Discover the microscopic organisms and particles that shape ecosystems, health, food, and life on Earth.
Microbiology is the study of organisms and biological agents too small to see clearly without magnification. Microbes live almost everywhere, including soil, water, air, plants, animals, and the human body. Some cause disease, but many others recycle nutrients, help digest food, produce useful substances, and support entire ecosystems.
Single-celled organisms with enormous variety in shape, metabolism, and habitat.
Learn MoreMicrobes that may resemble bacteria but differ in important genetic and chemical ways.
Learn MoreMicroscopic yeasts, molds, algae, and protozoa fill many ecological roles.
Learn MoreGenetic material inside protective particles that reproduce only within host cells.
Learn MoreCommunities of microbes interact with one another and with larger organisms.
Learn MoreMicroscopes, cultures, stains, sequencing, and other methods reveal the microbial world.
Learn MoreBacteria are single-celled organisms that lack a membrane-bound nucleus. They can be shaped like spheres, rods, spirals, or other forms, and they obtain energy in many different ways. Some bacteria break down dead material, some help plants obtain nutrients, and some live harmlessly or beneficially in animal bodies. A smaller number can cause disease when they enter tissues, produce toxins, or multiply where they do not belong.
Archaea are also single-celled microorganisms without a nucleus, but their cell chemistry and genetics differ from those of bacteria. Some species live in very salty, hot, acidic, or oxygen-poor environments, while many others occur in ordinary oceans, soils, sediments, and animal digestive systems. Studying archaea has helped scientists understand the diversity of life and the deep evolutionary relationships among living organisms.
Many fungi and protists are microscopic. Yeasts are single-celled fungi used in baking and fermentation, while molds grow as networks of filaments and play major roles in decomposition. Protists include many algae and protozoa with very different lifestyles. Some photosynthetic protists form the base of aquatic food webs, while others consume bacteria or other tiny organisms.
Viruses are not cells. They contain genetic material, usually DNA or RNA, surrounded by a protein coat and sometimes an outer membrane. A virus cannot reproduce independently; it must enter a suitable host cell and use that cell's machinery to make new virus particles. Viruses infect animals, plants, fungi, bacteria, and archaea, making them important parts of both disease research and ecosystem science.
A microbiome is a community of microorganisms living in a particular environment. Human skin, intestines, plant roots, lake water, and forest soils all support complex microbial communities. These microbes can compete, cooperate, exchange nutrients, and influence larger organisms around them. Scientists study microbiomes to understand digestion, agriculture, disease, nutrient cycling, and the stability of ecosystems.
Because microbes are so small, microbiologists rely on specialized tools. Light and electron microscopes reveal structures at different scales, while stains can make cells easier to distinguish. Researchers may grow microbes in controlled cultures, test how they respond to nutrients or medicines, and analyze DNA to identify organisms that are difficult to grow. Combining these methods gives scientists a more complete picture of microbial life.