Explain the Characteristics of Agar- Agar?
There are many characteristics, which make agar-agar, an ideal solidifying agent. These are:
(a) It has high gel strength, so it can be used at a concentration that won't inhibit microbial growth due to low water activity.
(b) It solidifies at 40 o C and once solidified it can liquefy at 85-90 o C. So it is ideal for isolation of thermophiles.
(c) It does not have nutritional value. It is used as a nutrient source only by some marine bacteria, so that in normal use, it is not liquefied by bacterial growth. Solid media provides a hardened surface on which microorganisms can be grown in the form of discrete colonies to get pure cultures. Solid medium can be used in petri plates as agar plates.