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

Abstract

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, PVD , despite the capability and opportunity to cross-feed. We demonstrate that this strategy is beneficial in co-culture with a competing PVD -producer, P. aeruginosa PAO1. Although Pf-5 can cross-feed on PVD , production of PVD is required to maintain a competitive advantage. We attribute this to an antagonistic effect of PVD 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.

Environmental determinants of pyoverdine production, exploitation and competition in natural Pseudomonas communities

“…This is conceivable because cheating is thought to be especially harmful for producers when iron is scarce and carbon as a building block for pyoverdine is limited (Brockhurst et al ., ; Kümmerli et al ., ; Sexton and Schuster, ). Taken together, the patterns discovered here suggest that the role of pyoverdine changes with increasing iron availability: from a shareable, yet exploitable public good, to an inhibitory substance, locking iron away from competitors lacking a matching uptake receptor (Buyer and Leong, ; Butaitė et al ., ; Niehus et al ., ; Schiessl et al ., ; Sexton et al ., ).…”

Engineering Pseudomonas protegens Pf‐5 to improve its antifungal activity and nitrogen fixation

“…Pseudomonas fluorescens is well‐characterized PGPR known for its production of a broad spectrum of secondary metabolites and root colonization of wide range of hosts (Table S1; Budzikiewicz, ; Lopes et al ., , ; Khalid et al ., , ; Weber et al ., ). Pseudomonas protegens Pf‐5 (formerly Pseudomonas fluorescens Pf‐5) was isolated from the cotton rhizosphere, which typically protects plants from diseases caused by plant pathogens (Howell and Stipanovic, , ; Xu and Gross, ; Rodriguez and Pfender, ; Sexton et al ., ). At least 6% of the genome of P. protegens Pf‐5 is involved in secondary metabolite production (Paulsen et al ., 2005), including that of pyrrolnitrin (Howell and Stipanovic, , ), 2,4‐diacetylphloroglucinol (Nowak‐Thompson et al ., ), pyoluteorin (Howell and Stipanovic, ), hydrogen cyanide (Kraus and Loper, ), rhizoxin analogues (Loper et al ., ) and toxoflavin (Philmus et al ., ).…”

Receptor uptake arrays for vitamin B12, siderophores, and glycans shape bacterial communities

“…There are few observations about conditional expression of siderophore receptors (Sexton, Glover, Loper, & Schuster, 2017). I presented these speculative comments to stimulate the collection of basic data and the development of new theory.…”