What should be done to prevent contamination of agar plates during experiments?

To prevent contamination of agar plates during experiments, it is essential to store the dishes upside down with the lids tightly secured. This approach minimizes the risk of airborne contaminants settling on the agar surface, which is particularly susceptible to bacteria and mold growth when exposed.

Keeping the dishes covered creates a barrier against potential sources of contamination, such as dust, microbes, and spores that may be present in the laboratory environment. Storing them upside down also helps prevent condensation that can form on the lid, which might drip onto the agar and promote unwanted microbial growth. Together, these practices contribute significantly to maintaining the sterility of the dishes, ensuring reliable experimental results.

Other methods, such as using chemical sterilizers or inoculating at room temperature, do not address the primary issue of preventing cross-contamination from the environment directly. Keeping dishes uncovered creates a high risk of contamination from the air. Therefore, tightly securing the lids while storing them upside down is the most effective strategy for preserving the integrity of the cultured samples.