6 replies to this topic

[Yousuf]

A student grows a culture of E. coli in 50 ml of liquid medium contained in a 250 ml Erlenmeyer flask and decides to spread plate samples of the culture onto LB agar plates.  (LB stands for Luria Broth.  It’s simply a type of broth on which E. coli grow well.)  Before plating, she sets up several dilutions of the culture.  Then she plates 0.1 ml of each final dilution by spread plating.  She does this in duplicate for each dilution.  She then incubates all of her LB agar plates in the 37 ºC incubator and counts the colonies on each plate 1 day later.  Her results are as follows:

this link will show you the table
http://s277.photobuc...nt=homework.jpg

a) Assuming that the student carried out the serial dilution steps in the most efficient way possible (i.e. with the least necessary number of dilutions) write out all the steps she performed to get each total dilution factor.  Take into consideration the following facts:  The final volume at each dilution step was 10 ml and the highest single dilution factor she ever carried out was a 1/100 dilution or 10-2.

Edited by Yousuf, 30 September 2009 - 01:42 PM.

[GeorgeWolff]

Could this be homework or a take home test question?

[bob1]

Yousuf, on Sep 30 2009, 02:39 PM, said:

this link will show you the table
"http://s277.photobuc...n=view&current=homework.jpg"

I especially like the bolded bit in the URL above.

Edited by bob1, 30 September 2009 - 03:40 PM.

[Yousuf]

GeorgeWolff, on Sep 30 2009, 02:36 PM, said:

Could this be homework or a take home test question?

It's actually one of the questions in the exam last year and I left all of them blank because I don't know. I just want the answer for a review

[leelee]

You won't learn anything if we just give you the answer!! But we usually don't mind helping out on homework questions if you have at least tried to have a go. How about telling us what you think and then we can point you in the right direction if need be.......

[gebirgsziege]

CellSpecific.com, on Oct 1 2009, 08:36 AM, said:

This is one terrific community. Great advices.

So you think it is better to just give an answer? And after the test Yousuf has to go to the lab, do an exp. like the one in the question....what will happen next you think? Bioforumers are very helpful, but we will not do your homework.

So Yousuf, like leelee said: how would you answer the question?

[gebirgsziege]

CellSpecific.com, on Oct 1 2009, 06:07 PM, said:

Don't misunderstand. I am praising the fact that the forum is truly serious about helping and not just doing ones' homework. I'm new and I like what I see and agree with the advices to Yousuf to do the homework and seek feedback for help and clarification.

Sorry....misunderstood you. This happens sometimes with us non-native spakers; we get the wrong meaning of the words  

Edited by gebirgsziege, 01 October 2009 - 09:43 PM.