What are the technical precautions for isolation and inoculation of pure bacteria?

The matters needing attention of pure bacterial isolation and inoculation technology are as follows:

1) dilution problem

When the pure strain is isolated, it is nothing more than diluting the bacterial liquid to a certain gradient and coating it on LB medium. If the dilution is not good, the bacteria will grow too densely, or the bacteria will not grow at all. The optimum dilution gradient is that the number of colonies on the plate is between 30 and 300. At this time, the morphology of colonies can be clearly seen, which is convenient for picking a single colony;

2) Contamination of miscellaneous bacteria

Because the inoculation is usually carried out in a nutrient-rich organic medium, this medium is suitable for the growth of any bacteria. In the process of operation, there are many invisible bacteria in the air and on the table. Before inoculation, all used instruments and culture media must be sterilized at 12 1 Celsius for 20 minutes to 30 minutes. When pouring the plate, it is best to pour it when the culture medium is still hot to reduce the infection of miscellaneous bacteria. All operations are best carried out on a clean workbench. If there is no clean workbench, light it with two alcohol lamps, wipe the desktop with alcohol, and operate between the two alcohol lamps.

To sum up, in order to isolate and inoculate bacteria, operators must completely ensure the infection of miscellaneous bacteria, operate skillfully, and have the strictest requirements on temperature and cleanliness.