Bacteria came in 1977 when Carl Woese recognised that archaea have a separate line of evolutionary descent from bacteria. This new phylogenetic taxonomy depended on the sequencing of 16S ribosomal RNA, and divided prokaryotes into two evolutionary domains, as part of the three-domain system. 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
Social history of viruses are bacteria and archaea. Viruses are the main agents responsible for the rapid destruction of harmful algal blooms, which often kill other marine life, and help maintain the ecological balance of different species of marine blue-green algae, and thus adequate oxygen production for life on Earth. The emergence of strains of bacteria that are resistant to a broad range of antibiotics has become a problem in the treatment of bacterial infections. Only two new classes of antibiotics have been developed in the past 30 years, and novel ways of combating bacterial infections are being sought. Bacteriophages were first used to