On the photosynthetic properties of marine bacterium COL2P belonging to Roseobacter clade.
Aerobic anoxygenic phototrophs (AAPs) are prokaryotic microorganisms capable of harvesting light using bacteriochlorophyll-based reaction centres. Marine AAP communities are generally dominated by species belonging to the Roseobacter clade. For this reason, we used marine Roseobacter-related strain COL2P as a model organism to characterize its photosynthetic apparatus, level of pigmentation and expression of photosynthetic complexes. This strain contained functional photosynthetic reaction centres with bacteriochlorophyll a and spheroidenone as the main light-harvesting pigments, but the expression of the photosynthetic apparatus was significantly reduced when compared to truly photoautotrophic species. Moreover, the absence of peripheral light-harvesting complexes largely reduced its light-harvesting capacity. The size of the photosynthetic unit was limited to 35.4 +/- 1.0 BChl a molecules supplemented by the same number of spheroidenone molecules. The contribution of oxidative phosphorylation and photophosphorylation was analysed by respiration and fluorometric measurements. Our results indicate that even with a such reduced photosynthetic apparatus, photophosphorylation provides up to three times higher electron fluxes than aerobic respiration. These results suggest that light-derived energy can provide a substantial fraction of COL2P metabolic needs.
Koblízek
Michal
M
Institute of Microbiology CAS, Opatovický mlýn, Trebon, Czech Republic. koblizek@alga.cz
Mlcousková
Jarmila
J
Kolber
Zbigniew
Z
Kopecký
Jirí
J
D000332:Aerobiosis / Q000235:genetics; D000595:Amino Acid Sequence; D000693:Anaerobiosis / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D025541:Bacteriochlorophyll A / Q000235:genetics; D001429:Bacteriochlorophylls / Q000235:genetics; D002338:Carotenoids / Q000378:metabolism; D003227:Conjugation, Genetic; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008027:Light; D010101:Oxygen Consumption / Q000235:genetics; D010785:Photophosphorylation; D010788:Photosynthesis / Q000235:genetics; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics; D010802:Phylogeny; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D041904:Roseobacter / Q000235:genetics / Q000378:metabolism*; D012623:Seawater
D001426:Bacterial Proteins; D025541:Bacteriochlorophyll A; D001429:Bacteriochlorophylls; D045322:Photosynthetic Reaction Center Complex Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; C104880:spheroidenone; D002338:Carotenoids