Question

What is pure culture?

Answer 1

Pure culture is the artificial culturing of only a single type of organism which rarely exists naturally but can exist in mixed culture. In simple terms, we have to isolate the single pure colony of bacteria that exist in mixed colonies of Bacteria.

Complete answer: In the pure culture we isolate the bacteria from the mixture of bacteria and after isolation, these are to be cultured.
This method was first introduced by Joseph lister working on bacteria.
Isolation of pure culture:
After the formation of culture media, it is poured into the petri dish and then placed in the incubator for two to three days.
Isolation is done by three methods:

1. Streak plate method: Streaking is a process of spreading the microbial culture with an inoculating needle on the surface of the media. First of all, we will sterilize the inoculating needle by flame, and then it is dipped into the sample containing the mixture of bacteria. some bacteria are picked up by this needle. After that spread these bacteria on the Agar plate. In this way, bacteria grows and forms a colony. and desirable colonies can be easily isolated.
2. Pour plate methods: in this method, a bacteria sample is mixed with warm agar and then this sample is poured on a sterile plate. This sample is swirled and allowed to solidify and then this plate is incubated which allows the growth of the bacterial colony. and this can be easily isolated.
3. Spread plate methods: This is the best method to isolate the pure colonies. In this technique, the culture media is not mixed with agar medium, instead, it is mixed with normal diluted saline. And then a small amount of it is spread on the agar plate. This helps in the formation of colonies.

There are various types of pure culture:

1. Streak culture
2. Stab and stick culture
3. Stock culture
4. Starter culture
5. Enrichment culture
   And the instrument which is required for the isolation of pure cultures are:
6. Autoclave
7. colony counter
8. hot air sterilizer
9. incubators
10. Ultraviolet lamps
11. centrifuge
    Culture media consist of:
    Combination of essential nutrients which is required for the cell growth like carbon source, nitrogen source, energy source and mineral salts like phosphates, sulfates, chlorides carbonates of K, Mg and Ca. Apart from this, a pH of 7.2-7.4 is necessary.
    Method and preservation of culture:
    Once a culture is prepared, it is necessary to preserve it and this can be achieved by the Refrigeration paraffin method and cryopreservation.

Note: Cryopreservation is the process of storing and preserving the cell, tissue, or any organ at very low temperature (at about $- {196^ \circ }F$) in liquid nitrogen and in this way viability of that cell or tissue can be maintained.