Gloeobacter

Gloeobacter is a genus of cyanobacteria. It is the sister group to all other photosynthetic cyanobacteria. Gloeobacter's order, Gloeobacterales, is unique among cyanobacteria in not having thylakoids, which are characteristic for all other cyanobacteria and chloroplasts. Instead, the light-harvesting complexes (also called phycobilisomes), that consist of different proteins, sit on the inside of the plasma membrane (among the cytoplasm). Subsequently, the proton gradient in Gloeobacter is created across the plasma membrane, whereas it forms across the thylakoid membrane in cyanobacteria and chloroplasts.

The whole genome of G. violaceus (strain PCC 7421) and of G. kilaueensis have been sequenced. Many genes for photosystem I and II were found missing, likely related to the fact that photosynthesis in these bacteria does not take place in the thylakoid membrane as in other cyanobacteria, but in the plasma membrane. There is also a genome for G. morelensis.