Eubacteria or ‘true bacteria’ are characterised by the presence of a rigid cell wall, and if motile, a flagellum. Cyanobacteria and heterotrophic bacteria are 2 categories of eubacteria. The cyanobacteria (also referred to as blue-green algae) have chlorophyll a similar to green plants and are photosynthetic autotrophs. Heterotrophic bacteria are the most abundant in nature. The majority are important decomposers.