Bacteria

Tiny living things are everywhere.

They live in soil and water. They even live in hot springs.

Some live on your skin. Most are good for us. They help make food. They also help clean up waste. Some can make you sick. But most stay helpful. These tiny things are very important to our world.

Bacteria are tiny living things. Most are made of just one cell.

They were some of the first life forms on Earth. They live almost everywhere. You can find them in soil and water. They live in hot springs and deep in the Earth. They even live in space!

Bacteria have many shapes. Some are round. We call these cocci. Others look like sticks. We call these bacilli.

Some are shaped like spirals. These shapes help them find food. They also help them move and stay safe.

Most bacteria are helpful. They help recycle nutrients in nature. They help make food like cheese and yogurt. They even help clean up oil spills. Humans carry many bacteria. Most live in our gut. Most are harmless or even good for us. However, some bacteria are pathogenic. This means they can cause disease. They can cause things like cholera or tetanus. We use antibiotics to treat these sicknesses.

Bacteria are tiny living things that are found almost everywhere on Earth. Most bacteria are made of just one single cell. They belong to a large group of microscopic life called prokaryotes. This means their cells are built differently than ours. For example, they do not have a nucleus to hold their genetic material. They also lack most of the small, enclosed parts found in animal cells.

Scientists who study these tiny life forms are called bacteriologists. This is a special branch of microbiology. Even though they are small, they are very important to our world.

These tiny cells work in many important ways to keep nature healthy. Bacteria help with the nutrient cycle by recycling things like dead bodies. This stage of breaking things down is called putrefaction. Some bacteria even help by taking nitrogen from the air and fixing it into the soil. In the deep ocean, special bacteria called extremophiles live near hot vents. They turn things like methane into energy to support other life.

Without these small workers, many parts of our planet would not function. They even help clean up oil spills and treat sewage.

Life on Earth has a very long history with bacteria. They were among the very first living things to appear about 4 billion years ago. For a long time, they were the main form of life on our planet. Scientists believe that much later, ancient bacteria entered into partnerships with other cells. This helped create the complex cells that make up plants and animals.

This process is known as endosymbiosis. It is how some cells gained parts like mitochondria. This deep history shows how closely we are linked to them.

Bacteria come in many different shapes and sizes. Most are only about 0.5 to 5.0 micrometres long. However, some species like Thiomargarita magnifica can grow up to 2 centimeters!

You might see them as round spheres called cocci. Others look like sticks and are called bacilli. Some are shaped like spirals, which are called spirilla or spirochaetes.

These shapes help them find food and move through liquids. They can also live alone or group together in thick layers called biofilms.

Humans live with bacteria every single day. We carry trillions of them on our skin and in our guts.

Most of these are helpful or harmless to us. Some bacteria in our gut actually help us stay healthy. However, some types are pathogenic, which means they cause diseases. These can cause illnesses like cholera, tetanus, or the bubonic plague.

We use medicines called antibiotics to fight these infections. We even use bacteria to make tasty foods like yogurt and cheese through fermentation.

Bacteria are ubiquitous, single-celled microorganisms that belong to the domain of prokaryotes. They are among the most successful life forms on Earth, appearing about 4 billion years ago. These organisms are found in almost every habitat imaginable. They thrive in soil, water, and the air. Some even live in extreme environments like acidic hot springs or radioactive waste.

Bacteria are essential to the planet's survival. They drive the nutrient cycle by recycling dead matter through a process called putrefaction. They also perform nitrogen fixation, which moves nitrogen from the atmosphere into the soil.

At a cellular level, bacteria are structurally distinct from eukaryotes, which include plants and animals. A bacterial cell is surrounded by a cell membrane made of phospholipids. This membrane acts as a barrier to protect essential proteins and nutrients. Unlike eukaryotic cells, bacteria do not have a nucleus to house their genetic material. Instead, they contain circular chromosomes. They also lack membrane-bound organelles, which are the specialized internal compartments found in larger cells.

This simple structure allows them to remain efficient and highly adaptable.

Bacteria display a massive variety of shapes and arrangements. Most species are categorized by their physical form. Spherical bacteria are called cocci, while rod-shaped bacteria are known as bacilli. Some appear as curved rods called vibrio, or as spirals known as spirilla and spirochaetes.

These shapes are determined by the cell wall and the cytoskeleton. The specific shape helps a bacterium acquire nutrients or escape from predators. While most are microscopic, some are surprisingly large. For example, *Thiomargarita magnifica* can reach 2 centimeters in length. This is 50 times larger than typical bacteria.

Bacteria do not always live as solitary cells. Many species form complex groups or patterns. Some form pairs called diploids, while others form long chains or grape-like clusters. Certain bacteria, such as myxobacteria, use a process called quorum sensing to communicate. When they sense they are starving, they migrate together to form fruiting bodies. These structures can contain up to 100,000 cells that perform different tasks.

Many bacteria also create biofilms. A biofilm is a dense aggregation of cells attached to a surface. These can grow up to half a meter deep. Biofilms protect bacteria, making them much harder to kill with medicine.

Historically, our understanding of bacteria has changed significantly. In the past, scientists incorrectly classified them as plants called Schizomycetes. We now know they are prokaryotes. In the 1990s, researchers discovered that prokaryotes actually consist of two distinct groups. These are the domains Bacteria and Archaea. While they look similar, they have deep genetic differences. For example, bacteria use ester-linked lipids in their membranes. They also use formylmethionine to start protein synthesis.

Humanity has a complex relationship with these organisms. Humans carry between 10^13 and 10^14 bacteria on and in their bodies. Most of these live in the gut and are either harmless or beneficial. However, some bacteria are pathogenic, meaning they cause infectious diseases. These include cholera, anthrax, tuberculosis, and the bubonic plague.

To fight these, we use antibiotics. However, the use of antibiotics in medicine and farming has led to the rise of antibiotic resistance.

Beyond health, bacteria are vital to global industry and ecology. They are used in sewage treatment and the breakdown of oil spills. In the food industry, fermentation by bacteria produces cheese and yogurt. In mining, a process called biomining uses bacteria to recover metals like gold and copper. They even help provide oxygen; bacteria in the oceans provide up to 50% of the oxygen humans breathe.

Despite their importance, we have only fully studied about 2% of all bacterial species. Much of the microbial world remains a vast, unexplored frontier.