Ion transport in microbes
Numerous ions are both essential for life and limiting in natural environments. We investigate the elaborate molecular strategies microbes use to scavenge these essential nutrients from depleted environments while excluding potentially toxic competitors.
Ions are essential nutrients for all forms of life. In particular, phosphate is indispensable, as a key component of biomolecules such as DNA, yet it is a rare nutrient in the environment, being mostly immobilized as rocks. In fact, phosphate is both an essential nutrient and an environmental pollutant, used in agriculture and causing eutrophication.
The competition for phosphate between organisms is intense, and the environmental phosphate concentration is therefore a key stimulus that regulates numerous bacterial functions, including growth and virulence.
Arsenate-rich environments are challenging because of the high similarity between the toxic arsenate and the essential phosphate anions. Our group investigates the molecular basis of microbial survival in arsenate-rich, phosphate-depleted environments.
Through the study of the Phosphate Specific Transporter (Pst) uptake system, we identified unique, highly energetic chemical bonds that shield microbes from the toxic arsenate and enable them to take up the necessary phosphate. Understanding the mechanism and the formation of these bonds is a key challenge in protein chemistry, and may provide critical insights for future developments in protein design and engineering.
We work with X-ray crystallography at ultra-high, sub-ångström resolution. At that level every atom is resolved, including hydrogen atoms, and details such as the geometry of a short hydrogen bond can be read directly from the electron density map.
Potential applications
- Cleaner water
Try it. Raise the fraction of arsenate among the ions, and phosphate still gets through. Then switch off the selectivity toggle and see what the cell would take in.
Simulation of phosphate uptake
Taken up Phosphate 0 Arsenate 0
This depicts the Pst phosphate uptake system, a key way microbes scavenge phosphate. For simplicity, the phosphate-binding protein that does the selecting is not shown: the selectivity toggle stands in for it.