Photosynthetic activity and components of the electron transport chain in the aerobic bacteriochlorophyll a-containing bacterium Roseinatronobacter thiooxidans

Abstract

Bioenergetics of the aerobic bacteriochlorophyll a-containing (BCl a) bacterium (ABC bacterium) Roseinatronobacter thiooxidans is a combination of photosynthesis, oxygen respiration, and oxidation of sulfur compounds under alkaliphilic conditions. The photosynthetic activity of Rna. thiooxidans cells was established by the photoinhibition of cell respiration and reversible photobleaching discoloration of the BCl a of reaction centers (RC), connected by the chain of electron transfer with cytochrome c551 oxidation. The species under study, like many purple bacteria and some of the known ABC bacteria, possesses a light-harvesting pigment-protein (LHI) complex with the average number of 30 molecules of antenna BCl a per one photosynthetic RC. Under microaerobic growth conditions, the cells contained bc1 complex and two terminal oxidases: cbb3-cytochrome oxidase and the alternative cytochrome oxidase of the a3 type. Besides, Rna. thiooxidans was shown to have several different soluble low- and high-potential cytochromes c, probably associated with the ability of utilizing sulfur compounds as additional electron donors.