Class 1

 Bacteria and archaea are single-celled organisms without a nucleus, also known as prokaryotes . Their genetic material (DNA) is not enclosed in a nucleus. These microbes have been on Earth for billions of years and are found almost everywhere. Bacteria are extremely diverse and have adapted to nearly all environments on the planet . Archaea and bacteria look similar under a microscope, but archaea have some features more like eukaryotes – for example, the way their proteins and DNA processes work is closer to human cells .

Eukaryotes (Cells with a Nucleus)

Eukaryotes are organisms whose cells contain a nucleus to hold their DNA . These cells are usually larger and more complex than prokaryotic cells. Eukaryotes may be unicellular (single-celled) or multicellular . For instance, yeast is a single-celled eukaryote, while humans, plants, and animals are made of many eukaryotic cells working together.

Viruses (Not Living Cells)

Viruses are much smaller than bacteria and are not considered living cells. A virus is basically genetic material inside a protein coat. Viruses cannot reproduce or survive on their own – they must infect a living host cell to make more copies of themselves . Because they are not made of cells and cannot carry out life processes independently, scientists generally do not classify viruses as alive.

Ways Microbes Get Energy

Microbes (especially bacteria and archaea) have many different ways to get energy for living and growing. For example:

• Organic Food: Some microbes break down organic materials like sugars, plants, or animals for energy (similar to how we eat food).
• Inorganic Sources: Some microbes can use inorganic substances (like iron, sulfur, or other minerals) as an energy source .
• Making Their Own Food: Some microbes can use sunlight or chemical reactions to turn carbon dioxide into their own nutrients (like plants do with photosynthesis). These microbes, called autotrophs, make their own food from CO₂ and energy from light or chemicals.

Helpful Microbes in Our Bodies

Many microbes are beneficial and help keep us healthy. Here are some ways good microbes work in our bodies:

• Digestion (Gut): In our intestines, trillions of bacteria help break down food that we otherwise couldn’t digest. They even produce certain vitamins and nutrients for us . A healthy gut microbial community helps us absorb nutrients from food.
• Protection (Skin): The bacteria on our skin form a protective barrier. They protect us against pathogens (harmful germs) by crowding them out and producing substances that stop bad bacteria from growing . These good bacteria also help keep the skin’s pH (acidity) at a level that is unfriendly to dangerous microbes .
• Mouth Health: In the mouth, good microbes help start the digestion of food and keep the environment balanced. They help regulate pH levels in your mouth, preventing it from becoming too acidic . By doing so, they protect against tooth decay and gum disease (since extremely acidic conditions can damage teeth).

Microbes in Food and Industry

Humans use microbes to make food and medicine. For example, fermented foods like yogurt, kimchi, and cheese are made using helpful bacteria (or yeast). Eating these foods can add good bacteria to our gut and support a healthy microbiome . Fermented foods are associated with improved gut health and are one way we get “probiotics” (beneficial microbes) into our bodies.

Yeast, which is a type of fungus (and a eukaryotic microbe), is used to bake bread and brew beer through fermentation. In bread, yeast produces gas that makes the dough rise, and in beer, yeast produces alcohol. Microbes are also important in biotechnology and medicine – for instance, scientists can use genetically engineered bacteria or yeast to produce human insulin for diabetes treatment . This means we harness microbes to make vital medications and other useful products.

The Gut Microbiome and Health

The community of microbes living in our digestive system is called the gut microbiome. A healthy gut microbiome helps fight disease by supporting our immune system and preventing the overgrowth of harmful bacteria . In fact, the beneficial gut bacteria teach our immune cells and keep harmful microbes in check, which protects us from infections. Scientists have also discovered that the gut microbiome is linked to our mood and brain health . The brain and the gut communicate constantly, and changes in gut bacteria have been connected to changes in mood, stress levels, and conditions like anxiety or depression. In summary, having a balanced, healthy set of microbes (microbiome) in our body is important for overall health, affecting everything from digestion and immunity to even mental well-being.