Are microorganisms always helpful to us? What are their harmful effects?

Explanation

### Step-by-Step Solution

1. **Understanding Microorganisms**: Microorganisms are tiny living organisms that can only be seen under a microscope. They include bacteria, viruses, fungi, and protozoa.

2. **Beneficial Microorganisms**: Not all microorganisms are harmful; many are beneficial. For example:
- **Gut Bacteria**: Certain bacteria in our intestines help in digestion and produce vitamins.
- **Fermentation**: Microorganisms like yeast are used in the production of bread, beer, and yogurt.

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