Fungal biofilm architecture produces hypoxic microenvironments that drive antifungal resistance

Abstract

Human fungal infections may fail to respond to contemporary antifungal therapies in vivo despite in vitro fungal isolate drug susceptibility. Such a discrepancy between in vitro antimicrobial susceptibility and in vivo treatment outcomes is partially explained by microbes adopting a drug-resistant biofilm mode of growth during infection. The filamentous fungal pathogen Aspergillus fumigatus forms biofilms in vivo, and during biofilm growth it has reduced susceptibility to all three classes of contemporary antifungal drugs. Specific features of filamentous fungal biofilms that drive antifungal drug resistance remain largely unknown. In this study, we applied a fluorescence microscopy approach coupled with transcriptional bioreporters to define spatial and temporal oxygen gradients and single-cell metabolic activity within A. fumigatus biofilms. Oxygen gradients inevitably arise during A. fumigatus biofilm maturation and are both critical for, and the result of, A. fumigatus late-stage biofilm architecture. We observe that these self-induced hypoxic microenvironments not only contribute to filamentous fungal biofilm maturation but also drive resistance to antifungal treatment. Decreasing oxygen levels toward the base of A. fumigatus biofilms increases antifungal drug resistance. Our results define a previously unknown mechanistic link between filamentous fungal biofilm physiology and contemporary antifungal drug resistance. Moreover, we demonstrate that drug resistance mediated by dynamic oxygen gradients, found in many bacterial biofilms, also extends to the fungal kingdom. The conservation of hypoxic drug-resistant niches in bacterial and fungal biofilms is thus a promising target for improving antimicrobial therapy efficacy.

Aspergillus nidulans biofilm formation modifies cellular architecture and enables light-activated autophagy

“…With regards to microbial infections, the physiological state of static cells impacts how pathogens respond to drug treatment. For example, fungal biofilm cells generate their own microenvironments and resistance to antifungal treatments (Desai et al, 2014;Kaur and Singh, 2014;Kowalski et al, 2020). On the more positive side, solid state fungal biofilms can be the preferred mode of growth in fungal driven fermentations, as well as production of enzymes, organic acids, and other bioactive compounds (Gutierrez-Correa et al, 2012;Park et al, 2017).…”

A heterogeneously expressed gene family modulates biofilm architecture and hypoxic growth ofAspergillus fumigatus

“…The architecture of the microbial biofilm is dependent on the organism, the surface, and the exogenous environment (52). Specific biofilm architectures have been associated with tolerance to desiccation and antibiotics (53–55), phage resistance (56), and predation evasion (57). Examples of biofilm architecture for bacterial biofilms include the formation of pillars and mushroomlike structures (52, 58, 59).…”

A biocompatible dual-AIEgen system without spectral overlap for quantitation of microbial viability and monitoring of biofilm formation

“…This was attributed to the natural life cycle of fungi cells. 27 In the third panel of Fig. 5A-C, merged images of DCQA and TPE-2BA were presented.…”

“…Biofilm is that aggregates of microorganisms in which cells are frequently embedded in a self-produced matrix of extracellular polymeric substances (EPS) that are adherent to each other and/or a surface. [25][26][27][28][29] In microorganism world, the aggregated style is more common but complicated, and lack of enough understanding. As a biofilm contains complicated components, such as large numbers of microbes and water-rich matrixs, 28,29 while the ACQ probes tends to form aggregates so that cannot work efficiently at such a microenvironment.…”