Pyoverdine production by Pseudomonas aeruginosa exposed to metals or an oxidative stress agent

Siderophores are low molecular mass compounds used by many microorganisms to scavenge dissolved iron, which is typically rare in environments. Pseudomonas aeruginosa (PAO1) was exposed to metals and methyl viologen in low-iron medium in order to monitor the abundance of a specific siderophore (pyoverdine) and monitor growth over time. In this study it was discovered that cadmium can stimulate pyoverdine abundance. Cadmium may interact with and sequester the Fur regulatory protein, which represses siderophore synthesis under conditions of iron sufficiency. Mercury did not stimulate pyoverdine production at concentrations that strongly inhibited bacterial growth, suggesting that pyoverdine production is not governed as part of a general stress response: Methyl viologen is an oxygen radical generator, and it was discovered that exposure to it decreased pyoverdine production. Decreased pyoverdine production may be a mechanism for reducing the iron potentiation of oxygen toxicity. It is hypothesized that factors stimulating production of siderophores may increase the susceptibility of microorganisms to oxidative damage. In general, our research suggests new opportunities for predicting ecotoxicological outcomes based on understanding of molecular mechanisms and the effect of xenobiotics or stress factors on fundamentally important microbial processes.