Fighting for limiting resources: iron uptake strategies in cyanobacteria
Cyanobacteria are gram negative prokaryotes that are major contributors to global primary productivity. These aquatic microbes require as much as 10 times more iron than non-photosynthetic prokaryotes and are exceptional even among other photosynthetic organisms in their iron requirements. In many marine and freshwater environments, iron bioavailability limits phototrophic growth implicating iron as an important factor in global primary productivity. Yet little is known about the mechanisms by which cyanobacteria acquire iron. At the Keren Lab, we are trying to elucidate these mechanisms. The findings of this research are expected to provide mechanistic knowledge of iron bioavailability and the strategies by which these fascinating microorganisms acquire iron from the environment.
My research focuses on the mechanisms of iron transport in the model, planktonic cyanobacterium, Synechocystis sp PCC 6803. We identified a previously uncharacterized mode of transport in cyanobacteria called reductive iron uptake. Reductive iron uptake involves the reduction of Fe(III) species to Fe(II) prior to transport into the cell. Given its broad range of substrates, reductive iron uptake may be applied to a variety of Fe sources. This generalist type strategy would confer an obvious advantage to organisms living in a dilute and heterogeneous aquatic environment in which iron is bound by many different organic chelators. This project includes establishing the kinetics of transport as well as the molecular components of this pathway by applying tools from the fields of molecular biology, biophysics, biochemistry and geochemistry.