Microbes
An estimated 10 million species of bacteria live on the Earth. These, and other microbes, make up a large part of the planet’s living material. Microbes thrive on land, in the oceans and on human skin. They even survive in extreme places like near deep-sea vents. People often think of microbes as just causing diseases — such as fungal infections in plants or pneumonia in humans. In spite of their bad reputation, microbes also play important roles in Earth’s ecosystems. For example, bacteria living in the ocean produce half of the oxygen in the atmosphere. Without them, we couldn’t breathe.
Even before the invention of the microscope, people noticed the effects of microbes on human health. Microscopes and other tools, however, enabled people to study these unseen creatures directly. Early on, scientists simply observed microbes. Later they began to understand how microbes live, grow and cause disease. This knowledge enabled scientists to develop ways to fight and prevent diseases caused by microbes. Scientists can also use microbes for many other applications, such as creating better food and new sources of energy.
Microscopic Worlds
Microbes are extremely small, and can only be seen with a microscope. They are smaller than a human red blood cell. Millions of microbes can fit inside the eye of a needle. They are also very old. In fact, they are the oldest form of life on Earth. They roamed the Earth — in their own microscopic way — hundreds of millions of years before the dinosaurs. They live everywhere. Dig up the soil, and you will find countless microbes living there. Take a sample of air, and they are there as well. They even live inside our digestive systems.
The many species of microbes can be organized in several ways. Familiar categories include the bacteria, fungi, and viruses. There are even microscopic animals — such as dust mites — which resemble tiny insects. Microbes can also be split into two groups based upon whether they have a cell nucleus. This membrane-bound part of the cell encloses the genetic material. In addition, microbes can be classified by how they obtain and process their food. Or how they react to oxygen. Some microbes need oxygen to survive. Others — like the ones living inside our digestive system — are killed by oxygen.
Importance of Microbes
Microbes are essential components of every ecosystem. They produce the oxygen that we need to live. They break down garbage and dead organisms. They produce nutrients that plants need to grow. They even help us digest our food. In addition to these natural activities, microbes are needed for making foods like bread, wine and beer. Scientists also use microbes for practical applications. Microbes at a sewer treatment plant help breakdown the waste. Microbes can also be used to change the genetic composition of plants and animals. This gives them new traits, such as resistance to pesticides.
Microbes are probably better known for the diseases that they cause. AIDS, tuberculosis, bacterial meningitis and the common cold are all caused by microbes. Greater understanding of how microbes live and function, though, has enabled scientists to prevent and treat diseases. Vaccines, antibiotics and other drugs are powerful tools for reducing illnesses caused by microbes. Not all discoveries, however, were planned. Penicillin, an antibiotic produced by a fungus, was discovered largely by accident. In spite of the many scientific discoveries, washing and proper sanitation are still important tools in preventing diseases caused by microbes.