Eubacteria

Eubacteria The domain that comprises the single kingdom Bacteria, containing the true bacteria. There are 11 main groups: purple (photosynthetic), Gram-positive, cyanobacteria, green non-sulphur, spirochaetes, flavobacteria, green sulphur, Planctomyces, Chlamydiales, Deinococci, and Thermatogales. The only feature common to all bacteria is their prokaryotic cellular organization. The majority of bacteria are single-celled, and most have a rigid cell wall. Cell division usually occurs by binary fission; mitosis never occurs. Bacteria are almost universal in distribution and may live as saprotrophs, parasites, symbionts, pathogens, etc. They have many important roles in nature, e.g. as agents of decayed and mineralization, and in the recycling of elements (such as nitrogen) in the biosphere. Bacteria are also important to humans, e.g. as causal agents of certain diseases, as agents of spoilage of food and other commodities, and as useful agents in the industrial production of commodities such as vinegar, antibiotics, and many types of dairy product. The oldest fossils known are of bacteria, from rocks in S. Africa that are apparently 3200 million years old. These must have been heterotrophic bacteria, feeding off organic molecules dissolved in the oceans of that time. The first photosynthetic bacteria, of anaerobic type, appeared a little later, about 3000 Ma ago.