Bacteria Bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of 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 portions of Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only about half of the
Gasteroid fungi described by Linnaeus in his original "Species Plantarum" of 1753, but the first critical treatment of the group was by Christiaan Hendrik Persoon in his "Synopsis methodica fungorum" of 1801. Until 1981, this book was the starting point for the naming of Gasteromycetes under the "International Code of Nomenclature for algae, fungi, and plants". Although the starting point was subsequently put back to 1753, names of gasteroid fungi used in Persoon's book are still sanctioned and cannot be replaced by earlier names. Elias Magnus Fries introduced the name Gasteromycetes for a class of fungi in his "Systema Mycologicum" of 1821,