Unlike many micro-algae and plants that only use water as an electron donor to drive photosynthesis, purple bacteria such as Rhodobacter capsulatus can switch between energy sources (light or geothermal radiation) and different electron donors depending on their surrounding environment. To do this, the bacterium must carefully control the synthesis of electron transfer proteins in response to changing conditions. However, the precise mechanisms used by R. capsulatus to sense and make use of hydrogen sulfide are unclear.
Now, Takayuki Shimizu and Shinji Masuda at the Tokyo Institute of Technology, in collaboration with David P. Giedroc and Carl E. Bauer at Indiana University and researchers across Japan and the USA, have uncovered and characterized a sulfide-responsive protein, or transcriptional repressor, called SqrR, and described the mechanism by which it responds to sulfides. The findings shed light on electron donation processes in the early evolution of photosynthesis.
Team - Protein - Gene - Responses - R
The team examined protein and gene responses in R. capsulatus. Genetic screening identified SqrR and showed that it acts as a sensor for reactive sulfide species inside cells. SqrR also regulates around 45% of the genes responsible for sulfide-dependent photosynthesis in R. capsulatus. It appears that, when sulfides in the surrounding environment increase, SqrR responds by binding to the sulfide molecules, thereby repressing photosynthetic electron transfer so that the bacterium can survive sulfide stress. In this way, SqrR helps maintain sulfide homeostasis in rapidly-changing environments.
Uncovering a major gene regulator like SqrR will allow scientists to...
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