The fitness benefit of pyoverdine cross‐feeding by Pseudomonas protegens Pf‐5

Abstract

Under iron‐limiting conditions, fluorescent pseudomonads acquire iron from the environment by secreting strain‐specific, iron‐chelating siderophores termed pyoverdines (PVD). The rhizosphere bacterium Pseudomonas protegens Pf‐5 produces its own PVD but also can cross‐feed on PVDs produced by other species. Previous work has found that Pf‐5 continues to produce its own PVD when allowed to cross‐feed, raising questions about the benefit of heterologous PVD utilisation. Here, we investigate this question using a defined, unidirectional P. protegens Pf‐5/Pseudomonas aeruginosa PAO1 cross‐feeding model. Quantifying the production of PVD in the presence of heterologous PVD produced by PAO1, we show that cross‐feeding Pf‐5 strains reduce the production of their own PVD, while non‐cross‐feeding Pf‐5 strains increase the production of PVD. Measuring the fitness of cross‐feeding and non‐cross‐feeding Pf‐5 strains in triple coculture with PAO1, we find that cross‐feeding provides a fitness benefit to Pf‐5 when the availability of heterologous PVD is high. We conclude that cross‐feeding can reduce the costs of self‐PVD production and may thus aid in the colonisation of iron‐limited environments that contain compatible siderophores produced by other resident microbes. Taken together, these results expand our understanding of the mechanisms of interspecific competition for iron in microbial communities.