Why are Petri Dishes Incubated Upside Down?

When we are doing cell culture, after the inoculation is completed, the predecessors will have such an operation that they will turn the cell culture dish upside down. Many people will be curious about this move; why are Petri dishes incubated upside down? This article covers some of the reasons why you should invert the Petri dish:

Petri Dish Upside Down Reason:

Actually, inverting the cell culture dish does not mean inverting it immediately, as it is easy to pour the culture medium in the cell dish to other places and affect the experimental results.

  • 35mm culture dishFirst of all, the first reason is that inverted culture can prevent contamination. The purpose of inversion is to avoid that during the experiment, the water vapor in the cell culture dish condenses on the lid to form water droplets and drops into the cell culture dish to cause bacterial contamination. During operation, the cell culture dish will be exposed to the air, and microorganisms in the air may adhere to the water droplets or the culture dish cover, and the dripping of water droplets may introduce miscellaneous bacteria into the culture medium and culture, causing contamination and affecting the cultivation of target cell. At the same time, it also avoids the colonies caused by water droplets into flakes, which cannot be counted or separated. When the culture dish is inverted, the air in the plate is not flowing, and the bacteria will not settle to the surface of the culture medium. The evaporation of water will condense evenly on the surface of the culture medium, and the evaporation and condensation will form a balance, which will not affect the culture results. It is conducive to the volatilization of water on the surface of the medium, preventing the medium from falling off, and avoiding bacterial contamination. This is the main reason.
  • The second reason for Petri dish upside down is that this operation is convenient for observation and counting. When inverting for microbial culture, the spread of colonies in the culture dish can be controlled, and the colonies grown on the surface of the medium will not spread too quickly, which is conducive to the enrichment of nutrients and the formation of single colonies. This is not only convenient for experimental observation, but also makes it easier to identify colony characteristics and count during observation.
  • A third reason is that such placement facilitates the emergence of target cell cultures. After inversion, the problem of residual moisture can be avoided. Water droplets will not drip and break up colonies, and bacteria will not grow into biofilms on the surface, which is not conducive to the emergence of target cultures. If the purpose of culture is to collect the metabolites of bacteria, some bacteria are easily soluble in water, and inverting the culture dish can facilitate the collection, counting or separation of metabolites. And this is also beneficial for the target culture to use the nutrition of the medium to accelerate the growth rate!
  • The fourth reason is that such a placement makes it easy for the experimenter to take it, and it is easier to take and place it upside down. It is not like holding the petri dish upright and only picking up the lid when picking it up, causing the medium to be exposed to the air, which may cause pollution or cause the petri dish to fall and affect the experiment.
  • The last reason is that inverting the culture dish after inoculation can reduce the air flow on the surface of the medium, slow down the water loss and evaporation rate in the medium, make the medium not easy to crack, and fully maintain the environment where the target culture is easy to reproduce and survive. Facilitate the growth and propagation of target cultures. If it is not inverted, the medium is prone to cracking due to water loss. It is easier to dry out if the amount of medium added is not much.

The above is the reason why are Petri dishes incubated upside down, I hope it can help you to answer your doubts. If there is any experimental equipment that needs to be supplemented during the experiment, you can also contact our company. Our products will not let you down. We have a wide range of products with affordable prices and considerate services. Whether it is cell culture dish, universal pH paper, or whatever you need, we are willing to provide the best consumables produced with our heart to your laboratory. Our products are willing to be the strongest backing for your experiments.