Defining the Petri Dish
A Petri dish is a shallow, cylindrical, lidded container that scientists, particularly biologists, use to culture, or grow, microorganisms. It provides a sterile environment and a surface for cells, bacteria, fungi, or small mosses to multiply for observation and study.
Section 2: Key Components and Types
A standard Petri dish consists of two parts: a flat, shallow base and a slightly larger lid that fits loosely over it. This design allows for gas exchange while preventing airborne contaminants from entering. They can be made from reusable, sterilizable borosilicate glass or, more commonly, from disposable, pre-sterilized polystyrene plastic.
Section 3: A Practical Example
In a common science experiment, a nutrient-rich gel called agar is poured into the dish's base and allowed to solidify. A cotton swab, after sampling a surface like a doorknob, is then gently streaked across the agar. The dish is lidded and incubated, and within a few days, visible colonies of bacteria will grow on the surface.
Section 4: Importance in Science
Petri dishes are fundamental tools in microbiology, molecular biology, and medicine. They are used to identify bacteria causing an infection, test the effectiveness of antibiotics (antibiotic sensitivity testing), cultivate cell lines for research, and conduct a wide range of experiments in a controlled setting.