Microscopic organism which may have a spherical, rod-like, or spiral unicellular or non-cellular body. Bacteria usually reproduce through asexual processes.
All bacteria consist of a single cell surrounded by a cell wall; DNA is circular; bacteria do not have internal membrane systems.
A microscopic organism. Some types are permanently present in the gut and can break down food tissue, but many can cause disease.
Bacteria, any of a large group of small, unicellular microorganisms (class Schizomycetes) found in the soil, water, and air, some of which cause disease in humans and other animals. Bacteria are generally classified as rod-shaped (bacillus), spherical (coccus), comma-shaped (vibrio), or spiral (spirochete).
A one-celled organism without a true nucleus or cell organelles, belonging to the kingdom Procaryotae (Monera). The cytoplasm is surrounded by a rigid cell wall composed of carbohydrates and other chemicals that provide the basis for the Gram stain. Some bacteria produce a polysaccharide or polypeptide capsule, which inhibits phagocytosis by white blood cells. Bacteria synthesize DNA, RNA, and proteins, and they can reproduce independently but may need a host to provide food and a favorable environment. Millions of nonpathogenic bacteria live on human skin and mucous membranes; these are called normal flora. Bacteria that cause disease are called pathogens.
A unicellular microorganism that is visible only under a microscope. Numerous bacteria are capable of causing diseases.