Gloeobacter is a genus of cyanobacteria. It is a sister group to all other cyanobacteria. Gloeobacter is unique among cyanobacteria in not having thylakoids. The proton gradient of Gloeobacter forms along the plasma membrane where the phycobilisomes are attached to the cytoplasmic side.
The whole genome of Gloeobacter violaceus (strain PCC 7421) has been sequenced. Many genes for Photosystem I and II were found missing, likely related to the fact that photosynthesis in the bacterium does not take place in the thylakoid membrane like in other cyanobacteria, but in the plasma membrane