Clades of Photosynthetic Bacteria Belonging to the GenusRhodopseudomonasShow Marked Diversity in Light-Harvesting Antenna Complex Gene Composition and Expression.
Many photosynthetic bacteria have peripheral light-harvesting (LH) antenna complexes that increase the efficiency of light energy capture. The purple nonsulfur photosynthetic bacteriumRhodopseudomonas palustrisproduces different types of LH complexes under high light intensities (LH2 complex) and low light intensities (LH3 and LH4 complexes). There are multiplepucBAoperons that encode the α and β peptides that make up these complexes. However, low-resolution structures, amino acid similarities between the complexes, and a lack of transcription analysis have made it difficult to determine the contributions of differentpucBAoperons to the composition and function of different LH complexes. It was also unclear how much diversity of LH complexes exists inR. palustrisand affiliated strains. To address this, we undertook an integrative genomics approach using 20 sequenced strains. Gene content analysis revealed that even closely related strains have differences in theirpucBAgene content. Transcriptome analyses of the strains grown under high light and low light revealed that the patterns of expression of thepucBAoperons varied among strains grown under the same conditions. We also found that one set of LH2 complex proteins compensated for the lack of an LH4 complex under low light intensities but not under extremely low light intensities, indicating that there is functional redundancy between some of the LH complexes under certain light intensities. The variation observed in LH gene composition and expression inRhodopseudomonasstrains likely reflects how they have evolved to adapt to light conditions in specific soil and water microenvironments.IMPORTANCERhodopseudomonas palustrisis a phototrophic purple nonsulfur bacterium that adapts its photosystem to allow growth at a range of light intensities. It does this by adjusting the amount and composition of peripheral light-harvesting (LH) antenna complexes that it synthesizes.Rhodopseudomonasstrains are notable for containing numerous sets of light-harvesting genes. We determined the diversity of LH complexes and their transcript levels during growth under high and low light intensities in 20 sequenced genomes of strains related to the speciesRhodopseudomonas palustris. The data obtained are a resource for investigators with interests as wide-ranging as the biophysics of photosynthesis, the ecology of phototrophic bacteria, and the use of photosynthetic bacteria for biotechnology applications.
Department of Microbiology, University of Washington, Seattle, Washington, USA.
Kathryn R
KR
Fixen
Department of Microbiology, University of Washington, Seattle, Washington, USA.
Yasuhiro
Y
Oda
Department of Microbiology, University of Washington, Seattle, Washington, USA.
Caroline S
0000-0003-4450-5177
CS
Harwood
biotechnology; phototrophs; transcriptomics