Im planning to do some BAC maxi preps, a total of 8, and due to the restrictions in terms of equipment, i would only be able to do 2 at a time since only two 1000mL Erlenmeyers fit in the shaking incubator.
I was wondering if i could do all of the starter cultures together and then leave some at 4ºC to then do the maxi cultures the following days (so the maximum time a culture would be at 4ºC would be around 3 days).
My concern is that by putting them at 4ºC ill be losing the inherent efficiency of a starter culture, i.e., to have actively dividing bacteria, in the logarithmic phase.
For plasmid extractions it is best to do it with fresh cultures.
Since you are talking about starter cultures then I think you will be fine. While you might find the 2 and 3 day culture will start slightly more slowly than the fresh starter, I don't think it will be very significant.
I would use fresh cultures when you are doing maxi preps and not cooled starter cultures if possible. This will result in better yield.
Alternatively, you could make small starter cultures (overgrown bacterial culture) in ~100 ml media medium and freeze as ~40 ml aliquots at -80degC. When you are ready to do your maxi prep, just use the thawed frozen aliquots. Leave the large batch media at RT overnight to compensate for the cold starter culture. I would advise this over storing the entire starter culture at 4degC over a few days.
Yes, you can leave (or store) starter culture at 4ºC but you need to consider the impacts on the efficiency and yield of your maxi preps. As you mentioned, your main purpose is to inoculate the starter culture to larger culture. when you cool the culture to 4ºC, the growth, of course, significantly slows down, and they transition into a stationary phase. While the bacteria won't be actively dividing when you take them out of the fridge, they can quickly return to Log growth once reintroduced to a favorable environment (warmth and fresh medium). You need to consider recovery time as well. There might be a lag phase as the bacteria acclimate to the new conditions and return to active growth. This could slightly extend the overall culture time needed to reach the desired density for your maxi prep.
My take is that starter culture preserved at 4oC for up to 24 hours will not have any significant population change. This is due to inactivation of microbial enzymes. However, if left for longer than this period, cell start entering a decline phase and therefore a lower population in the starter culture.
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