SEMINAR: How bacterial photosynthesis works

Abstract

Photosynthesis, the ultimate source of all food and most energy resources on Earth, starts with the absorption of solar energy. However, sunlight is a diffuse energy source so an extensive light-harvesting antenna, consisting of many hundreds of pigment molecules, is needed to collect the light. Absorbed energy is channelled towards specialised chlorophyll-protein complexes called reaction centres, initiating a series of electron transfer reactions that capture some of the solar energy prior to storage in a chemical form that powers the metabolism of the cell. In this lecture I will explain how the relatively simple photosynthetic bacteria provide useful systems for investigating the molecular details of photosynthesis. We have used X-ray crystallography to discover the 3D structure of a light harvesting-reaction centre complex, and atomic force microscopy shows us how individual complexes form extensive membrane networks for light harvesting and energy trapping. Maps of these membrane networks have allowed computation of atomic-level models of whole membrane assemblies that predict energy transfer and trapping behaviour and identify desirable design motifs for new photosynthetic systems. The lecture will conclude by showing how synthetic biology approaches might enhance solar energy collection by photosynthetic membranes.