× Didn't find what you were looking for? Ask a question
Top Posters
Since Sunday
Home Q & A Board Laboratory Help Introductory Courses
New Topic  
Leen Leen
wrote...
Posts: 23
Rep: 0 0
12 years ago
Manny tells you that he diluted his bacteria. His dilution series was done using eppendorf tubes with a maximum of 1ml in them. The concentration of bacteria before starting was 1000/ml. The number of bacteria on his first plate was 33. This plate had 0.1ml of material from the first tube in the dilution series. What factor dilution did Manny use?
Read 459 times
1 Reply

Related Topics

Replies
wrote...
#1
12 years ago
Starting concentration = 1000 bacteria/mL.

Let the first dilution factor = F, so that the initial dilution was 1/F,
that is, the concentration in the first tube was 1000/F bacteria/mL.

0.1 mL of this was plated, which equals 1/10 of 1000/F = 100/F bacteria.

But this is equal to 33 colonies (equivalent to 33 viable bacteria).

Therefore, 100/F = 33, so F = 100/33, which is close enough to F = 3.

Now if we assume that F = 3, then 100/F = 33.3 (which is close enough to 33).
So it looks like the dilution factor was 3.
New Topic      
Quick Reply
Bold
Italic
Underline
Strikethrough
Subscript
Superscript
Insert Math Equation
Font Name
Font Color
Align left
Center
Align right
Bullet list
Numbered list
Insert a horizontal rule
Insert a table
Insert a Quote
View source
Explore
Post your homework questions and get free online help from our incredible volunteers
  1271 People Browsing
 106 Signed Up Today
Start New Topic Take the Tour CoursesNew Study Tools Topics Trending Browse by Textbook
Related Images
  
 311
  
 438
  
 881