Phosphorus is absolutely necessary for all life on the planet. It is present in DNA, cell membranes and the energy carrier ATP. However, it’s not an unlimited resource. The main bioavailable form of phosphorus is phosphate. When there is too much phosphate in the environment, microbial growth is stimulated. When phosphate amounts are limited, some bacteria manage to use phosphite or hypophosphite as a source of phosphorus. But these molecules are present in limited amounts, leading researchers to ask, “How do bacteria scavenge these alternative sources of phosphorus?”
Scientists from the University of Sheffield used a combination of MST and structural studies to understand how bacterial ABC transporters bind phosphite and hypophosphite, which microorganisms use to capture reduced phosphorus from the environment. Mutation of the ligand-binding pocket led to large changes in affinity, which were readily and reproducibly measured using MST. Nine different periplasmic binding proteins part of the bacterial ABC transporters were labeled with a His-tag dye and their affinity to multiple phosphorus compounds was measured. From their experiments, these scientists discovered how bacteria could use phosphite as an alternative source of phosphorus. The findings show that phosphite could be a backup energy source in biotechnological, industrial and agricultural applications.