On the Edge of the Rainbow: Red-Shifted Chlorophylls and Far-Red Light Photoadaptation in Cyanobacteria

The phenomenon of photosynthetic adaptation of cyanobacteria to far-red light (FRL; 700-750 nm) is closely related to such basic themes as: phototrophy, microbial ecology, and diversity of bacteria. In applied terms, this bioenergetic strategy is essential for biotechnology, with a perspective to possess additional photosynthetic energy. The majority of cyanobacteria is known to use 400-700 nm light, excited state being channeled from light-harvesting complex to reaction centers of two photosystems containing chlorophyll (Chl) a showing red maxima at similar to 700 nm. After the isolation of first strains producing Chls d and fit became clear that cyanobacteria can also use FRL. Large amount of data has been obtained on cyanobacteria which constitutively produce Chl d as well as on those strains which produce Chlf or Chlf/Chl d during FRL photoacclimation (FaRLiP). Inclusion of these pigments in photosynthetic apparatus, particularly using FaRLiP mechanisms, augments the adaptive potential of cyanobacteria and expands their distribution range. The review provides evidence on such aspects as: photosynthetic apparatus containing Chl d or Chld/Chlf; the FaRLiP gene cluster; phylogeny of cyanobacteria which constitutively or inducibly produce red-shifted chlorophylls; the use of chlorophylls in chemotaxonomy of cyanobacteria, and application of this character in nomenclature.