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Published on: November 28, 2011
Bacterial culture preservation in frozen and dry-film methylcellulose
1Department of Plant Pathology, University of California, Berkeley, California 94720.
Abstract:
Forty-seven of 61 bacterial cultures, including strains of Pseudomonas, Xanthomonas, Erwinia, Agrobacterium, Corynebacterium, Serratia, Klebsiella, and Escherichia, remained viable after storage in frozen methylcellulose or in dried methylcellulose for up to 38 months. Pathogenicity remained intact for those strains tested. Bacteria were grown on a solid medium and then removed and placed in 1.0% methylcellulose (cellulose methyl ether) to make a final suspension of 10 colony-forming units (CFU) per ml. For storage in dried form, the bacteria-methylcellulose suspension was placed in a petri dish and dried in a forced-air incubator. After 24 h of storage at 25 degrees C, viable populations of 10 CFU/mg (equivalent to 10 CFU/ml) were recovered. Populations of 10 to 10 CFU/mg were recovered after storage of up to 38 months. Similar results were obtained in frozen methylcellulose. Survival was greatly enhanced when the growth medium for the bacteria was potato dextrose peptone rather than nutrient agar, yeast dextrose calcium carbonate peptone, or King's medium B. Addition of 0.1 M MgSO(4) to the methylcellulose suspension and to the resuspending liquid also increased survival and recovery from storage for some strains. Methylcellulose storage should be a simple, inexpensive, and reliable method of maintaining cultures for short or long periods of time.
Insights
Methylcellulose effectively preserves bacterial cultures, including important plant pathogens, for up to 38 months. This simple method maintains bacterial viability and pathogenicity for long-term storage.
Area of Science:
- Microbiology
- Bacteriology
- Culture Preservation
Background:
- Maintaining viable bacterial cultures is crucial for research and diagnostics.
- Traditional storage methods can be complex and costly.
- Developing simple, cost-effective preservation techniques is essential.
Purpose of the Study:
- To evaluate methylcellulose as a storage medium for diverse bacterial strains.
- To determine the long-term viability and pathogenicity of bacteria stored in methylcellulose.
- To identify factors influencing bacterial survival during methylcellulose storage.
Main Methods:
- Bacterial cultures were suspended in 1.0% methylcellulose.
- Suspensions were stored frozen or dried at 25°C for up to 38 months.
- Viable bacterial populations were quantified using colony-forming units (CFU).
- Pathogenicity was assessed for selected strains.
Main Results:
- 47 of 61 bacterial strains remained viable after 38 months in frozen or dried methylcellulose.
- Pathogenicity was maintained in tested strains.
- Survival was enhanced using potato dextrose peptone medium and MgSO(4) supplementation.
Conclusions:
- Methylcellulose is a simple, inexpensive, and reliable method for preserving bacterial cultures.
- This technique is suitable for both short-term and long-term storage.
- Optimized media and additives can further improve bacterial recovery.
