The Petri dish is a shallow, circular, transparent dish, typically made of glass or plastic, with a slightly larger lid. This simple container provides a controlled environment for various scientific investigations. Its transparency allows for easy observation of contents without disturbing the enclosed conditions. Petri dishes are essential tools in scientific research and education, supporting a broad spectrum of biological and chemical studies.
Cultivating Microorganisms
The primary use of a Petri dish is for cultivating and studying microorganisms like bacteria, fungi, and yeasts. Scientists pour a nutrient-rich gel called agar, derived from seaweed, into the dish and allow it to solidify. This agar provides a solid surface and nourishment for microbial growth.
Before use, Petri dishes and the agar are sterilized, often using an autoclave, to eliminate pre-existing microorganisms. Once sterile, a sample containing microorganisms is spread across the surface. The lid, which fits loosely or has small gaps, allows for gas exchange while protecting the culture from airborne contaminants. This controlled environment enables scientists to grow pure cultures, identify pathogens, study growth patterns, and test substances like antibiotics.
Beyond Microbial Growth
While microbial cultivation is its most common use, the Petri dish is suitable for many other scientific applications. Its enclosed, transparent design allows for various controlled observations. For example, Petri dishes are used in plant tissue culture to grow plant cells, tissues, or small plantlets under sterile conditions.
They also serve as containers for small-scale chemical reactions, such as crystallization or precipitation, where a flat, transparent surface aids observation. Researchers use Petri dishes to observe the behavior of small insects or other invertebrates. They are also employed in educational settings and research for germinating seeds.
The Design and Its Inventor
The Petri dish’s design features a shallow, circular base with a slightly larger, overlapping lid. This construction allows the lid to rest over the base, providing a protective barrier. The transparent material, traditionally glass and now often plastic, ensures scientists can observe contents without opening the dish, which helps maintain sterile conditions.
The Petri dish is named after its inventor, German bacteriologist Julius Richard Petri. Working as an assistant to Robert Koch, Petri introduced his modified culture dish in 1887. This adjustment improved upon earlier methods by providing a contained and easily handled environment, significantly reducing contamination and simplifying microorganism culturing. Its enduring design has remained largely unchanged, making it a fundamental tool in biological research.