Question: how do you detect different types of bacteria?

Katie Fala answered on 12 Nov 2019: last edited 12 Nov 2019 4:53 pm

That’s a good question, thanks shannonjs3! Traditionally microbiologists detected different types of bacteria by growing them on petri dishes. To check what type of bacteria it is, one way is to use selective agar which will only let a specific bacteria grow e.g. this agar plate will only let Listeria grow

or this is another one called EMB, only the E. coli bacteria will grow and produce that green metallic sheen that you can see.

However, it’s not possible to grow all bacteria on agar plates – some of them can be very finicky. For example, when we look at bacteria from the human gut, we can probably only grow about 30-40% of them. An alternate technique which is increasingly being used looks at bacterial DNA – this is called molecular biology. Instead of growing the bacteria, we can simply detect DNA sequences specific to the bacteria we are looking for. This is much quicker and doesn’t depend on the bacteria being alive or growable in the lab.
Let me know if you have more questions about this!