Directed evolution and characterisation of light harvesting complexes with altered spectral properties in purple non-sulfur bacteria.

Directed evolution of light-harvesting complex 2 (LH2) in Rhodobacter sphaeroides produced LH2 variants with altered B850 absorption peaks, including a blue-shift and a novel red-shift mutant.

• Why it matters: LH2 spectral tuning is important for understanding and exploring how PNSB photosystems adapt to different light environments, but systematic experimental workflows are needed.
• What they did: The study built an LH2 variant library via site-directed mutagenesis, expressed variants in an LH2-deficient Rhodobacter sphaeroides mutant, reproduced a known blue-shifted B850 mutant, and measured fluorescence lifetimes of purified spectral variants in vitro.
• The result: The observed blue- and red-shifted B850 absorption in engineered LH2s suggests directed evolution can systematically explore the light-absorption landscape of LH2 variants.

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