I am working in the field of Medical Microbiology, My sample size is 300. The biggest problem with such a high number of microbial cultures is contamination and difficulty in maintaining them for longer periods. How do I maintain such large bacterial cultures in petri plates without contamination for a longer duration? Any suggestions, please
Some suggestions are:
Add antibiotics or antifungal agents (your organism should be resistant to those agents) to agar media to inhibit the growth of unwanted contaminants.
Seal stock culture plates tightly with parafilm to prevent air and contaminants from entering and Store them in a refrigerator set at a low temperature (4°C) to slow down bacterial growth. Lower temperatures can reduce the metabolic activity of contaminants.
Regularly subculture your bacterial cultures onto fresh plates to prevent contamination. Discard old or contaminated cultures promptly to maintain the integrity of your stock.
I agree with Phil Geis that Petri dishes is not the best way to store your strains. Frozen cultures at -80 is great for long term storage in glycerol, although if you are constantly using these strains many labs have traditionally kept agar slants, one per strain, which are usually viable for a month or a few months. But you should always have a permanent backup.
I totally agree with the 3 answers given so far. To store microbes for a longer period, prepare a sterile 50% glycerin and also do a 5-hour broth culture of your microbes. Pipet 0.5ML of your culture, and add the same volume of the 50% glycerin (0.5mL) to the culture, mix well and freeze at -80. Remember to use cryovial tubes to do the storage. Best wishes.
As above, store at -80°C, freeze dry, or even store under liquid nitrogen. If storing at -80°C - have approx. 50 % glycerol supplemented with 0.1 % yeast extract as the freezing medium
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