Coordination of fungal biofilm development by extracellular vesicle cargo

Abstract

The fungal pathogen Candida albicans can form biofilms that protect it from drugs and the immune system. The biofilm cells release extracellular vesicles (EVs) that promote extracellular matrix formation and resistance to antifungal drugs. Here, we define functions for numerous EV cargo proteins in biofilm matrix assembly and drug resistance, as well as in fungal cell adhesion and dissemination. We use a machine-learning analysis of cargo proteomic data from mutants with EV production defects to identify 63 candidate gene products for which we construct mutant and complemented strains for study. Among these, 17 mutants display reduced biofilm matrix accumulation and antifungal drug resistance. An additional subset of 8 cargo mutants exhibit defects in adhesion and/or dispersion. Representative cargo proteins are shown to function as EV cargo through the ability of exogenous wild-type EVs to complement mutant phenotypic defects. Most functionally assigned cargo proteins have roles in two or more of the biofilm phases. Our results support that EVs provide community coordination throughout biofilm development in C. albicans.

Insight Into the Properties and Immunoregulatory Effect of Extracellular Vesicles Produced by Candida glabrata, Candida parapsilosis, and Candida tropicalis Biofilms

“…In the case of C. albicans biofilm, it has been shown that vesicles produced by cells in the biofilm contribute to the formation of the biofilm matrix and the occurrence of fluconazole resistance ( Zarnowski et al., 2018 ; Zarnowski et al., 2021 ). Therefore, in this study we examined whether EVs might influence formation of biofilm by C. tropicalis, which of the three tested Candida species produced the most stable biofilm and was susceptible to the applied antifungal drugs ‒ fluconazole (FLU) and caspofungin (CASP) ( Figure 5 ).…”

“…EVs and their content might participate in the interaction between fungal pathogens and human cells during infection development, inducing also immune system response ( Gil-Bona et al., 2015 ; de Toledo Martins et al., 2018 ). Moreover, Candida EVs might also play an important role in the communication between cells of the same species forming a complex community, influencing fungal cell adhesion to different surfaces, formation of biofilm structures, and further development and propagation of infection ( Zarnowski et al., 2018 ; Zarnowski et al., 2021 ). In addition, the communication through EV release between Candida yeasts and other microorganisms living in the same niche might be crucial in the development of multispecies infections.…”

“…Proteins carried by vesicles released by C. albicans biofilm might be involved in the production of the biofilm matrix through their enzymatic activity, and EVs might directly provide other matrix-building components like lipids and polysaccharides—glucan and mannan—thus contributing to the resistance of C. albicans biofilm to fluconazole by entrapping the antifungal drug within the matrix structure ( Taff et al., 2012 ; Zarnowski et al., 2018 ; Zhao et al., 2021 ). Moreover, C. albicans biofilm-derived EVs play a role not only in biofilm matrix production and in reducing biofilm susceptibility to antifungals, but they are also involved in other stages of biofilm formation, like fungal cell adhesion and biofilm dispersion ( Zarnowski et al., 2021 ). Hence, they contribute strongly and in multiple ways to the creation of this complex microbial community.…”

Extracellular Vesicles From Paracoccidioides brasiliensis Can Induce the Expression of Fungal Virulence Traits In Vitro and Enhance Infection in Mice

“…The number and variety of the reported fungal EV cargo has increased lately with the interest to study these structures. EVs are likely to participate in cell wall remodeling ( Longo et al., 2014 ; Nimrichter et al., 2016 ; Zhao et al., 2019 ; reviewed in Rizzo et al., 2020 ) as well as in the synthesis of Candida biofilms ( Zarnowski et al., 2018 ; Zarnowski et al., 2021 ). They participate in the synthesis of the main virulence factor in Cryptococcus , which is the high molecular weight glucuronoxylomannose component of the capsule ( Rodrigues et al., 2008 ; Reis et al., 2019 ; reviewed in de Oliveira et al, 2020 ; Rizzo et al., 2020 ).…”

Recent Progress of Exosome Isolation and Peptide Recognition-Guided Strategies for Exosome Research

“…Exosomes were once considered to be the waste products of cells in the original research. Nowadays, more and more studies have shown that exosomes play important roles in organisms, such as cell-to-cell communication ( Ruhland et al, 2020 ; Schneider et al, 2021 ), immune response ( Kalluri and LeBleu, 2020 ; Su et al, 2020 ), cell growth and differentiation ( Yin et al, 2021 ; Zarnowski et al, 2021 ), as well as molecular transport ( Zhu Q. et al, 2021 ). Crucially, the concentration and phenotype of exosomes have been proved to reflect the state of their parental cells and associate with the occurrence and development of various diseases, such as cancers ( Jiang et al, 2021 ), infectious diseases ( Ning et al, 2021 ; Xie et al, 2021 ), metabolic, and cardiovascular diseases ( Kalluri and LeBleu, 2020 ).…”