title: Candida albicans ethanol stimulates Pseudomonas aeruginosa WspR-controlled biofilm formation as part of a cyclic relationship involving phenazines.
abstract: In chronic infections, pathogens are often in the presence of other microbial species. For example, Pseudomonas aeruginosa is a common and detrimental lung pathogen in individuals with cystic fibrosis (CF) and co-infections with Candida albicans are common. Here, we show that P. aeruginosa biofilm formation and phenazine production were strongly influenced by ethanol produced by the fungus C. albicans. Ethanol stimulated phenotypes that are indicative of increased levels of cyclic-di-GMP (c-di-GMP), and levels of c-di-GMP were 2-fold higher in the presence of ethanol. Through a genetic screen, we found that the diguanylate cyclase WspR was required for ethanol stimulation of c-di-GMP. Multiple lines of evidence indicate that ethanol stimulates WspR signaling through its cognate sensor WspA, and promotes WspR-dependent activation of Pel exopolysaccharide production, which contributes to biofilm maturation. We also found that ethanol stimulation of WspR promoted P. aeruginosa colonization of CF airway epithelial cells. P. aeruginosa production of phenazines occurs both in the CF lung and in culture, and phenazines enhance ethanol production by C. albicans. Using a C. albicans adh1/adh1 mutant with decreased ethanol production, we found that fungal ethanol strongly altered the spectrum of P. aeruginosa phenazines in favor of those that are most effective against fungi. Thus, a feedback cycle comprised of ethanol and phenazines drives this polymicrobial interaction, and these relationships may provide insight into why co-infection with both P. aeruginosa and C. albicans has been associated with worse outcomes in cystic fibrosis.
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America.
authors.forename: Annie I
authors.initials: AI
authors.lastname: Chen
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America.
authors.forename: Emily F
authors.initials: EF
authors.lastname: Dolben
authors.affiliation: Department of Biological Sciences, Columbia University, New York, New York, United States of America.
authors.forename: Chinweike
authors.initials: C
authors.lastname: Okegbe
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America.
authors.forename: Colleen E
authors.initials: CE
authors.lastname: Harty
authors.affiliation: Department of Microbiology, School of Medicine, University of Washington, Seattle, Washington, United States of America.
authors.forename: Yuriy
authors.initials: Y
authors.lastname: Golub
authors.affiliation: Department of Microbiology, School of Medicine, University of Washington, Seattle, Washington, United States of America.
authors.forename: Sandy
authors.initials: S
authors.lastname: Thao
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America.
authors.forename: Dae Gon
authors.initials: DG
authors.lastname: Ha
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America.
authors.forename: Sven D
authors.initials: SD
authors.lastname: Willger
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America.
authors.forename: George A
authors.initials: GA
authors.lastname: O'Toole
authors.affiliation: Department of Microbiology, School of Medicine, University of Washington, Seattle, Washington, United States of America.
authors.forename: Caroline S
authors.initials: CS
authors.lastname: Harwood
authors.affiliation: Department of Biological Sciences, Columbia University, New York, New York, United States of America.
authors.forename: Lars E P
authors.initials: LE
authors.lastname: Dietrich
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America.
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Hogan
mesh_terms: D018441:Biofilms; D002176:Candida albicans / Q000502:physiology*; D002177:Candidiasis / Q000517:prevention & control; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D000431:Ethanol / Q000494:pharmacology*; D006801:Humans; D010619:Phenazines / Q000378:metabolism*; D011550:Pseudomonas aeruginosa
chemical_list: D010619:Phenazines; D000431:Ethanol; C062025:bis(3',5')-cyclic diguanylic acid; D006152:Cyclic GMP