Why is agar used for observing the growth of bacteria?

Question

Biology Question

Thanks

Answer 1

Agar is a solidifying agent!

It doesn't have any nutrient factors.

Bacteria can't utilize the polysaccharides for carbon source.  

Bacteria can grow on it without inhibiting the growth.

Answer 2

Agar is used to solidify the culture medium to provide a solid surface for bacterial growth. A solid surface allow each bacterial cell to grow into an individual colony.

Answer 3

I suppose because

a) It contains nutrients, so the bacteria will be able to grow + reproduce, and

b) It's clear, which makes it easy to observe the bacteria growing.

Answer 4

Agar (aka agar-agar from red seaweed) is a polysaccharide polymer and provides the support structure in the bacteriological medium.  Agar gives a solid support so that bacterial colonies can form on the surface of the agar medium while allowing the diffusion of nutrients and water.  The structural function of agar in bacteriological media is similar to the function that gelatin has in Jell-O.  In bacteriological media, agar and nutrients are added together and the specific nutrients are chosen for the particular type of bacteria you want to grow and for the conditions under which you want the bacteria to grow.  Agar is used rather than gelatin because agar isn't broken down by most bacteria.