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

Area of Science:

• Microbiology
• Biochemistry
• Ecology

Background:

• Microorganisms compete for iron using siderophores, which bind iron and require specific receptors for import.
• Cross-feeding, utilizing siderophores from other species, is common but poorly understood in terms of regulation.
• Pseudomonas protegens Pf-5 utilizes numerous heterologous siderophores, making it an ideal model for studying this behavior.

Purpose of the Study:

• Investigate the regulation of siderophore receptor expression in Pseudomonas protegens Pf-5.
• Determine the competitive strategy of Pf-5 when co-cultured with other siderophore-producing bacteria.
• Elucidate the role of self-produced siderophores in inter-species competition.

Main Methods:

• Characterized the expression of six pyoverdine-type (PVD) siderophore receptors in Pf-5.
• Assessed Pf-5's ability to cross-feed on heterologous siderophores.
• Conducted co-culture experiments with P. aeruginosa PAO1 to evaluate competitive interactions.

Main Results:

• Siderophore receptor expression in Pf-5 is tightly regulated by the availability of cognate siderophores.
• Pf-5 continues to produce its own siderophore, PVD_Pf-5, even when cross-feeding is possible.
• Production of PVD_Pf-5 provides a competitive advantage against P. aeruginosa PAO1 by limiting the competitor's iron access.

Conclusions:

• Pseudomonas protegens Pf-5 prioritizes self-siderophore production for competitive exclusion over opportunistic cross-feeding.
• The strategy of actively inhibiting competitors' iron uptake is more beneficial than relying on others' siderophores.
• This study reveals the ecological advantages of competitive iron acquisition strategies in microbial communities.