Question on the "Pour plate" method of bacterial analysis

[Probo]

Why, in this method, when compared to "Spread plate", does it have less tendency of interference between one colony and another?

[CharonY]

Have you done either of these methods or do you know theoretically how they are done? Can you think of a reason why spreading could cause an challenge compared to pouring?

[Probo]

2 minutes ago, CharonY said:

Have you done either of these methods or do you know theoretically how they are done? Can you think of a reason why spreading could cause an challenge compared to pouring?

I have not done any because the pandemic suspended the lab practices before I could have contact with it, but I imagine that speading would sort of mixture the colonies, and the results would be less accurate, but I am not certain if that is the case.

[CharonY]

No, it is not the mixing. In fact, both methods require the dilution of the cells you want to count. Also, in both cases it is important that your dilution is high enough that you only get a limited number of colonies, so that you can actually count them.

The main difference (actually there are a few more, depending on the bacterium and specific type of pouring medium, but we can ignore that for now), is how you spread your cells. Using the overlay, you swish it a little bit around and let it settle, in the other you have to use a spreader. In principle both work pretty much equally well if you have the right technique, though.