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Preservation of bacteria for short term
- 1. Methods to maintained and preservation of microbes BY HASNAIN AKMAL UNIVERSITY OF OKARA
- 3. Preservation To maintain pure culture for extended period of time without any genetic change. Objectives: To maintain isolated pure culture for extended period. To avoid contamination. To restrict from mutation.
- 4. Methods of preservation There are two methods for preservation. Short term preservation Long term preservation
- 5. Short term preservation Periodic transfer of fresh media. Preservation by using Glycerol Storage at low temperature.
- 6. Periodic transfer of fresh media or sub culture Strains can be maintained by periodically preparing a fresh culture from stock culture. The culture medium, the storage temperature, and the time interval at which the transfers are made vary with the species and must be handle before treated. The temperature and the type of medium chosen should support a slow rather than a rapid rate of growth so that the time interval between transfers can be as long as possible. Many of the more common heterotrophs remain viable for several weeks or months on a medium like nutrient agar.
- 7. Disadvantage The transfer method has the disadvantage of failing to prevent changes in the characteristics of a strain due to the development of variants and mutants.
- 9. Preservation by Glycerol bacteria can be frozen by using 15% Glycerol. In this method 30-50% glycerol can be added. Equal amount of glycerol and culture broth are mixed and than passed into tube and than frozen at -10. Viability vary from species to species. E.coli viable for 5 months, Heamophilus influenza viable for 4 months and Neisseria meningtidis for 6 months.
- 11. Preservation at low temperature Can be preserve at low temperature when maintained at 4 c for 2-5 days. At low temperature bacteria metabolic activity slower down and small quantity of nutrients required. Disadvantage Can not be used for long term because toxic chemicals accumulated and kill bacteria.