Cyanobacteria, green sulfur bacteria, and purple bacteria create energy by a process called photophosphorylation.
Others are free-living, such as Rhodopseudomonas, a purple bacterium found in marine water and soils.
Their ancestors appear to be purple nonsulfur bacteria, and they have arisen independently several times during evolution.
Thus, it is of considerable interest that, in essence, the same structure is found in purple bacteria.
A year later Engelmann discovered that purple bacteria utilise ultraviolet light in the same way.
The Rhodospirillaceae include mainly purple non-sulfur bacteria, which produce energy through photosynthesis.
Among others, they include Rhodomicrobium, a genus of purple bacteria.
Studies revealed that the closest relatives were the purple nonsulfur phototrophic bacteria.
These are called purple bacteria, referring to their mostly reddish pigmentation.
Only subsequently, this occurred: for example, the "purple bacteria and relatives" were renamed Proteobacteria.