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
Mycorrhiza helper bacteria they found that the bacteria helped ectomycorrhizal fungi promote a symbiotic relationship with the plant by examining an increase in formation of mycorrhiza. Some bacteria improve root colonization and plant growth when associated with arbuscular mycorrhiza. The improvement of growth has been hypothesized that MHB aid the plant to defend against pathogens by improving the nutrient uptake. However, the mechanism these species use to help both of the fungi is still unknown and needs to be further investigated. Actinobacteria are gram-positive bacteria, and they are found in the soil. In this phylum, "Streptomyces" is the largest genus of bacteria, and