Abstract
Photosynthetic organisms rely on antenna systems to harvest and deliver energy from light to reaction centers. In fluctuating photic environments, regulation of light harvesting is critical for a photosynthetic organism's survival. Here, we describe the use of a suite of phycobilisome mutants to probe the consequences of antenna truncation in the cyanobacterium Synechocystis sp. PCC 6803. Studies using transmission electron microscopy (TEM), hyperspectral confocal fluorescence microscopy (HCFM), small-angle neutron scattering (SANS), and an optimized photobioreactor system have unraveled the adaptive strategies that cells employ to compensate for antenna reduction. As the phycobilisome antenna size decreased, changes in thylakoid morphology were more severe and physical segregation of the two photosystems increased. Repeating distances between thylakoid membranes measured by SANS were correlated with TEM data, and corresponded to the degree of phycobilisome truncation. Thylakoid membranes were found to have a high degree of structural flexibility, and changes in the membrane system upon illumination were rapid and reversible. Phycobilisome truncation in Synechocystis 6803 reduced the growth rate and lowered biomass accumulation. Together, these results lend a dynamic perspective to the intracellular membrane organization in cyanobacteria cells and suggest an adaptive mechanism that allows cells to adjust to altered light absorption capabilities, while highlighting the cell-wide implications of antenna truncation.
Original language | English |
---|---|
Pages (from-to) | 17-24 |
Number of pages | 8 |
Journal | Photosynthesis Research |
Volume | 118 |
Issue number | 1-2 |
DOIs | |
State | Published - Nov 2013 |
Funding
Acknowledgments The authors thank Ghada Ajlani for the kind gift of the phycobilisome mutant strains described in this study, Michael Sinclair for the maintenance and use of the hyperspectral confocal fluorescence microscope, and Howland Jones for the development of the multivariate analysis software. The authors also thank Howard Berg of the Donald Danforth Plant Science Center’s Integrated Microscopy Facility for TEM assistance. This material is based upon work supported as part of the Photosynthetic Antenna Research Center (PARC), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC 0001035. The Bio-SANS instrument is a resource of the Center for Structural Molecular Biology at Oak Ridge National Laboratory that is supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research Project ERKP291. Bio-SANS is located at the Oak Ridge National Laboratory’s High Flux Isotope Reactor. The neutron source is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.
Keywords
- Cyanobacteria
- Hyperspectral imaging
- Neutron scattering
- Photobioreactor
- Photosynthesis
- Thylakoid