Serial Dilution Quesiton and Answer #1 - YouTube
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00:00:02 00:00:04 >> This screencast is created
00:00:04 00:00:06 to show you how to solve the following problem.
00:00:06 00:00:10 You're doing a pour plate serial dilution
00:00:10 00:00:13 using 10 to the minus one dilutions,
00:00:13 00:00:16 and starting with a culture of Pseudomonas aeruginosa
00:00:16 00:00:19 containing 3.5 times 10 to the nine cells.
00:00:19 00:00:22 First thing we would need to do is figure out
00:00:22 00:00:24 what kind of dilution we're having.
00:00:24 00:00:28 We're going to use 10 to the minus one dilutions,
00:00:28 00:00:32 which means one mill goes into nine mills of buffer,
00:00:32 00:00:34 and we're gonna need approximately nine tubes
00:00:34 00:00:36 because we have 10 to the nine cells.
00:00:36 00:00:37 So let's draw that out.
00:00:37 00:00:40 It's going to look something like this.
00:00:40 00:00:42 The next step would be to draw our dilutions
00:00:42 00:00:43 and our expected cell counts
00:00:43 00:00:47 along the bottom of the diagram, under each tube.
00:00:47 00:00:50 So we would have something looking like this.
00:00:50 00:00:54 We can see our 10 to the minus 9 dilution has 3.5 cells,
00:00:56 00:00:58 times 10 to the zero, which is equal to one.
00:00:58 00:01:01 So we have 3.5 cells in every one milliliter
00:01:01 00:01:03 of our 10 to the 9 dilution tube.
00:01:03 00:01:06 We have 35 cells in every one milliliter
00:01:06 00:01:08 of our 10 to the minus 8 dilution.
00:01:08 00:01:11 And we have 3.5 times 10 to the two,
00:01:11 00:01:14 which is 350 cells, in every one milliliter
00:01:14 00:01:17 of our 10 to the minus 7 dilution tube.
00:01:17 00:01:20 Next, we can draw in our Petri dishes
00:01:21 00:01:25 and indicate our target and bracket cell counts.
00:01:25 00:01:29 So 350 is one bracket, 35 cells is our target,
00:01:29 00:01:32 and 3.5 cells is our bracket.
00:01:32 00:01:34 The last step would be to indicate
00:01:34 00:01:36 which tubes we are taking our samples from,
00:01:36 00:01:38 and what plates we are putting them on,
00:01:38 00:01:40 indicating the volume.
00:01:40 00:01:44 So last, we would have one milliliter coming
00:01:44 00:01:48 from each 10 to the minus 7, minus 8, minus 9 dilutions,
00:01:48 00:01:51 and being plated on their representative plates.
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