Discovering the Microbial World: Create Your Own Agar Plates

The activity below was contributed by Dr. Sandra Wilks during our podcast interview.

Have you ever wondered about the hidden world of microbes that surround us? Although these microscopic organisms are invisible to the naked eye, there are ways to catch a glimpse of their fascinating diversity and beauty, which you’ll discover how to do as you read on.

But first, we’ll begin with some background information on the importance of studying microbes and why the petri dish is a crucial tool in microbiology, and then we’ll move on to the activity of creating your own agar plates.

The Importance of Studying Microbes

Microbes are incredibly important and have a profound impact on our lives and the world around us. Understanding and studying these microscopic organisms is crucial for several reasons. Let’s explore the significance of studying microbes:

1. Ecological Balance and Nutrient Cycling: Microbes play a vital role in maintaining ecological balance and nutrient cycling in various ecosystems. They are responsible for the decomposition of organic matter, breaking down complex substances into simpler forms that can be recycled and reused by other organisms. By studying microbes, scientists can better understand the intricate processes that sustain life on Earth.
2. Human Health: Microbes have a significant impact on human health, both as beneficial and harmful organisms. Many beneficial microbes reside in our bodies, contributing to our overall well-being. For example, the human gut microbiota helps with digestion, immune system regulation, and the synthesis of essential vitamins. Conversely, harmful microbes can cause infectious diseases. Studying these microbes enables us to develop strategies for disease prevention, diagnosis, and treatment.
3. Agriculture and Food Production: Microbes play a crucial role in agriculture and food production. Certain microorganisms, such as nitrogen-fixing bacteria, form symbiotic relationships with plants, enriching the soil with essential nutrients. Others can act as biocontrol agents, combating plant pathogens and reducing the need for chemical pesticides. Furthermore, the fermentation processes carried out by microbes are essential in producing various food products like cheese, yogurt, kombucha, kefir, and bread. By studying microbes, scientists can improve agricultural practices, enhance food safety, and optimize production methods.
4. Environmental Conservation: Microbes are key players in maintaining environmental balance and sustainability. They participate in processes such as bioremediation, where they break down pollutants and contaminants in soil, water, and air. Microbes also contribute to the health of ecosystems by cycling nutrients, promoting plant growth, and influencing the dynamics of entire communities. Studying these microbial processes helps us develop strategies for environmental conservation and restoration.
5. Industrial Applications: Microbes have immense potential for industrial applications. They are used in biotechnology to produce enzymes, antibiotics, biofuels, and other valuable compounds. Microbes can also be engineered for various purposes, including the production of pharmaceuticals and the degradation of environmental pollutants. Understanding the fundamental biology of microbes and their metabolic pathways allows us to harness their capabilities for the development of sustainable and efficient industrial processes.

The Petri Dish as a Tool

The marvels of technology have brought us an array of tools that empower us to peer into this unseen universe. Nowadays, even a simple mobile phone can be transformed into a microscope-like device, revealing a whole new dimension to the objects around us.

However, in the realm of scientific research, the petri dish is an indispensable tool that has revolutionized the study of microbes. A petri dish is a shallow, cylindrical glass or plastic dish with a lid that creates a controlled environment for cultivating and studying microorganisms. The dish is filled with a solid jelly-like medium called agar, which provides essential nutrients for microbial growth.

The use of petri dishes and agar has significantly contributed to our understanding of microbes and their characteristics. Here are some key aspects highlighting the importance of the petri dish as a tool:

1. Cultivation of Microbes: Agar plates provide a suitable environment for the cultivation of microorganisms. Agar, derived from seaweed, is a jelly-like substance that is added to essential nutrients to form a medium that supports the growth of various types of bacteria, fungi, and other microorganisms on a solid or semi-solid surface. By inoculating the agar with a sample containing microorganisms, researchers can observe and study the colonies that develop over time.
2. Visualizing Microbial Diversity: The solid surface of the agar plate allows for the visual observation of microbial colonies that originated from a single cell. Each microorganism has distinct characteristics, such as color, shape, and texture, which can be observed when colonies grow on the agar surface. By examining these characteristics, scientists can identify and classify different types of microorganisms and study their behavior and properties.
3. Isolation and Pure Culture: Agar plates enable the isolation and cultivation of pure cultures of microorganisms. By streaking a sample across the agar surface, individual microbial cells can be separated and encouraged to form isolated colonies. Pure cultures are crucial for studying the characteristics and behaviors of specific microorganisms without interference from other organisms.
4. Experimental Manipulation: The petri dish allows for easy experimental manipulation and observation. Scientists can introduce different substances or environmental factors with the organisms growing on the agar plates and observe the resulting effects on microbial growth and behavior. This versatility enables researchers to investigate specific hypotheses, test new treatments, and explore the underlying mechanisms of microbial processes.

In this step-by-step activity, provided by Dr. Sandra Wilks during a Joyful Microbe podcast episode, you will learn how to create your own agar plates. By growing colonies of microbes from various sources, you’ll embark on a journey of exploration, witnessing the diverse shapes, sizes, and colors that these microbes can exhibit.

Create Your Own Agar Plates

Materials:

• 3-4 Medium-sized potatoes
• Large pot (for boiling potatoes)
• Canning jar (with lid)
• Sugar
• Unflavored gelatin, gelatin strips, or agar
• Petri dishes
• Rainwater (preferred) or tap water
• Soil sample

Instructions:

1. Cut and boil Potatoes: Cut the potatoes into small cubes. Cover with water and boil the potatoes until the water has become a light brown color (20-30 minutes). Once boiled, carefully strain the potatoes, separating the water from the potatoes themselves, keeping the potato water.
2. Prepare the Agar Mixture: Cool the potato water until sill warm. Take a canning jar and pour the potato water into it. To the potato water, add 1/4 cup of sugar and include a substance that will help the mixture solidify into a jelly-like consistency. You can choose between a packet of unflavored gelatin, a couple of gelatin strips, or 1 tablespoon of agar. Note: you may need to practice and try different amounts to get the right consistency.
3. Sterilize the Agar Mixture: Securely close the canning jar with its lid and place it in a large pan of boiling water. Let it boil for at least 20 minutes to ensure complete sterilization of the mixture. Exercise caution while handling boiling water to avoid accidents.
4. Cool the agar slightly: Remove from the water (take care because it will be very hot) and then carefully remove the lid but leave it covering the jar so no unexpected bacteria or fungi can get in!
5. Pour the Agar: Once it has cooled a little bit, carefully pour the agar mixture into the petri dishes and place the lids on. Allow the gel to solidify. Then, store the plates with the lid facing down (to prevent condensation from falling on agar) wrapped in food wrap or plastic bags in the refrigerator until use to prevent them from drying out.
6. Collect Samples: Now comes the exciting part—collecting samples from the environment. You can take a small amount of soil and mix it with a bit of rainwater. Alternatively, you can use tap water, although it may require a longer incubation period.
7. Inoculate the plates: Gently spread the soil or water sample onto the solidified agar surface by tilting the petri dish. To add a personal touch, you can also press your thumb, finger, or even your entire hand onto one of the petri dishes. You can also take samples with Q-tips and swab across the plate.
8. Incubation Period: Cover the container with its lid, put tape around the outside to keep the lid on, turn it upside down (agar side up and lid facing down), and place it in a warm location, preferably around room temperature. Allow the agar plates to incubate undisturbed for a few days, monitoring their progress.
9. Witness the Microbial Colonies: After the incubation period, take a look at your plates (keeping the lids on), and prepare to be amazed. You will likely discover an array of colorful and distinct colonies of bacteria. Observe their varied sizes, shapes, and hues. Remember that finding microbes on these surfaces is normal and expected.

Safety precautions: Keep the lids on the petri dishes after microbial growth to avoid exposure to any harmful microbes. At low levels, they may not be harmful, but at higher numbers, after growing on a petri dish, they can become more of a risk. And after finishing, double-bag your petri dishes before placing them in the trash.

Exploring the world that surrounds us can be an eye-opening experience. Remember, it’s perfectly normal to find various microorganisms on these surfaces or samples. Embrace this opportunity to witness the diverse array of colonies that may emerge, each with its unique sizes, colors, and characteristics. It’s a chance to gain insight into the unseen world that coexists with us every day.

Observing the Beauty and Intricacy of Microbial Life

Creating your own agar plates and observing the growth of microbial colonies is a fascinating way to explore the hidden world of microorganisms. By following these step-by-step instructions, you can embark on a journey of discovery, witnessing the diversity and complexity of the microbial realm. This activity not only provides a glimpse into the beauty of microbes but also encourages a deeper understanding and appreciation of the essential role they play in our daily lives. So, grab some potatoes and get ready to uncover the fascinating wildlife documentary unfolding right before your eyes.