00:01
Okay, so the question here is basically asking what the stock cifu per milliliter concentration is.
00:11
That's just another way of saying, what is the bacterial burden in the stock solution? otherwise known as the sample, you know, the original samples.
00:23
So in this question, you basically plated of 100 miculators shown here in blue.
00:33
Of a 10 to the minus 7 dilution, and you put that on a plate, and the 148 colonies showed up on the plate.
00:44
So to calculate what the original burden is, we can basically use this one formula, which is cfu per mill, otherwise known as burden, bacterial burden, is equal to that's interesting there it is it's equal to number of colonies divided by dilution factor and volume plated so what does that mean? that means you can just plug in our values which you already have so the number of colonies that's how many colonies showed up on the plate so 148 colony forming units showed up on the plate.
01:57
Dillusion factor here is going to be 10 of the minus 7.
02:01
So 10 of the minus 7.
02:04
And the volume plated is going to be 100 micoleters.
02:12
Now, we can always rewrite this equation for a bit of better understanding.
02:22
So let's do that.
02:25
148, see if you can stay the same.
02:29
So that stays the same.
02:35
10 to the minus 7 can be rewritten as 1 over 10 to the 7th.
02:42
And 100 miculators is the same as 0 .1 milliliters.
02:48
And another way of writing 0 .1 is, of course, 1 to the 10th.
02:57
So then what does that mean? we can rewrite this equation, or rather simplify this equation even further.
03:08
So we still have the 148 cfu, and this is where we can do some mathematics to make the equation simpler.
03:24
When you divide within a fraction, if the denominator has a fraction, like we see here, 1 over 10 of the 7th, that bottom denominator, which is 10 to the seventh, gets brought up from the bottom to the top.
03:39
So that's the law of fractions.
03:41
So basically, this is one, stays down there, 10 to the 7th goes up top.
03:53
And then, same thing with 1 over 10, 1 in the middle of stays here, and then you multiply that by, and you bring the 10 to the top...