Back to: MICROBIOLOGY 200 LEVEL
Welcome to class!
Hello, brilliant mind! I’m so excited to learn with you today. Just like humans enjoy different kinds of food—some love amala and ewedu, others prefer rice and stew—microorganisms also have different “food preferences” and energy sources. They don’t all feed the same way. In today’s class, we’re going to learn about the Nutritional Types of microbes: phototrophs, chemotrophs, heterotrophs, and autotrophs. Get ready—it’s going to be simple, relatable, and fun!
Nutritional Types (Phototrophs, Chemotrophs, Heterotrophs, Autotrophs)
What Are Nutritional Types?
Nutritional types describe how microorganisms get their energy and what source they use to build their cells. Think of it this way: to live and grow, every microbe needs two things:
Energy source – something that gives them power.
Carbon source – something to build their body structures.
Now, based on these, microbes fall into different groups.
1. Phototrophs – The Light Lovers
These microbes get their energy from light, just like plants do. They use sunlight to make food through a process called photosynthesis.
Example: Cyanobacteria (found in ponds and moist soil).
Just like sunflowers need the sun to grow, phototrophs also rely on sunlight.
2. Chemotrophs – The Chemical Users
Instead of light, chemotrophs get their energy from chemicals. They break down compounds in their environment (like sugar, ammonia, or sulphur) to generate energy.
Example: Nitrosomonas (a soil bacterium that uses ammonia).
It’s like charging your phone using a generator instead of solar—still gets the job done, but differently.
3. Autotrophs – The Self-Feeders
Autotrophs use carbon dioxide (CO₂) as their carbon source. They don’t need to eat other organisms to survive—they make their own food, just like plants.
Can be either phototrophic (using light) or chemotrophic (using chemicals).
Example: Cyanobacteria (again!), which are photoautotrophs.
4. Heterotrophs – The Dependent Ones
These ones cannot make their own food. They get their carbon from organic compounds—basically, they “eat” other organisms or substances made by them.
Example: Most bacteria that cause diseases in humans.
Just like we depend on food from farms or markets, heterotrophs depend on ready-made organic nutrients.
Imagine students preparing for exams:
One studies using sunlight during the day (phototroph),
another uses a reading lamp powered by a generator (chemotroph).
One writes his own notes (autotroph),
another copies from friends (heterotroph).
Each one is learning in their own way—just like microbes survive in their own unique styles.
Summary
- Microbes are classified by how they get energy (light or chemicals) and carbon (CO₂ or organic compounds).
- Phototrophs use light; chemotrophs use chemicals.
- Autotrophs make their own food from CO₂; heterotrophs depend on external organic sources.
- Some microbes fall into combined categories like photoautotrophs or chemoheterotrophs.
Evaluation
- What is the difference between autotrophs and heterotrophs?
- Which type of microbe uses light as its energy source and CO₂ as its carbon source?
- Name one microorganism that is a chemoautotroph.
- In your own words, compare a photoheterotroph to a chemoheterotroph using a real-life example.
Well done, champ! You’re not just learning—you’re growing into a true microbiologist. Understanding how microbes feed gives you the power to understand nature better. With Afrilearn, learning is always exciting, personal, and made just for you. Keep believing in yourself—you’ve got what it takes to achieve greatness. See you in the