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Flexible survival strategies of Pseudomonas aeruginosa in biofilms result in increased fitness compared with Candida albicans.

ABSTRACT: The majority of microorganisms persist in nature as surface-attached communities often surrounded by an extracellular matrix, called biofilms. Most natural biofilms are not formed by a single species but by multiple species. Microorganisms not only cooperate as in some multispecies biofilms but also compete for available nutrients. The Gram-negative bacterium Pseudomonas aeruginosa and the polymorphic fungus Candida albicans are two opportunistic pathogens that are often found coexisting in a human host. Several models of mixed biofilms have been reported for these organisms showing antagonistic behavior. To investigate the interaction of P. aeruginosa and C. albicans in more detail, we analyzed the secretome of single and mixed biofilms of both organisms using MALDI-TOF MS/MS at several time points. Overall 247 individual proteins were identified, 170 originated from P. aeruginosa and 77 from C. albicans. Only 39 of the 131 in mixed biofilms identified proteins were assigned to the fungus whereby the remaining 92 proteins belonged to P. aeruginosa. In single-species biofilms, both organisms showed a higher diversity of proteins with 73 being assigned to C. albicans and 154 to P. aeruginosa. Most interestingly, P. aeruginosa in the presence of C. albicans secreted 16 proteins in significantly higher amounts or exclusively among other virulence factors such as exotoxin A and iron acquisition systems. In addition, the high affinity iron-binding siderophore pyoverdine was identified in mixed biofilms but not in bacterial biofilms, indicating that P. aeruginosa increases its capability to sequester iron in competition with C. albicans. In contrast, C. albicans metabolism was significantly reduced, including a reduction in detectable iron acquisition proteins. The results obtained in this study show that microorganisms not only compete with the host for essential nutrients but also strongly with the present microflora in order to gain a competitive advantage.

SUBMITTER: Purschke FG

PROVIDER: S-EPMC3518115 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

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Flexible survival strategies of Pseudomonas aeruginosa in biofilms result in increased fitness compared with Candida albicans.

Purschke Frauke Gina FG Hiller Ekkehard E Trick Iris I Rupp Steffen S

Molecular & cellular proteomics : MCP 20120831 12

The majority of microorganisms persist in nature as surface-attached communities often surrounded by an extracellular matrix, called biofilms. Most natural biofilms are not formed by a single species but by multiple species. Microorganisms not only cooperate as in some multispecies biofilms but also compete for available nutrients. The Gram-negative bacterium Pseudomonas aeruginosa and the polymorphic fungus Candida albicans are two opportunistic pathogens that are often found coexisting in a hu ...[more]

PMID: 22942357

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Project description:The polymicrobial nature of ventilator-associated pneumonia (VAP) is now evident, with mixed bacterial-fungal biofilms colonizing the VAP endotracheal tube (ETT) surface. The microbial interplay within this infection may contribute for enhanced pathogenesis and exert impact towards antimicrobial therapy. Consequently, the high mortality/morbidity rates associated to VAP and the worldwide increase in antibiotic resistance has promoted the search for novel therapeutic strategies to fight VAP polymicrobial infections. Under this scope, this work aimed to assess the activity of mono- vs combinational antimicrobial therapy using one antibiotic (Polymyxin B; PolyB) and one antifungal (Amphotericin B; AmB) agent against polymicrobial biofilms of Pseudomonas aeruginosa and Candida albicans. The action of isolated antimicrobials was firstly evaluated in single- and polymicrobial cultures, with AmB being more effective against C. albicans and PolyB against P. aeruginosa. Mixed planktonic cultures required equal or higher antimicrobial concentrations. In biofilms, only PolyB at relatively high concentrations could reduce P. aeruginosa in both monospecies and polymicrobial populations, with C. albicans displaying only punctual disturbances. PolyB and AmB exhibited a synergistic effect against P. aeruginosa and C. albicans mixed planktonic cultures, but only high doses (256 mg L-1) of PolyB were able to eradicate polymicrobial biofilms, with P. aeruginosa showing loss of cultivability (but not viability) at 2 h post-treatment, whilst C. albicans only started to be inhibited after 14 h. In conclusion, combination therapy involving an antibiotic and an antifungal agent holds an attractive therapeutic option to treat severe bacterial-fungal polymicrobial infections. Nevertheless, optimization of antimicrobial doses and further clinical pharmacokinetics/pharmacodynamics and toxicodynamics studies underpinning the optimal use of these drugs are urgently required to improve therapy effectiveness and avoid reinfection.

Project description:The interaction of clinically relevant microorganisms is the focus of various studies, e.g. the interaction between the pathogenic yeast, Candida albicans, and the bacterium, Pseudomonas aeruginosa and these interactions can alter the outcome of infection, growth dynamics of each species and antimicrobial resistance of pathogens. During infection, both C. albicans and P. aeruginosa can elicit the release arachidonic acid (AA) from host cells membranes through the action of phospholipases. This polyunsaturated fatty acid can be transformed into immune-modulating compounds, termed eicosanoids, by both host-derived and microbial-derived enzymatic reactions. In its free form, AA can affect the growth of both C. albicans and P. aeruginosa, inhibiting the morphogenesis of C. albicans as well as reducing resistance towards antifungal agents. However, the mechanism of this is unknown. Previous studies on the effect of polyunsaturated fatty acids have indicated a possible alteration in plasma membrane organisation and permeability. Our group aimed to address how AA affects C. albicans in both single species biofilms, as well as in polymicrobial biofilms with P. aeruginosa. RNAseq was performed on single and polymicrobial biofilms in the presence and absence of a sub-inhibitory (100 µM) concentration of AA. Differential expression was determined between C. albicans single species biofilms in the presence and absence of AA. Secondly, the influence of co-incubation of C. albicans with P. aeruginosa in the absence of AA was evaluated to identify novel facets of interaction not previously identified, and to establish a baseline to determine the effect of AA on C. albicans in polymicrobial biofilms. Lastly, the effect of AA on C. albicans in polymicrobial biofilms was determined through comparison with polymicrobial biofilms in the absence of AA. This study provides a comprehensive analysis of the effect of AA and both co-incubation of C. albicans with P. aeruginosa focused on the transcriptome.

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Flexible survival strategies of Pseudomonas aeruginosa in biofilms result in increased fitness compared with Candida albicans.

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Flexible survival strategies of Pseudomonas aeruginosa in biofilms result in increased fitness compared with Candida albicans.

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