Bacterial Infectious Diseases
Bacteria common noun bacteria, singular bacterium is a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically, a few micrometers in length, bacteria have several shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of the earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals.