00:04
A 0 .000001 dilution or 10 to negative 7 dilution is performed on a culture of bacteria in order to perform viable plate count.
00:15
So from the dilution, 0 .1 ml of solution is plated on solid media and 260 colony forming unit grow on a plate.
00:24
How many bacteria are in a single ml of original culture? expressed as in two decimal place.
00:32
So the very first step, you want to calculate the diluted culture, diluted culture cell density.
00:45
For the diluted culture, you start out with a colony number of 260.
00:51
So the number of cfu divided by the volume plated.
00:56
The number of cfu is 260 and the volume plated is 0 .1 ml.
01:17
So you end up having 2 ,600 cfu per ml.
01:22
So this is going to be the diluted cell density.
01:27
Now remember in the very beginning, we talk about the dilution itself.
01:31
So this is a 10 to negative 7 dilution.
01:34
This means that the factor equals one divided by 10 to negative 7, which is 10 to the positive 7.
01:50
So in that case, our original is going to be the diluted version, 2 ,600 cfu per ml times the dilution factor 10 to the seventh because the original cell density is 10 to the seventh power more concentrated than the diluted stock.
02:18
So we can write them down in scientific notation, 2 .6 times 10 to the 10th cfu per ml.
02:30
So this is the first question.
02:37
So the second question, how many ml of original sample are required to produce a final dilution of 10 to negative 1 in a total volume of 1 ml? so we know that this is one and two.
02:56
You want to make a 10 to negative 1 dilution and then a total volume is 1 ml.
03:03
So we know this formula, dilution factor or dilution itself equals the original sample volume divided by the total volume.
03:21
So we know that the dilution is 10 to the minus 1 and the original volume is a none...