Glyphosate uptake pathway across the outer membrane of Pseudomonas aeruginosa

Glyphosate is a potent herbicide invented in 1974 and object of intense and sometimes contradictory toxicity studies ever since. Before crops are sown, glyphosate is sprayed onto the fields, where it gets absorbed by the soil. When glyphosate comes into contact with weeds, it inhibits a key enzyme from the shikimate pathway for the synthesis of aromatic amino acids, which is present in plants and some prokaryotes but not in animals. On the field, it can be degraded both biotically and abiotically thus interfering with the soil microorganisms like Pseudomonas aeruginosa, which metabolism can sustain on glyphosate in anaerobic conditions via a so-far unknown uptake pathway. OprO and OprP are two highly anion-selective channels involved in the high-affinity uptake of pyro- and mono-phosphate, respectively. They are present in the outer membrane of P. aeruginosa under phosphate starvation conditions. Previously, it has been demonstrated that these channels represent a favorable uptake pathway for phosphonic acid-containing antibiotics, such as fosfomycin and fosmidomycin. The object of this study is to demonstrate glyphosate permeation through OprO and OprP combining electrophysiology and molecular dynamics simulations. The results are compared with those of other substrate molecules passing through OprO and OprP to frame this study in the scenario of P. aeruginosa's outer membrane permeation properties. The present combined computational and experimental analyses provide a framework that resolves a longstanding gap in the understanding of the glyphosate uptake pathway across the outer membrane of P. aeruginosa.