Adaptation of Rhodopseudomonas acidophila strain 7050 to growth at different light intensities: what are the benefits to changing the type of LH2?

A T Gardiner,D M Niedzwiedzki,R J Cogdell

doi:10.1039/c7fd00191f

A T Gardiner, D M Niedzwiedzki + Show 1 more

Open Access

https://doi.org/10.1039/c7fd00191f

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Abstract

Typical purple bacterial photosynthetic units consist of light harvesting one/reaction centre 'core' complexes surrounded by light harvesting two complexes. Factors such as the number and size of photosynthetic units per cell, as well as the type of light harvesting two complex that is produced, are controlled by environmental factors. In this paper, the change in the type of LH2 present in the Rhodopsuedomonas acidophila strain 7050 is described when cells are grown at a range of different light intensities. This species contains multiple pucBA genes that encode the apoproteins that form light-harvesting complex two, and a more complex mixture of spectroscopic forms of this complex has been found than was previously thought to be the case. Femto-second time resolved absorption has been used to investigate how the energy transfer properties in the membranes of high-light and low-light adapted cells change as the composition of the LH2 complexes varies.

Highlights

The primary reactions of purple bacterial photosynthesis involve light harvesting (LH) complexes and reaction centres (RC) that are located in intracytoplasmic membranes (ICM).[1]
This is important as the purple bacterial light harvesting system is subject to regulation by the wavelength of the incident radiation as well as its intensity.[28,29]
It is dominated by peaks at 800 and $850 nm that embody the typical high light (HL) form of LH2

Summary

Introduction

The primary reactions of purple bacterial photosynthesis involve light harvesting (LH) complexes and reaction centres (RC) that are located in intracytoplasmic membranes (ICM).[1] Light energy absorbed by the light harvesting system is transferred to the RCs where it is trapped by a series of transmembrane electron transfer reactions. The cell’s capacity for LH is exible and can be adjusted in response to environmental factors, such as the incident light intensity.[2,3] Under low light (LL) conditions there is an extensive system of ICM in the cell, whereas under high light (HL) conditions the amount of ICM is a lot less. The LH1 complexes surround the RC to form the so called ‘core’ complex, with the LH2 complexes arranged more peripherally around the core complexes.[4,5,6] The incident light

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