Microorganisms

A bacteriophage is a virus that infects bacteria. Some phages can destroy specific bacterial species and are being studied as alternatives to antibiotics.

A biofilm is a community of microorganisms attached to a surface and surrounded by a protective slimy matrix. Biofilms can form on teeth, rocks, pipes, and medical devices.

Quorum sensing is a chemical communication system bacteria use to detect their own population density. It helps them coordinate behavior such as biofilm formation and toxin production.

A plasmid is a small circular DNA molecule found in many bacteria, separate from the main chromosome. Plasmids often carry useful genes such as antibiotic resistance.

Horizontal gene transfer is the movement of genes between organisms without parent-to-offspring inheritance. In bacteria, it helps spread traits like antibiotic resistance very quickly.

Conjugation is a form of gene transfer in which one bacterium passes DNA to another through direct contact. It often involves a plasmid and a structure called a pilus.

Transformation is the uptake of free DNA from the environment by a bacterium. Some bacteria can use this DNA to gain new traits.

Transduction is gene transfer between bacteria mediated by a bacteriophage. A virus accidentally carries bacterial DNA from one cell to another.

A gram stain is a laboratory test that classifies bacteria as Gram-positive or Gram-negative based on their cell wall structure. It remains one of microbiology’s most basic diagnostic methods.

Peptidoglycan is a strong mesh-like molecule that forms much of bacterial cell walls. It helps bacteria keep their shape and resist bursting.

An extremophile microbe is a microorganism that thrives in extreme conditions such as high heat, high salt, acidity, or radiation. Many are archaea, but some bacteria also qualify.

An endospore is a dormant, highly resistant structure formed by certain bacteria. It helps them survive heat, drying, chemicals, and time.

A prebiotic is a type of food ingredient that nourishes beneficial microbes, especially in the gut. Unlike probiotics, prebiotics are not live organisms.

A microbiome is the community of microorganisms living in a particular environment, such as the human gut, soil, or ocean. It also often refers to the collective genetic material of those microbes.

A zoonotic bacterium is a bacterium that can spread from animals to humans. Examples include Salmonella and some strains of Campylobacter.

Antibiotic resistance is the ability of bacteria to survive drugs that once killed them or stopped their growth. It makes infections harder to treat and can lead to longer illness or more serious outcomes.

A superbug is a bacterium that is resistant to multiple antibiotics. The term is commonly used for hard-to-treat infections such as MRSA.

A pathogen is a microorganism that causes disease. Pathogens can be bacteria, viruses, fungi, or parasites.

A gut bacterium is a bacterium that lives in the digestive tract, especially the intestines. Many gut bacteria help break down food and support the immune system.

A bacterial colony is a visible cluster of bacteria growing from a single cell or a small group of cells on a solid surface. Colonies can differ in size, shape, color, and texture.

A bacterial flagellum is a whip-like structure used for movement. It helps some bacteria swim through liquid or move toward nutrients.

Chemotaxis is movement in response to chemical signals. Bacteria use it to move toward nutrients or away from harmful substances.

A nitrogen-fixing bacterium converts nitrogen gas from the air into forms that plants can use. This process is essential for soil fertility and agriculture.

A cyanobacterium is a photosynthetic bacterium that uses sunlight to make energy. Cyanobacteria helped produce much of Earth’s oxygen billions of years ago.

A bacterial capsule is a protective outer layer outside the cell wall of some bacteria. It can help them evade the immune system and resist drying out.

A microbiologist is a scientist who studies microorganisms such as bacteria, viruses, fungi, and protozoa. They work in medicine, food safety, ecology, and biotechnology.

A bacterium is a single-celled microorganism with no true nucleus. Bacteria are found almost everywhere on Earth and can be helpful, harmless, or harmful.