5 years ago

Pseudomonas protegens Pf-5 favours self-produced siderophore over free-loading in interspecies competition for iron

D. Joseph Sexton, Martin Schuster, Joyce E. Loper, Rochelle C. Glover
Many microorganisms compete for extracellular iron using strain-specific chelators known as siderophores. The ferric-siderophore complex limits local access to iron because import requires a suitable cognate receptor. Interestingly, many species carry receptors that enable ‘cross-feeding’ on heterologous siderophores made by neighboring organisms, although little is known about how this ubiquitous behaviour is regulated. Here, we investigated the soil bacterium Pseudomonas protegens Pf-5, a strain remarkable for its ability to use dozens of heterologous siderophores. We characterized the expression of six pyoverdine-type (PVD) siderophore receptors in response to their cognate PVD. In general, we found expression is tightly regulated to reflect availability of their cognate PVD. In contrast, Pf-5 continues to secrete its own primary siderophore, PVDPf-5, despite the capability and opportunity to cross-feed. We demonstrate that this strategy is beneficial in co-culture with a competing PVDPAO1-producer, P. aeruginosa PAO1. Although Pf-5 can cross-feed on PVDPAO1, production of PVDPf-5 is required to maintain a competitive advantage. We attribute this to an antagonistic effect of PVDPf-5 on the growth of PAO1, presumably through limiting access to iron. Our results demonstrate the benefits of excluding competitors out-weigh the incentives associated with a free-loader lifestyle for Pf-5.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/1462-2920.13836

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