Transporter characterisation reveals aminoethylphosphonate mineralisation as a key step in the marine phosphorus redox cycle

Abstract The planktonic synthesis of reduced organophosphorus molecules, such as alkylphosphonates and aminophosphonates, represents one half a vast global oceanic phosphorus redox cycle. Whilst tend to accumulate in recalcitrant dissolved organic matter, aminophosphonates do not. Here, we identify three bacterial 2-aminoethylphosphonate (2AEP) transporters, named AepXVW, AepP AepSTU, whose is independent phosphate concentrations (phosphate-insensitive). AepXVW found diverse marine heterotrophs ubiquitously distributed mesopelagic epipelagic waters. Unlike the archetypal phosphonate binding protein, PhnD, AepX has high affinity specificity for 2AEP ( Stappia stellulata K d 23 ± 4 nM; methylphosphonate 3.4 0.3 mM). In ocean, aepX heavily transcribed (~100-fold> phnD ) independently nitrogen concentrations. Collectively, our data identifies mechanism responsible major oxidation process cycle suggests may be an important source regenerated ammonium, which are required primary production.