote:
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??
__________________
focus 
#18




Quote:
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...?................anshere the bacterial growth limit is specified...so lag time 10mins ,then log phase 20mins(so doubles6000cells/ml) then remaining time10mins(considered as ststionary phase1000cells/ml) 2) if bacterial density is 3000 cells/ml and lagtime10mins ,doubling time is 20mins.............what happens in 40 mins? anshere growth is not limited........so, lag time10mins...then log phase20mins(doubles6000cells) and the doubling continues again till the time given in question..(so here again 20 mins12000 cells/mlwhich 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, Step1Questions 
Thread Tools  Search this Thread 
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Bacterial DNA Replication!  alfjof  USMLE Step 1 Forum  7  05302012 12:50 PM 
calculation without calculation ???  MedPharm  USMLE Step 1 Forum  5  02242012 12:55 AM 
Bacterial Vaginosis; An STD or Not!  tinhi  USMLE Step 1 Forum  2  05262011 11:16 PM 
Bacterial Multiplication Numbers  deyneko  USMLE Step 1 Forum  4  12252010 06:05 AM 
Calculation of GFR!  Kabutar111  USMLE Step 1 Forum  4  07222010 10:59 AM 
