A Novel Photosynthetic Strategy for Adaptation to Low-Iron Aquatic Environments

摘要

Iron (Fe) availability is a major limiting factor for primary production in aquatic environments.nCyanobacteria respond to Fe deficiency by derepressing the isiAB operon, which encodes the antenna proteinnIsiA and flavodoxin. At nanomolar Fe concentrations, a PSI-IsiA supercomplex forms, comprising a PSIntrimer encircled by two complete IsiA rings. This PSI-IsiA supercomplex is the largest photosyntheticnmembrane protein complex yet isolated. This study presents a detailed characterization of this complex usingntransmission electron microscopy and ultrafast fluorescence spectroscopy. Excitation trapping and electronntransfer are highly efficient, allowing cyanobacteria to avoid oxidative stress. Thismechanismmay be amajornfactor used by cyanobacteria to successfully adapt to modern low-Fe environments.