Intermicrobial interaction: Aspergillus fumigatus siderophores protect against competition by Pseudomonas aeruginosa

Area of Science:

• Microbiology
• Medical Mycology
• Infectious Diseases

Background:

• Pseudomonas aeruginosa and Aspergillus fumigatus frequently co-infect immunocompromised patients, especially those with cystic fibrosis.
• Both pathogens require iron and compete for it in their shared airway environment.
• P. aeruginosa siderophore pyoverdine previously demonstrated efficacy against A. fumigatus biofilms via iron chelation.

Purpose of the Study:

• To investigate the role of Aspergillus fumigatus siderophores in mediating inter-species competition with Pseudomonas aeruginosa.
• To determine if A. fumigatus siderophores confer resistance against P. aeruginosa's anti-fungal effects.

Main Methods:

• Comparative analysis of P. aeruginosa's anti-fungal activity against A. fumigatus biofilms with and without A. fumigatus siderophores.
• Assessment of A. fumigatus sidA gene deletion mutant (AfΔsidA) biofilms' sensitivity to P. aeruginosa, pyoverdine, deferiprone (DFP), and amphotericin B.
• Evaluation of siderophore supplementation effects on AfΔsidA biofilm resistance.
• Testing the impact of A. fumigatus siderophore inhibitor celastrol on biofilm sensitivity to DFP.

Main Results:

• A. fumigatus siderophores significantly protected fungal biofilms from P. aeruginosa's inhibitory effects.
• A. fumigatus biofilms lacking siderophore production (AfΔsidA) were more susceptible to P. aeruginosa, pyoverdine, DFP, and amphotericin B.
• Supplementation with A. fumigatus siderophores restored resistance in AfΔsidA biofilms.
• Inhibiting A. fumigatus siderophore production increased biofilm susceptibility to DFP.

Conclusions:

• A. fumigatus hydroxamate siderophores are critical for iron competition against P. aeruginosa.
• These fungal siderophores play a key role in defending A. fumigatus biofilms against bacterial interference and antifungal agents.