The chlorosome: a prototype for efficient light harvesting in photosynthesis

Abstract

Three phyla of bacteria include phototrophs that contain unique antenna systems, chlorosomes, as the principal light-harvesting apparatus. Chlorosomes are the largest known supramolecular antenna systems and contain hundreds of thousands of BChl c/d/e molecules enclosed by a single membrane leaflet and a baseplate. The BChl pigments are organized via self-assembly and do not require proteins to provide a scaffold for efficient light harvesting. Their excitation energy flows via a small protein, CsmA embedded in the baseplate to the photosynthetic reaction centres. Chlorosomes allow for photosynthesis at very low light intensities by ultra-rapid transfer of excitations to reaction centres and enable organisms with chlorosomes to live at extraordinarily low light intensities under which no other phototrophic organisms can grow. This article reviews several aspects of chlorosomes: the supramolecular and molecular organizations and the light-harvesting and spectroscopic properties. In addition, it provides some novel information about the organization of the baseplate.

Theoretical characterization of excitation energy transfer in chlorosome light-harvesting antennae from green sulfur bacteria

“…The uncertainty in the structural characterization of chlorosomes stems from the large disorder in aggregates composing the chlorosome. The chlorosome is considered to be the largest and most efficient light-harvesting antenna systems found in nature [6][7][8][9][10][11]. This observation motivates a strong interest in the design of artificial light-harvesting systems that uses aggregates of pigment or dye molecules [12][13][14][15][16].…”

Fast Exciton Dynamics and Coherent Oscillations Revealed by Coherent 2D Spectroscopy in Chlorosomes

“…Fast photophysical processes following an excitation of chlorosome Q y band were studied by several groups (for review see [1,4]). It was reported that initial fast exciton relaxation occurring in less than 1 ps is followed by the long-range energy equilibration inside the chlorosome.…”

Chlorophylls, Symmetry, Chirality, and Photosynthesis

“…Typically J-aggregation occurs due to coordination between the Mg and 3′-OH, H-bonding between the 3′-OH and the 13-C=O and π-π interactions between the macrocycles, in addition to electrostatic interactions (e.g., the polarized keto group and the Mg atom) and the partitioning of the long chain farnesyl groups into the hydrophobic parts of the construct. Through various spectroscopic and microscopic techniques, it has been shown that these aggregates form both rod-like elements and lamellar sheets within the chlorosome [263][264][265][266].…”