A seventh bacterial chlorophyll driving a large light-harvesting antenna

The discovery of new chlorophyllous pigments would provide greater understanding of the mechanisms and evolution of photosynthesis. Bacteriochlorophyll f has never been observed in nature, although this name was proposed ~40 years ago based on structurally related compounds. We constructed a bacteriochlorophyll f –accumulating mutant of the green sulfur bacterium Chlorobaculum limnaeum , which originally produced bacteriochlorophyll e , by knocking out the bchU gene encoding C-20 methyltransferase based on natural transformation. This novel pigment self-aggregates in an in vivo light-harvesting antenna, the chlorosome and exhibits a Q y peak of 705 nm, more blue-shifted than any other chlorosome reported so far; the peak overlaps the maximum (~700 nm) of the solar photon flux spectrum. Bacteriochlorophyll f chlorosomes can transfer light energy from core aggregated pigments to another bacteriochlorophyll in the chlorosomal envelope across an energy gap of ~100 nm and is thus a promising material for development of new bioenergy applications.