Mastering Petri Dishes: A Guide to Understanding Definition, Types, Uses, and Making

Reading Time: 8 minutes

A Petri dish, also known as a culture plate or a cell-culture dish, is a cylindrical or round, lidded container used in biology laboratories to cultivate and study microorganisms, such as bacteria and fungi. It was invented by Julius Richard Petri, a German bacteriologist, while working at the Imperial Health Office in Berlin. The dish is typically made of clear glass or plastic, with a shallow, flat-bottomed design and a transparent lid to shield the contents from airborne contaminants. Petri dishes play a crucial role in providing a controlled environment for the growth and observation of microorganisms. They are filled with a suitable growth medium that provides the necessary nutrients for the cells to proliferate. This medium can support the growth of various types of cells, allowing researchers to study their behavior and characteristics.

The introduction of the Petri dish was particularly significant in the field of antibiotics. In 1928, Alexander Fleming discovered penicillin, an antibiotic derived from the penicillium mold. He observed that the mold inhibited the growth of bacteria when grown in a Petri dish, leading to the development of this life-saving medication. Petri dishes are available in various designs, including double dishes, disposable or reusable options, and treated or non-treated surfaces for specific applications. They often come in multi-well designs, allowing for side-by-side comparisons or the growth of multiple cell cultures simultaneously. Some Petri dishes have graduated models to measure the growth area size accurately.

In laboratory settings, the use of Petri dishes with tight-fitting lids is crucial to prevent contamination. Vented or aseptic Petri dishes are also available, which provide a sterile environment while allowing gas exchange for certain applications. The importance of maintaining a contamination-free environment is particularly evident in pharmaceutical and hospital environments, where sterile conditions are essential.

Petri dish: features and variants

Petri dishes, crucial tools in microbiology and cell culture research, come in different materials and designs. Glass Petri dishes, made from borosilicate glass, offer heat resistance and transparency for direct examination under a microscope. Plastic Petri dishes, disposable and convenient, are widely used. These dishes have cylindrical shapes with varying diameters and heights. Some versions are squarish. The lid, with a close-fitting cover, prevents contamination and ensures smooth handling. Airflow is facilitated through small holes, preventing water condensation. Certain variants feature grids or cavities, allowing precise measurements and density assessments of cultures. Microplates enable cultivation and analysis of multiple samples simultaneously.

The choice between glass and plastic depends on experiment requirements. Glass offers reusability and heat resistance, while plastic provides convenience and eliminates sterilisation needs. Petri dishes remain vital in microbiology, enabling efficient research and analysis. Their adaptability to automated handling systems and cost-effectiveness make them indispensable tools for scientific advancements.

How to make your own Petri dishes using an injection moulding machine

Petri dishes are essential tools in laboratories for various biological experiments and culturing microorganisms. Making your own Petri dishes using an injection molding machine provides a cost-effective and efficient way to ensure a steady supply of these vital lab instruments. In this guide, we will outline the step-by-step process of creating Petri dishes using an injection molding machine, while emphasising the significance of sterilisation equipment and following proper instructions to guarantee high-quality results.

Gathering necessary materials. To start the process of making your own Petri dishes, gather all the necessary materials, including the bases for the dishes. The bases, typically made of clear, high-quality plastic, are essential for providing a transparent surface to observe the growth of microorganisms. Additionally, ensure you have access to an injection molding machine, which will be the primary tool for producing the Petri dish bodies. Properly maintained injection molding machines guarantee consistent and precise results.
Preparing the injection moulding machine. Before proceeding with the molding process, it is crucial to prepare the injection molding machine properly. Clean the machine thoroughly, ensuring there are no remnants of previous materials or contaminants that could affect the quality of the Petri dishes. Proper sterilisation of the injection molding machine is vital to avoid any cross-contamination during the production process, which could compromise the integrity of your experiments.
Following step-by-step instructions. Next, follow the step-by-step instructions provided for the injection molding machine. Understanding the machine’s settings, temperature requirements, and timing is essential for achieving the desired mold for the Petri dishes. This process requires precision, so carefully adhere to the guidelines to ensure the molds come out correctly.
Pouring the moulds properly. Once the injection molding machine is set up and ready, it’s time to pour the molds. Take care during this step to ensure the molds are filled uniformly, without any air bubbles or inconsistencies. Proper pouring of the molds will result in Petri dishes with smooth surfaces, suitable for cultivating microorganisms.
Sterilising the Petri dishes. After the Petri dish bodies are molded and cooled, it is crucial to sterilize them properly. Sterilization equipment, such as autoclaves or specialized sterilizers, should be used to eliminate any potential contaminants and ensure the Petri dishes are ready for laboratory use. Sterilization is a critical step to maintain the integrity of your experiments and avoid any unwanted bacterial or fungal growth.

The versatile uses of Petri dishes in laboratory settings

Petri dishes are indispensable tools in laboratory research, facilitating the study and testing of various microorganisms under controlled conditions. These transparent, shallow dishes provide an ideal environment to cultivate and observe the growth and behavior of cells, bacteria, yeasts, molds, and other organisms. Their broad range of applications extends to disciplines such as microbiology, biology, immunodiffusion studies, botany, entomology, and even chemistry. Let us explore the diverse uses of Petri dishes across these fields.

Microbiological testing and research. One of the primary uses of Petri dishes is in microbiology, where they serve as a platform for growing bacterial cultures and conducting antibiotic susceptibility testing. Agar, a gelatinous substance derived from seaweed, is used as a solid culture medium in these dishes. Researchers can add antibiotic discs to the agar, creating a gradient of antibiotic concentration that enables the evaluation of bacterial response to different treatments. This testing technique plays a vital role in understanding the effectiveness of antibiotic treatment against various strains of bacteria.
Cell cultivation and observation. Petri dishes also support the cultivation and observation of isolated cells and eukaryotic organisms. Whether it’s for studying the behavior of cells under controlled conditions or conducting immunodiffusion studies, Petri dishes provide a versatile platform. Researchers can use either solid agar or a liquid medium, depending on the specific requirements of their experiments.
Plant germination and asexual growth. In botany and agriculture, Petri dishes find application in the germination of seeds and the propagation of plants through asexual means. The transparent nature of the dish allows researchers to monitor the growth of plant tissues and assess the success of germination. Additionally, the controlled environment of a Petri dish is well-suited for exploring factors that influence asexual plant growth.
Entomology studies and small animal cultivation. Entomologists often employ Petri dishes to observe insects and small animals in a controlled setting. The dishes can provide an environment that supports the survival and growth of these organisms, allowing for detailed behavioral and physiological studies. The transparent surface of the dish enables easy observation using low-power microscopes or the naked eye.
Chemical and physical experiments. Beyond biological applications, Petri dishes serve various purposes in chemistry. They can be used to contain solvents, precipitates, or other substances during chemical reactions. Additionally, Petri dishes are employed in ovens and desiccators for sample storage and drying. Their transparency allows for easy inspection of the contents and facilitates precise measurements and analysis.
Contamination detection and surface mapping. Petri dishes are indispensable tools in contamination detection and surface mapping. These dishes can be used to collect samples from surfaces, such as kitchen counters, utensils, clothing, food preparation equipment, animal skin, and even human skin. The collected samples, when properly inoculated in Petri dishes, enable the growth of microorganisms, facilitating the detection and identification of potential contaminants. Surface mapping involves systematically collecting samples from different areas and mapping the distribution of microbial populations.

Types of Petri dishes: exploring varieties, sizes, shapes, materials, and features

Petri dishes play a crucial role in scientific research, and their selection depends on specific applications and laboratory requirements. Let’s delve into the various types of petri dishes available:

Sizes of Petri dishes

Petri dishes come in different sizes to accommodate diverse experimental needs:

Small dishes, with a diametre of 35mm, are commonly used for specific applications.
Petri dishes measuring 60mm and 90mm are popular in microbiology research.
For larger bacterial colonies and tissue culture experiments, a 100mm Petri dish is preferred.
The largest size available is 150mm, ideal for growing large colonies or cultures of cells, such as plant cells or yeast.

Shapes of Petri dishes

While circular petri dishes are the most common, specialty options with other shapes are also available. Researchers choose the shape based on their experiment’s requirements:

Round Petri dishes are widely used and suitable for general applications.

Square and rectangular petri dishes cater to specific research needs.

Materials for Petri dishes

Petri dishes are manufactured using various materials, each offering distinct advantages:

Glass. Borosilicate glass is a popular choice for its durability and ability to withstand heat, chemical sterilization, and radiation. Glass petri dishes have a smooth, non-porous surface, making them easy to clean and reusable. They find applications in research, academic, and high-temperature or chemical-intensive experiments.
Polystyrene. Lightweight, disposable, and cost-effective, polystyrene petri dishes are commonly used in clinical and industrial settings for routine microbiological testing. They are available with different surface treatments, allowing researchers to promote or prevent cell attachment based on their specific requirements.
Polypropylene. With superior resistance to heat and chemicals compared to polystyrene, polypropylene petri dishes are ideal for fieldwork, environmental testing, and industrial applications. Their lightweight and durable nature make them a preferred choice in demanding settings.
Cellulose acetate. Petri dishes made from cellulose acetate exhibit higher gas permeability, making them suitable for applications requiring elevated oxygen or carbon dioxide levels. They are also resistant to various chemicals and can withstand high temperatures.

Surface types

The surface of a petri dish can either be smooth or have a textured surface, offering specific benefits:

Smooth surfaces are commonly used for general applications.
Textured surfaces facilitate the growth of certain microorganisms or prevent bacterial swarming, making them useful in specialised experiments.

Lid types

Petri dish lids can be categorised as solid, vented, or semi-permeable, providing different functionalities:

Solid lids create a sealed environment, ensuring sterility and preventing gas exchange.
Vented lids allow for controlled gas exchange, supporting the growth of anaerobic microorganisms.
Semi-permeable lids enable researchers to regulate the humidity level within the dish, providing ideal conditions for specific experiments.

Specialised features

Stacked Petri dishes. Stacked Petri dishes feature multiple compartments, enabling efficient space utilization in crowded laboratory environments. Researchers can conduct simultaneous testing of multiple samples within a single setup.
Sections. Some Petri dishes include sections or compartments, allowing for the use of multiple types of media on a single plate or the testing of multiple samples simultaneously.

Coated Petri dishes

Coated petri dishes are treated with a layer of materials, such as collagen, fibronectin, laminin, or extracellular matrix proteins. These coatings promote cell attachment and growth, enhancing specific applications requiring cellular studies.

By understanding the diverse types of petri dishes available, researchers can make informed choices that align with their experimental requirements.

FAQs

How is a Petri dish used to grow bacteria? A Petri dish, also known as a Petri plate, is a shallow, circular glass or plastic dish filled with agar, a gel-like substance that serves as a nutrient medium for bacteria. To grow bacteria, the Petri dish is first inoculated by placing bacteria on the surface of the agar. The dish is then incubated under specific conditions, typically at 37 degrees Celsius, which provide an optimal environment for bacterial growth. The bacteria consume the agar as a source of food and multiply, forming colonies known as colony forming units (CFU’s). These colonies can be observed and studied for various purposes, such as identifying different types of bacteria or testing the effectiveness of antimicrobial agents. Thus, a Petri dish acts as a controlled environment where bacteria can thrive and grow, facilitating research and experimentation in microbiology and related fields.
Can polypropylene Petri Dish be autoclavable? Yes, polypropylene Petri dishes are generally autoclavable. Polypropylene is a type of plastic known for its heat-resistant properties, allowing it to withstand high temperatures without melting or deforming. Autoclaving is a sterilization method that utilizes high-pressure steam at elevated temperatures to kill microorganisms and ensure the cleanliness of laboratory equipment, including Petri dishes. The heat resistance of polypropylene makes it suitable for autoclaving, as it can endure the intense conditions of the autoclave without compromising its structural integrity. However, it is important to follow the manufacturer’s instructions to ensure proper autoclaving procedures and avoid any potential damage to the Petri dishes.
What is the function of Petri dish? The function of a Petri dish is to provide a suitable environment for the growth and cultivation of bacteria and fungi. It is a shallow, transparent glass or plastic cylindrical lidded dish that is used in microbiology labs. The dish contains a thin layer of agar, a gel-like substance that serves as a nutrient medium for microorganisms. By inoculating the surface of the agar with bacteria or fungi, researchers can observe and study their growth patterns and behaviors. Petri dishes are widely used in microbiology for various purposes, such as isolating and identifying different microbial species, testing the effectiveness of antibiotics or antifungal agents, and conducting research on microbial ecology. The use of Petri dishes in microbiology labs is extensive, with millions of them being utilized every year to facilitate scientific investigations and advancements in the field of microbiology.

Tim Williamson, a psychology graduate from the University of Hertfordshire, has a keen interest in the fields of mental health, wellness, and lifestyle.