Dynamic proteome response of a marine Vibrio to a gradient of iron and ferrioxamine bioavailability

Abstract

Competition for limited iron resources is a key driver of microbial community structure in many regions of the surface ocean. The bacterial siderophores ferrioxamine and amphibactin have been identified in marine surface waters, suggesting that they may represent an important bacterial strategy for obtaining iron from a scarcely populated pool. Using proteomics, siderophore isolation, and iron uptake experiments, we observed a dynamic proteome response to iron and ferrioxamine treatments by the amphibactin-producing marine bacterium, Vibrio cyclitrophicus str. 1F-53 (V. cyclitrophicus). Proteomic analyses identified upregulation of the amphibactin NRPS system and a putative amphibactin siderophore transporter in response to low iron concentrations. However, when desferrioxamine was present, amphibactin production decreased and an uncharacterized putative ferrioxamine receptor increased in abundance. This suggests that in low Fe conditions, V. cyclitrophicus senses and takes up exogenous ferrioxamine in lieu of producing its own siderophores. Such cheating phenotypes, which appear widespread among marine amphibactin producers, highlight the strategies that contribute to the fitness of marine bacteria in the face of iron stress. These results provide mechanistic information behind the siderophore producer and cheater phenotypes that likely contribute to the ecological success of these microbes across iron-limited marine ecosystems.