Question

One ml of original bacterial culture is put into 199 ml of water in bottle x. What is the final dilution in bottle x?

Answer 1

Dilution = 1 ml of sample / (1 ml of sample + x ml of buffer)

here, buffer is water with 199 ml
so, dilution = 1/ (1+199) = ... ?

Answer 2

i was never good with biology but this seems pretty simple. It really is just a math equation.

Answer 3

200 is that it

Answer 4

actually, 1/200

Answer 5

.005

Answer 6

yes, 0.005 or 5 * 10^-3

Answer 7

If 1 ml from bottle x in problem 2 is placed into 199 ml of water in bottle y, what is final dilution in Bottle y

Answer 8

i am not sure about this,
but i think we just multiply the 2 dilutions to get final dilution,
that is,
(1/200) * (1/(1+199)) = 1/ (200*200)

Answer 9

are we talking about dilution factor?

Answer 10

then it is reversed

Answer 11

you're doing a concentration factor at the moment

Answer 12

A student make 1:10000 dilution of bacteria and puts 0.1 ml of this into I petri plate with medium. Te next day, there are 72 colonies growing on the plate. What is the cfu/ml of the original bacterial culture?

Answer 13

Yes I am niccompoop

Answer 14

so let us begin with
1 mL + 99 mL = 100 mL
dilution factor = 100 mL / 1 mL
the mL cancels out, and you are left with 100. therefore, the dilution factor (DF) is 1:100 dilution (10^2)

concentration factor = 1 mL / 100 mL
again, the mL cancels out, and you are left with 1/100. therefore, the concentration factor (CF) is 0.01 or 10^-2

Answer 15

this was your original problem.
I was just pointing out that you were doing concentration factor with the solution you had. the dilution factor is the opposite or reciprocal
DF = final volume / aliquot volume
where your final volume is aliquot + diluent
aliquot is a portion of the original sample.
diluent is the material that is used to dilute the sample

Answer 16

CF = aliquot volume / final volume

Answer 17

What about the third question I posted about the students plates

Answer 18

okay it says A student make 1:10000 dilution of bacteria and puts 0.1 ml of this into I petri plate with medium. Te next day, there are 72 colonies growing on the plate. What is the cfu/ml of the original bacterial culture?

if our dilution is 1:10,000
it must mean that our original sample was 1mL, and that the diluent was 9,999 mL

Answer 19

but it is asking you for CF, right?

Answer 20

CF = aliquot / final volume

Answer 21

Yes cfu/ml

Answer 22

how would you solve that based on ALL of the information I've given you?

Answer 23

if you have answer choices list them and I will explain

Answer 24

Is the answer 720000

Answer 25

how did you get that?

Answer 26

I need the solution and logic behind it

Answer 27

Bacause we were taught cfu/ ml iequal # of colonies times dilution factor

Answer 28

is your answer part of choices?

Answer 29

No

Answer 30

colonies * DF = 27 * 10^4 = 2.7 x 10^5 CFU per mL of bacteria

Answer 31

my bad, you put 72 … LOL
so it is 7.2 x 10^5

Answer 32

OMG I went dyslexic for a second, my apologies

Answer 33

Ok help with one more please

Answer 34

How much water do you need to make a 1:10 dilutions using 3 ml of your original bacterial culture.

Answer 35

but I am doubtful it is straightforward as that. because the amount that was put in the petri dish was 0.1 mL not 1 mL

Answer 36

But they don't ask for the dilution factor

Answer 37

0.1 mL is equivalent to 100,000 or 10^5 dilution factor

Answer 38

your dilution factor will dictate your CFU so you need to be careful

Answer 39

you essentially have 100,000 DF * 72 = 7,200,000 or 7.2 x 10^6

Answer 40

Ok what about the last question can you help me with that

Answer 41

I don't think you understand it

Answer 42

this is why I am hesitant to proceed with the other problem

Answer 43

I do I got it thanks

Answer 44

if you truly understand it, then you should be able to solve the next question

Answer 45

Is it 1/10 times 3 / 100

Answer 46

Tat is a start

Answer 47

How much water do you need to make a 1:10 dilutions using 3 ml of your original bacterial culture.
how about
3:30 = 1:10
see how it works?

Answer 48

Okay

Answer 49

you have 3 mL and you are looking for 1:10 DF
the definition of DF again is what?

Answer 50

Dilution factor

Answer 51

well you just gave me what DF stands for… what is the formula?

Answer 52

1 / dilution and volume

Answer 53

1/ dv

Answer 54

final volume / aliquot = (aliquot + diluent) / aliquot
(3 + x) / 3 = 10

Answer 55

3 plus 30

Answer 56

3 + 30 = 33
33/3 ≠ 10

Answer 57

30

Answer 58

I put 30

Answer 59

(3 + x) / 3 = 10
multiply both sides by 3, you get
\[3\times \frac{ 3+x }{ 3 }=10\times3\]

Answer 60

27 plus 3

Answer 61

there you go

Answer 62

that means you would add 27 mL of diluent to a 3 mL of aliquot of the sample in order to make a 1:10 dilution

Answer 63

Mthanks

Answer 64

Fan me

Answer 65

i hope I won't be seeing you ask the same type of questions again :P

Answer 66

http://inst.bact.wisc.edu/inst/index.php?module=book&type=user&func=displayarticle&art_id=103

you will use dilution and concentration in both biology and chemistry so it is important you learn it well.