Petridish

🔬 Understanding the Petridish Dish:

A Petridish (also called a Petri plate or cell-culture dish) is a fundamental piece of laboratory equipment, typically made of shallow, cylindrical, transparent glass or plastic with a matching lid.¹ It was invented by German bacteriologist Julius Richard Petri.²

What is its Purpose?

The primary function of a Petri dish is to provide a controlled, sterile environment for the culture and observation of microorganisms (like bacteria, fungi, and yeasts) or cells.³

Key functions and uses include

How to Work with a Petri Dish (Basic Lab Procedure)

Working with in a laboratory, especially in microbiology, requires aseptic technique to prevent contamination.⁸ The general process involves:

1. Preparation and Sterilization:

   • The dish (if reusable glass) or the medium to be poured must be sterilized, typically using an autoclave (a high-pressure steam sterilizer).⁹ Plastic dishes are often pre-sterilized and disposable.

   • A growth medium (like nutrient agar) is prepared, sterilized, and cooled to about ¹⁰$45-50^\circ\text{C}$.

2. Pouring the Medium:

   • The sterile, cooled liquid agar is poured into the bottom of the Petri dish under sterile conditions (like in a laminar flow hood) and allowed to solidify.¹²

3. Inoculation:A small sample of the microorganism (the inoculum) is transferred onto the solid agar surface.¹³ This is often done using a sterile instrument like an inoculation loop or swab, using techniques like streaking to isolate individual colonies.¹⁴

   • The lid is immediately replaced. The dish should be labeled on the bottom (not the lid) with the sample name, date, and initials.¹⁵

     Incubation and Observation:

4. Disposal:Once the experiment is complete, the Petri dish and its contents must be decontaminated, usually by autoclaving again, before being safely disposed of as biohazardous waste.²⁰

The video “Bacterial Isolation on Petri Dish – Biology Lab Techniques” demonstrates the technique of streaking a Petri dish to isolate bacteria.²¹