RESUMEN
Natural photosynthesis can be divided between the chlorophyll-containing plants, algae and cyanobacteria that make up the oxygenic phototrophs and a diversity of bacteriochlorophyll-containing bacteria that make up the anoxygenic phototrophs. Photosynthetic light harvesting and reaction centre proteins from both kingdoms have been exploited for solar energy conversion, solar fuel synthesis and sensing technologies, but the energy harvesting abilities of these devices are limited by each protein's individual palette of pigments. In this work we demonstrate a range of genetically-encoded, self-assembling photosystems in which recombinant plant light harvesting complexes are covalently locked with reaction centres from a purple photosynthetic bacterium, producing macromolecular chimeras that display mechanisms of polychromatic solar energy harvesting and conversion. Our findings illustrate the power of a synthetic biology approach in which bottom-up construction of photosystems using naturally diverse but mechanistically complementary components can be achieved in a predictable fashion through the encoding of adaptable, plug-and-play covalent interfaces.
Asunto(s)
Proteínas de Arabidopsis/química , Proteínas Bacterianas/química , Bacterioclorofilas/química , Complejos de Proteína Captadores de Luz/química , Energía Solar , Biología Sintética/métodos , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/efectos de la radiación , Proteínas Bacterianas/genética , Proteínas Bacterianas/efectos de la radiación , Bacterioclorofilas/genética , Bacterioclorofilas/efectos de la radiación , Carotenoides/química , Carotenoides/efectos de la radiación , Complejos de Proteína Captadores de Luz/genética , Complejos de Proteína Captadores de Luz/efectos de la radiación , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/efectos de la radiación , Rhodobacter sphaeroides/química , Rhodobacter sphaeroides/genética , Rhodobacter sphaeroides/efectos de la radiación , Luz SolarRESUMEN
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.