 Abstract cydrophores are soluble or membrane-embedded molecules that bind the oxidized form of iron, Fe3. These molecules can be used by microorganisms to acquire iron, but some microbes also produce a compound called pulchrominic acid, Pa, that binds to Fe3 and forms a precipitate that reduces iron availability. This precipitate is produced when a competitor such as Pseudomonas protogens is present, and it protects the host organism from oxidative stress caused by the Fenton reaction. Additionally, the host organism can use its own cydrophore, the syllabactin, to retrieve Fe3 from the precipitate. This study shows that Pa plays multiple roles in inter-species competition, regulating both iron availability and protecting against oxidative stress. This article was authored by Vincent Sharon Lamero, Lounds Haroon, Maud Pomelo, and others.