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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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