The Ames Test
I’m sorry; I’ve been procrastinating on the article idea requests. It’s like 9:30pm and I’m an hour from home in a BART station. My train arrives in like half an hour :( Point being, this article is going to be about something relatively simple as I’m cranking this out in a train station / on a train.
Ok, but how much cancer???
The Ames Test is used to determine mutagenicity of a compound; in other words, this test quantifies the degree to which a certain compound causes mutations in cells. Thus, we can use this method to identify carcinogens (which cause mutations to start cancer).
We start with two plates of auxotrophic Salmonella bacteria. “Auxotrophic” means that they are a mutated form that has a metabolic deformity; in this case, the Salmonella are unable to metabolize and utilize the amino acid histidine. When plated on minimal media (which doesn’t have His), these bacteria will die. On the other hand, prototrophic bacteria are wild-type, and can survive on histidine-free media. To clarify, both plates have minimal media (which means no / very little histidine).
Each plate will have rat liver extract, which consists of various liver enzymes. The purpose of this is to mimic bodily conditions; some mutagens require modification by liver enzymes to activate and mutagenize. This liver extract will provide the necessary enzymes for this effect.
We then add the suspected mutagen to one plate. The other plate will be left as a control. After incubation, we measure and compare the number of colonies on each plate. The degree to which the experimental plate has more colonies relative to the control plate determines the mutagenicity of the compound. This is because colonies that successfully grew on the plate were revertants from auxotrophy to prototrophy (both plates can have natural revertants, which is why the control plate is necessary -- we need to determine and factor in the rate of natural reversion). We assume that this calculation is an accurate measurement of mutagenicity. In reality (please correct me if I’m wrong) I believe this would be an underestimate of mutagenicity, as the mutagens could cause other mutations, but they just won’t be visible because they don’t contribute to the histidine auxotrophy reversion. Perhaps since this problem exists across all Ames tests, relative mutagenicity of compounds may remain unaffected.
Here’s a nice picture:
You can learn more about this topic here:
WIKI SLAY: https://en.wikipedia.org/wiki/Ames_test
Also please keep the article ideas coming!! I will not be lazy every week I promise :)
