Useful and Dangerous Microorganisms
Problematic — How can microorganisms be both useful to humans and sometimes dangerous to health?
- Understand what a microorganism is.
- Identify different types of microorganisms.
- Discover that some microorganisms are useful in food, the environment, or the human body.
- Understand that some microorganisms can be dangerous.
- Learn simple actions to limit the transmission of pathogenic microorganisms.
Part 1: Discovering the World of Microorganisms
A microorganism is a microscopic living being, too small to be seen with the naked eye. Some microscopic agents, like viruses, are not considered living beings but can also cause diseases.
Microorganisms are present almost everywhere: in the air, water, soil, on our skin, in our mouth, in our intestines, on food, and on objects we touch.
They are very diverse. Some are living beings, such as bacteria, yeasts, or certain molds. Others, like viruses, need a living cell to reproduce.
The microscope is an instrument that allows observation of elements too small to be seen with the naked eye.
Some Major Types of Microorganisms
| Type | What it is | Simple Example |
|---|---|---|
| Bacteria | Microorganisms made up of a single cell. | Some bacteria turn milk into yogurt. |
| Yeasts | Microscopic fungi made up of a single cell. | Baker's yeast makes bread dough rise. |
| Molds | Microscopic fungi that sometimes form visible filaments. | Mold can grow on a forgotten piece of fruit. |
| Viruses | Microscopic agents that multiply inside living cells. | Some viruses can cause illnesses such as the flu. |
A drop of water from a pond may contain many microorganisms. They are invisible to the naked eye, but some can be seen under a microscope.
Microorganisms are microscopic living beings present in many environments. Viruses are special microscopic agents: they are not considered living microorganisms in the same sense as bacteria, yeasts, or molds, but they can cause diseases. They are too small to be seen with the naked eye. We can distinguish several major types, such as bacteria, yeasts, and molds. Viruses are particular microscopic agents that need a living cell to multiply. Microorganisms and viruses are very numerous around us and in our bodies.
Part 2: Useful Microorganisms
Not all microorganisms are dangerous. Many are useful, and some are even essential in our daily lives, in our food, in our body, and in natural environments.
A useful microorganism is one that provides a service to humans, other living beings, or to the functioning of an environment.
Useful Microorganisms in Food
Some microorganisms transform foods. This transformation can change the taste, texture, smell, or preservation of food. This process is often called fermentation.
Fermentation is a transformation of matter carried out by certain microorganisms. It is used to produce some foods.
| Food | Microorganism used | Transformation performed |
|---|---|---|
| Yogurt | Lactic bacteria | They transform milk and give yogurt its texture. |
| Bread | Baker's yeast | It produces carbon dioxide, a gas that makes the dough rise. |
| Cheese | Bacteria and sometimes molds | They contribute to taste, texture, and aging. |
In bread dough, yeasts use certain sugars present in the dough. They produce carbon dioxide, which forms bubbles and makes the dough rise.
Useful Microorganisms in Our Body
Our body hosts many microorganisms. Many live on our skin, in our mouth, or in our intestines. Some help protect our body or assist in digestion.
The microbiota is the set of microorganisms that naturally live in or on an organism, for example in the intestine or on the skin.
The intestinal microbiota contributes to proper digestion functioning. It can also help limit the growth of some dangerous microorganisms.
Useful Microorganisms in the Environment
In nature, some microorganisms transform dead matter, like fallen leaves, animal remains, or organic waste. They participate in recycling matter.
In soil, certain bacteria and fungi help transform dead leaves. This transformed matter can then enrich the soil.
Many microorganisms are useful. Some help produce foods like yogurt, bread, or cheese. Others live in our body and contribute to its proper functioning, like the microorganisms in the intestinal microbiota. In the environment, some microorganisms take part in transforming and recycling dead matter.
Part 3: Sometimes Dangerous Microorganisms
Some microorganisms can be dangerous when they enter the body and multiply. They can cause diseases. These are called pathogenic microorganisms. Some viruses can also cause diseases.
A pathogenic microorganism is one capable of causing disease in a living being. By extension, viruses are also called pathogens.
How Can Pathogens Enter the Body?
Pathogenic microorganisms and viruses can enter the body through different routes. They can pass through the mouth, nose, eyes, a wound, or sometimes be transmitted by an animal.
| Possible Entry Route | Common Situation | Precaution Example |
|---|---|---|
| Mouth | Eating contaminated food or touching the mouth with dirty hands. | Wash hands and properly store food. |
| Nose and mouth | Breathing droplets expelled during coughing or sneezing. | Cough into your elbow and ventilate rooms. |
| Wound | Pathogens can enter through a poorly cleaned cut. | Clean and protect the wound. |
| Eyes | Rubbing eyes with contaminated hands. | Avoid touching the face with dirty hands. |
If a sick person coughs into their hand then touches a door handle, pathogens may be on that handle. Another person can then pick them up on their hands by touching the same handle.
Infection and Disease
When a pathogenic microorganism enters the body and multiplies, it can cause an infection. The body reacts to defend itself. This reaction can be accompanied by symptoms like fever, fatigue, pain, cough, or digestive troubles.
An infection is the entry and multiplication of a pathogen in the body, for example a pathogenic bacterium or virus.
Not all microorganisms should be confused with harmful microbes. The word microbe is often used in everyday language to talk about microorganisms and viruses, but not all cause diseases.
Some microorganisms are dangerous because they can cause diseases: these are called pathogenic microorganisms. Some viruses can also cause diseases. These pathogens can enter the body through the mouth, nose, eyes, or a wound. When they multiply inside the body, they can cause infections and trigger symptoms.
Part 4: Reducing Risks and Using Microorganisms Carefully
Since some microorganisms and viruses can be dangerous, it is important to adopt simple habits to limit their transmission. These habits are part of hygiene.
Hygiene refers to all the actions that help reduce contamination risks and protect health.
Everyday Hygiene Habits
Hygiene habits reduce the number of pathogens on hands, objects, food, or in the air.
- Wash your hands with water and soap, especially before eating and after using the toilet.
- Cough or sneeze into your elbow to avoid spreading droplets around you.
- Regularly air out rooms to renew the air.
- Clean and protect wounds with an appropriate bandage.
- Follow food storage rules, like keeping some foods refrigerated.
- Avoid consuming food that smells, looks, or has unusual mold.
Hand washing removes some microorganisms on the skin. It’s a simple yet very effective action to limit the transmission of many pathogens.
Food Storage to Limit Contamination
Microorganisms develop more easily in certain conditions, especially when food is left too long at room temperature. Cold often slows their multiplication but does not always destroy microorganisms.
| Method | Main Effect | Example |
|---|---|---|
| Refrigeration | Slows down the development of many microorganisms. | Keep yogurt or meat in the refrigerator. |
| Cooking | Destroys many harmful microorganisms. | Cook certain foods thoroughly before eating. |
| Washing fruits and vegetables | Removes some dirt and microorganisms on the surface. | Rinse an apple before eating it. |
| Clean packaging | Limits contact with external microorganisms. | Keep food in a closed container. |
Using microorganisms requires knowing how to distinguish useful situations from risky ones. A microorganism can be helpful in one context but dangerous in another if it contaminates food, a wound, or the body.
Hygiene habits help limit the transmission of pathogens. Hand washing, airing rooms, protecting wounds, and proper food storage are simple and effective actions. Microorganisms can be useful, but some situations require caution to avoid contamination and protect health.
Microorganisms are microscopic living beings found almost everywhere around us and in our bodies. They can be bacteria, yeasts, or molds. Viruses are special microscopic agents that need a living cell to multiply. Many microorganisms are useful: some help produce foods like bread, yogurt, or cheese; some contribute to the proper functioning of our microbiota; and others transform dead matter in the environment. However, some microorganisms are pathogenic and can cause diseases when they enter the body and multiply. Simple hygiene actions, such as washing hands, protecting wounds, airing rooms, and properly storing food, help limit the risk of contamination.