Need help in microbiology...?

Question

In Pour Plate method for isolation of bactria, why is it that the colonies growing beneath the surface are quite small?

Answer 1

The bacteria grows faster on the surface of the agar during incubation because it is on the surface (i.e. it's exposed). The bacteria inside the agar is surrounded by the medium and somewhat "protected" by it, causing slower growth.

Answer 2

oxygen diffusion is slower under the agar...

try for a thinner coat of agar for bigger colonies or place in a higher O2 incubator

hope this helps