Microorganism Culture Methods - Most of the industrially useful bacteria and fungi are cultured on either a solid medium or a liquid medium with a support. In either case, the medium should contain all essential ingredients needed for optimum growth of that particular micro organism. Solid medium is generally prepared by melting agar at 100°C (in water) and then solidifying it at about 45°C.

The medium, which is still in a molten state, is poured into a suitable container and is allowed to cool and solidify. It is then inoculated by dipping a needle into the suspension of bacteria or fungi and drawing this needle right across the surface of the medium.

After a few days of inoculation, colonies of micro organism appear on the surface of the medium. In liquid cultures, all essential nutrients are dissolved in water. Agar or any other solidifying agent is not needed.