From Antagonism to Synergism: Roles of Different Phenazines in Bacterial-Fungal Interactions between Pseudomonas aeruginosa and Aspergillus fumigatus

H. Zheng, M. Liew, X. Lu, Y. Wang


Secreted redox-active molecules, such as phenazines produced by Pseudomonas bacteria, are increasingly recognized to mediate many types of bacterial-fungal interactions in nature and the clinical environments. However, little is known about the molecular mechanisms underlying these interactions and their potential impacts on human and ecosystem health. By combining physiological, genetic and metabolic profiling strategies, here we aim to understand the roles of redox-active phenazines in co-culture biofilm interactions between the ubiquitous opportunistic bacterial and fungal pathogens, Pseudomonas aeruginosa and Aspergillus fumigatus, respectively. The phenazine production patterns in our co-culture biofilm experiments performed on solid medium indicate that phenazines may affect P. aeruginosa - A. fumigatus interactions in multiple ways. We have found that the fungusA. fumigatus inhibits the bacterium P. aeruginosa colony development, which can be differentially rescued upon phenazine production. With some phenazines, such as phenazine-1-carboxylic acid (PCA) and phenazine-1-carboxamide (PCN), the rescue decreases asexual spore (conidia) formation in A. fumigatus, complying with antifungal activity. Conversely, the phenazine pyocyanin (PYO) enhances A. fumigatus conidia formation as well as elicits rescue on P. aeruginosa colony development. In addition, A. fumigatus can modify the precursor phenazine PCA to make at least three other phenazines. Our findings imply that phenazines have profound and diverse effects on each organism’s behavior and physiology, thus contribute to shaping the ecological structure under such a competitive and mixed-species encounter.

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American Society for Microbiology General Meeting
    • ASM 112th (2012)