Microbiology Demonstrations

See also: Cells and Microscopes

Microbiology is the study of organisms too small to be seen with the naked eye, including bacteria, viruses, fungi, and protozoa. This category introduces their structures, roles in ecosystems, and impacts on health and industry. Understanding microbiology connects biology to medicine, food science, and environmental studies.

Demonstration	Materials	Difficulty	Safety	Summary
Luminous Powder Germ Spread	★★★	★☆☆	★☆☆	A fluorescent or luminous powder is used with UV light to show how germs spread and to reveal areas of the hands that are often missed during handwashing. The demonstration highlights the importance of thorough cleaning for preventing contamination.
Aerobic vs. Anaerobic Yeast Respiration	★★☆	★☆☆	★☆☆	This experiment demonstrates yeast respiration by placing yeast, sugar, and warm water in bottles sealed with balloons. Under aerobic conditions, yeast uses oxygen to produce carbon dioxide rapidly, inflating the balloon more. Under anaerobic conditions, yeast ferments sugar into ethanol and carbon dioxide, inflating the balloon more slowly.
Culturing Bacteria	★★☆	★☆☆	★★☆	Students grow bacteria on nutrient agar in Petri dishes by swabbing everyday surfaces and observing colony growth. The activity demonstrates the presence of microbes all around us and can be extended into a science fair project by testing antibacterial products.
Exploring Pond Water with a Microscope	★★☆	★☆☆	★★☆	Students collect pond water samples and prepare microscope slides to observe microorganisms such as algae, protozoa, rotifers, and tiny crustaceans. The activity demonstrates biodiversity and introduces microscopy techniques for studying aquatic ecosystems.
Gram Staining	★★☆	★☆☆	★★☆	Gram staining is a widely used technique in microbiology to distinguish between Gram-positive and Gram-negative bacteria. By applying a series of stains and washes, students observe differences in bacterial cell walls that cause some cells to appear purple (Gram-positive) and others pink (Gram-negative) under the microscope.
Laser Microscope	★★☆	★★☆	★★☆	A laser is focused through a water droplet at the tip of a syringe, which acts as a convex lens. The light is projected onto a screen, allowing small aquatic organisms and impurities in the water to be observed.
Observing Yogurt Bacteria	★★☆	★☆☆	★★☆	Students prepare microscope slides of live yogurt cultures to observe probiotic bacteria such as Lactobacillus and Streptococcus.
Watching Yeast Make Bubbles	★★☆	★★☆	★☆☆	This demonstration shows how bread yeast ferments sugar to release carbon dioxide, which can inflate a balloon, and allows students to observe live yeast cells under a microscope.
Winogradsky Column	★★☆	★★☆	★★☆	A Winogradsky column is a simple way to grow diverse microbes from mud in a transparent container. Over several weeks, microbes form colorful layers that reveal differences in metabolism, oxygen tolerance, and nutrient use, providing a living model of microbial communities.
Making Yogurt	★☆☆	★★☆	★★☆	Students heat and cool milk, add a starter containing live bacterial cultures, and allow the mixture to incubate in a warm environment. Over several hours, the bacteria ferment lactose into lactic acid, thickening the milk and producing yogurt.
Mold Growth on Bread	★☆☆	★☆☆	★★☆	Students test how moisture affects mold growth on bread by comparing a dry slice with a moistened slice stored in sealed bags. Over time, they observe and record fungal growth, learning about decomposition and environmental factors influencing microbes.
Yeast and Bread Fermentation	★☆☆	★☆☆	★☆☆	Students explore the role of yeast in bread making by preparing dough in a bag, observing changes over time, and investigating how yeast fermentation produces carbon dioxide that causes dough to rise.
Yeast Fermentation	★☆☆	★☆☆	★☆☆	Students investigate how different sugars (white sugar, brown sugar, and honey) affect the rate of yeast fermentation by measuring the amount of carbon dioxide produced, observed through balloon inflation.

Materials
★☆☆ Easy to get from supermarket or hardware store
★★☆ Available in most school laboratories or specialist stores
★★★ Requires materials not commonly found in school laboratories

Difficulty
★☆☆ Can be easily done by most teenagers
★★☆ Available in most school laboratories or specialist stores
★★★ Requires a more experienced teacher

Safety
★☆☆ Minimal safety procedures required
★★☆ Some safety precautions required to perform safely
★★★ Only to be attempted with adequate safety procedures and trained staff