Bioenergetics in a Primordial Cyanobacterium Gloeobacter violaceus PCC 7421

Bioenergetics of a primordial cyanobacterium Gloeobacter violaceus PCC 7421 were discussed based on genome information and experimental results. Absence of thylakoid membranes in this species induced inevitable coupling of the two electron transfer systems, i.e. photosynthesis and respiration, on cytoplasmic membranes by sharing common components. There were multiple pathways for a respiratory electron transfer system, and they affected the redox state of quinone molecules in the pool through the redox equilibrium among components. Even though experimental analysis on this species was not abundant, a principal point of the energetics is now becoming clear. In addition, a whole genome analysis and comparative genomics brought about many important informations on the components for photosynthesis, respiration, metabolism, and regulation. In many cases, this species lacks genes related to bioenergetics, however malfunction of the system was not necessarily observed, indicating presence of an alternative way to establish reaction systems found in other cyanobacterial species. By a combination of the two kinds of information, we discussed the bioenergetics in the unique species, G. violaceus.