Summary
Many microorganisms live in habitats providing soluble metal concentrations below the intracellular concentrations required for optimal cellular growth. To counteract such nutrient limitations, microorganisms have evolved small chelating compounds (ionophores) to sequester metal ions from the environment. Ionophores typically form metal complexes that serve to shuttle the metal ion across a lipid barrier and enable intracellular access for the metal.
The complexing agents are either taken up in the loaded state via specific channels of the cell, or the metal ion is transported alone in the cell. As a result, microorganisms are supplied with trace elements such as manganese, iron, cobalt, nickel, copper or zinc, which occur in nature only in very low concentrations. These metals, as components of cofactors or enzymes, are catalytically active and absolutely vital. Thus complexing agents play an important role in the ecology of microorganisms. The survival of microorganisms in the soil depends on their ability to absorb metal ions. Interestingly, many bacteria cannot produce complexing agents themselves, but can use them from other bacteria or fungi, thereby surviving metal iron deficiency.
[S,S]-Ethylenediamine disuccinate (EDDS) is synthesized by the soil bacterium actinomycete Amycolatopsis japonicum only under zinc-limited conditions in order to supply the cell with zinc under zinc deficiency conditions and thus to ensure its survival. By analogy with the siderophores synthesized under iron deficiency conditions, EDDS is referred to as the zincophore.
The EDDS biosynthesis genes have been identified and the zinc regulation have been elucidated. A zinc-deregulated mutant A. japonicum_Dzur could be generated, which produces EDDS even in the presence of high zinc concentrations (Spohn et al., 2016).
In the framework of this project, the following questions will be answered:
- What zinc uptake strategies has A. japonicum developed to survive zinc deficiency?
- Are other microorganisms able to take up [S,S]-EDDS-metal-complexes under metal-deficient conditions?
- How does the composition of microorganisms change in the presence of various A. japonicum strains producing different amounts of [S,S]-EDDS?
