Safe Precautions for Incubating Petri Dishes: Using Saran Wrap and Plastic Bags at 37°C

Incubating Petri dishes is a common practice in microbiology, used for the growth and study of microorganisms. The process often involves maintaining the dishes at a specific temperature, typically around 37 degrees Celsius, which is the body temperature of a healthy human and ideal for the growth of many types of bacteria. A common question that arises is whether it is safe to use saran wrap and plastic bags around Petri dishes during incubation. This article aims to provide a comprehensive answer to this question, along with other related queries.

Why Use Saran Wrap and Plastic Bags?

Saran wrap and plastic bags are often used to seal Petri dishes to prevent contamination from airborne particles and to maintain humidity. The wrap or bag forms a barrier that keeps out unwanted microorganisms while allowing necessary gases like oxygen and carbon dioxide to pass through. This is particularly important when growing aerobic bacteria, which require oxygen for growth.

Is It Safe to Use Saran Wrap and Plastic Bags at 37°C?

Yes, it is generally safe to use saran wrap and plastic bags at this temperature. Most plastic wraps and bags are made from polyethylene, which has a melting point well above 37°C. However, it’s important to ensure that the plastic does not come into direct contact with a heat source, as this could cause it to melt or release harmful chemicals. Always place the dishes on a rack or shelf inside the incubator, not directly on the heating element.

Precautions When Using Saran Wrap and Plastic Bags

• Ensure the wrap or bag is securely fastened but not too tight, as this could restrict gas exchange.

• Do not use plastic that is colored or scented, as these could contain additives that may interfere with your experiment.

• Check the plastic regularly for signs of damage or melting.

• Always handle the dishes with clean, gloved hands to prevent contamination.

Alternatives to Saran Wrap and Plastic Bags

If you’re concerned about using plastic, there are alternatives. Parafilm is a commonly used laboratory film that is stretchable and self-sealing. It’s more expensive than plastic wrap but offers superior protection against contamination. Glass or silicone covers are also options, though they may not provide as tight a seal.

In conclusion, while it is safe to use saran wrap and plastic bags for incubating Petri dishes at 37°C, it’s important to take precautions to prevent contamination and ensure the safety of your experiment. Always use materials that are appropriate for your specific needs and conditions.