Detection Methods Flashcards
What are the characteristics of a good indicator organism?
See slide 3. Detection
What are the 4 different styles of detection methods used for microorganisms?
See slide 12. Detection
What glow-inducing compound is involved in the biological reaction used in the ATP detection method?
See slide 13. Detection
Can you explain the basis behind how this test works?
Why do we usually have to enrich a sample before it can be used in a lateral flow kit?
Because a lateral flow kit can only detect bacteria at a 10^4 concentration. In order to eliminate false positives, the sample is enriched so all possible contaminants become present at a detectable level.
Why do injured organisms grow better on enrichment media versus selective media?
Selective media contain agents that only allow certain types of microbes to grow (like bile salts) with put stress on injured microorganisms. Enrichment media only contains nutrients and no selective agents, putting less stress on injured cells and allowing them a better growth environment. See slide 7 for a graphical representation.
What 4 ingredients do you need in order to run a PCR reaction?
See slide 13.
Define enrichment broth, differential agar, and selective agar.
Go back to the slide 2 of the detection method lecture
What are three tests commonly used to detect coliforms in water (mainly, can be used for food), and what is the shortcoming of each?
Revisit slide 6 from detection lecture; I mostly want you to appreciate that indicator organism tests don’t necessarily give you straight-forward results.
How does oxygen affect the recovery of injured cells?
Slide 11 of the detection lecture…oxygen radicals are damaging to bacteria, but for the most part “healthy” bacteria can tolerate them. If you are plating a food product that has a lot of injured cells, the radicals naturally present in the atmosphere might prove damaging enough that when plated onto agar, these cells die rather than repair themselves and grow into colonies that you can count.
Can you explain in words, the basis behind the lateral flow assay, and PCR, for detecting microorganisms?
Make sure you can. Understanding what these tests are detecting and the basis for how they work is important for the short answer section.
What is the advantage of incorporating a dye such as SYBR Green into a PCR reaction?
Allows you to monitor the formation of double stranded DNA during a PCR reaction, so there is no need to run a gel to verify that the reaction worked.
What are the advantages and disadvantages of lateral flow and PCR as detection methods?
Again, these points are important (slides 8 and 22 from last lecture), so make sure you know them!
