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MBio Jun 2022In this study, we investigated the influence of fungal extracellular vesicles (EVs) during biofilm formation and morphogenesis in Candida albicans. Using crystal violet...
In this study, we investigated the influence of fungal extracellular vesicles (EVs) during biofilm formation and morphogenesis in Candida albicans. Using crystal violet staining and scanning electron microscopy (SEM), we demonstrated that C. albicans EVs inhibited biofilm formation . By time-lapse microscopy and SEM, we showed that C. albicans EV treatment stopped filamentation and promoted pseudohyphae formation with multiple budding sites. The ability of C. albicans EVs to regulate dimorphism was further compared to EVs isolated from different C. albicans strains, Saccharomyces cerevisiae, and Histoplasma capsulatum. C. albicans EVs from distinct strains inhibited yeast-to-hyphae differentiation with morphological changes occurring in less than 4 h. EVs from S. cerevisiae and H. capsulatum modestly reduced morphogenesis, and the effect was evident after 24 h of incubation. The inhibitory activity of C. albicans EVs on phase transition was promoted by a combination of lipid compounds, which were identified by gas chromatography-tandem mass spectrometry analysis as sesquiterpenes, diterpenes, and fatty acids. Remarkably, C. albicans EVs were also able to reverse filamentation. Finally, C. albicans cells treated with C. albicans EVs for 24 h lost their capacity to penetrate agar and were avirulent when inoculated into Galleria mellonella. Our results indicate that fungal EVs can regulate yeast-to-hypha differentiation, thereby inhibiting biofilm formation and attenuating virulence. The ability to undergo morphological changes during adaptation to distinct environments is exploited by Candida albicans and has a direct impact on biofilm formation and virulence. Morphogenesis is controlled by a diversity of stimuli, including osmotic stress, pH, starvation, presence of serum, and microbial components, among others. Apart from external inducers, C. albicans also produces autoregulatory substances. Farnesol and tyrosol are examples of quorum-sensing molecules (QSM) released by C. albicans to regulate yeast-to-hypha conversion. Here, we demonstrate that fungal EVs are messengers impacting biofilm formation, morphogenesis, and virulence in C. albicans. The major players exported in C. albicans EVs included sesquiterpenes, diterpenes, and fatty acids. The understanding of how C. albicans cells communicate to regulate physiology and pathogenesis can lead to novel therapeutic tools to combat candidiasis.
Topics: Biofilms; Candida albicans; Extracellular Vesicles; Fatty Acids; Hyphae; Saccharomyces cerevisiae
PubMed: 35420476
DOI: 10.1128/mbio.00301-22 -
Cell Host & Microbe Mar 2019Candida albicans is a gut commensal and opportunistic pathogen. The transition between yeast and invasive hyphae is central to virulence but has unknown functions during...
Candida albicans is a gut commensal and opportunistic pathogen. The transition between yeast and invasive hyphae is central to virulence but has unknown functions during commensal growth. In a mouse model of colonization, yeast and hyphae co-occur throughout the gastrointestinal tract. However, competitive infections of C. albicans homozygous gene disruption mutants revealed an unanticipated, inhibitory role for the yeast-to-hypha morphogenesis program on commensalism. We show that the transcription factor Ume6, a master regulator of filamentation, inhibits gut colonization, not by effects on cell shape, but by activating the expression of a hypha-specific pro-inflammatory secreted protease, Sap6, and a hyphal cell surface adhesin, Hyr1. Like a ume6 mutant, strains lacking SAP6 exhibit enhanced colonization fitness, whereas SAP6-overexpression strains are attenuated in the gut. These results reveal a tradeoff between fungal programs supporting commensalism and virulence in which selection against hypha-specific markers limits the disease-causing potential of this ubiquitous commensal-pathogen.
Topics: Animals; Candida albicans; Cell Adhesion Molecules; Fungal Proteins; Gastrointestinal Tract; Gene Expression Regulation, Fungal; Hyphae; Mice; Peptide Hydrolases; Symbiosis; Transcription Factors; Virulence
PubMed: 30870623
DOI: 10.1016/j.chom.2019.02.008 -
Microbiology Spectrum May 2017The characteristic growth pattern of fungal mycelia as an interconnected network has a major impact on how cellular events operating on a micron scale affect colony... (Review)
Review
The characteristic growth pattern of fungal mycelia as an interconnected network has a major impact on how cellular events operating on a micron scale affect colony behavior at an ecological scale. Network structure is intimately linked to flows of resources across the network that in turn modify the network architecture itself. This complex interplay shapes the incredibly plastic behavior of fungi and allows them to cope with patchy, ephemeral resources, competition, damage, and predation in a manner completely different from multicellular plants or animals. Here, we try to link network structure with impact on resource movement at different scales of organization to understand the benefits and challenges of organisms that grow as connected networks. This inevitably involves an interdisciplinary approach whereby mathematical modeling helps to provide a bridge between information gleaned by traditional cell and molecular techniques or biophysical approaches at a hyphal level, with observations of colony dynamics and behavior at an ecological level.
Topics: Animals; Biological Transport; Biomass; Ecology; Ecosystem; Food; Fungi; Hyphae; Models, Biological; Models, Theoretical; Mycelium; Plants; Soil Microbiology; Water
PubMed: 28524023
DOI: 10.1128/microbiolspec.FUNK-0033-2017 -
Trends in Microbiology Nov 2020Fungal infections are on the rise due to new medical procedures that have increased the number of immune compromised patients, antibacterial antibiotics that disrupt the... (Review)
Review
Fungal infections are on the rise due to new medical procedures that have increased the number of immune compromised patients, antibacterial antibiotics that disrupt the microbiome, and increased use of indwelling medical devices that provide sites for biofilm formation. Key to understanding the mechanisms of pathogenesis is to determine how fungal morphology impacts virulence strategies. For example, small budding cells use very different strategies to disseminate compared with long hyphal filaments. Furthermore, cell morphology must be monitored in the host, as many fungal pathogens change their shape to disseminate into new areas, acquire nutrients, and avoid attack by the immune system. This review describes the shape-shifting alterations in morphogenesis of human fungal pathogens and how they influence virulence strategies.
Topics: Animals; Fungal Proteins; Fungi; Gene Expression Regulation, Fungal; Humans; Hyphae; Mycoses; Virulence
PubMed: 32474010
DOI: 10.1016/j.tim.2020.05.001 -
Microbiology Spectrum Apr 2017Filamentous fungi are a large and ancient clade of microorganisms that occupy a broad range of ecological niches. The success of filamentous fungi is largely due to... (Review)
Review
Filamentous fungi are a large and ancient clade of microorganisms that occupy a broad range of ecological niches. The success of filamentous fungi is largely due to their elongate hypha, a chain of cells, separated from each other by septa. Hyphae grow by polarized exocytosis at the apex, which allows the fungus to overcome long distances and invade many substrates, including soils and host tissues. Hyphal tip growth is initiated by establishment of a growth site and the subsequent maintenance of the growth axis, with transport of growth supplies, including membranes and proteins, delivered by motors along the cytoskeleton to the hyphal apex. Among the enzymes delivered are cell wall synthases that are exocytosed for local synthesis of the extracellular cell wall. Exocytosis is opposed by endocytic uptake of soluble and membrane-bound material into the cell. The first intracellular compartment in the endocytic pathway is the early endosomes, which emerge to perform essential additional functions as spatial organizers of the hyphal cell. Individual compartments within septated hyphae can communicate with each other via septal pores, which allow passage of cytoplasm or organelles to help differentiation within the mycelium. This article introduces the reader to more detailed aspects of hyphal growth in fungi.
Topics: Fungal Proteins; Fungi; Hyphae
PubMed: 28429675
DOI: 10.1128/microbiolspec.FUNK-0034-2016 -
Current Opinion in Microbiology Aug 2009Hypha orientation is an essential aspect of polarised growth and the morphogenesis, spatial ecology and pathogenesis of fungi. The ability to re-orient tip growth in... (Review)
Review
Hypha orientation is an essential aspect of polarised growth and the morphogenesis, spatial ecology and pathogenesis of fungi. The ability to re-orient tip growth in response to environmental cues is critical for colony ramification, the penetration of diverse host tissues and the formation of mating structures. Recent studies have begun to describe the molecular machinery regulating hypha orientation. Calcium signalling, the polarisome Bud1-GTPase module and the Tea cell-end marker proteins of the microtubule cytoskeleton, along with specific kinesins and sterol-rich apical microdomains, are involved in hypha orientation. Mutations that affect these processes generate normal-shaped, growing hyphae that have either abnormal meandering trajectories or attenuated tropic responses. Hyphal tip orientation and tip extension are, therefore, distinct regulatory mechanisms that operate in parallel during filamentous growth, thereby allowing fungi to orchestrate their reproduction in relation to gradients of effectors in their environments.
Topics: Environment; Fungi; Hyphae; Models, Biological; Stress, Physiological
PubMed: 19546023
DOI: 10.1016/j.mib.2009.05.007 -
MSystems Dec 2022The yeast-to-hypha transition is a key virulence attribute of the opportunistic human fungal pathogen Candida albicans, since it is closely tied to infection-associated...
The yeast-to-hypha transition is a key virulence attribute of the opportunistic human fungal pathogen Candida albicans, since it is closely tied to infection-associated processes such as tissue invasion and escape from phagocytes. While the nature of hypha-associated gene expression required for fungal virulence has been thoroughly investigated, potential morphotype-dependent activity of metabolic pathways remained unclear. Here, we combined global transcriptome and metabolome analyses for the wild-type SC5314 and the hypha-defective Δ and ΔΔ strains under three hypha-inducing (human serum, -acetylglucosamine, and alkaline pH) and two yeast-promoting conditions to identify metabolic adaptions that accompany the filamentation process. We identified morphotype-related activities of distinct pathways and a metabolic core signature of 26 metabolites with consistent depletion or enrichment during the yeast-to-hypha transition. Most strikingly, we found a hypha-associated activation of sphingolipid biosynthesis, indicating a connection of this pathway and filamentous growth. Consequently, pharmacological inhibition of this partially fungus-specific pathway resulted in strongly impaired filamentation, verifying the necessity of sphingolipid biosynthesis for proper hypha formation. The reversible switch of Candida albicans between unicellular yeast and multicellular hyphal growth is accompanied by a well-studied hypha-associated gene expression, encoding virulence factors like adhesins, toxins, or nutrient scavengers. The investigation of this gene expression consequently led to fundamental insights into the pathogenesis of this fungus. In this study, we applied this concept to hypha-associated metabolic adaptations and identified morphotype-dependent activities of distinct pathways and a stimulus-independent metabolic signature of hyphae. Most strikingly, we found the induction of sphingolipid biosynthesis as hypha associated and essential for the filamentation of C. albicans. These findings verified the presence of morphotype-specific metabolic traits in the fungus, which appear connected to the fungal virulence. Furthermore, the here-provided comprehensive description of the fungal metabolome will help to foster future research and lead to a better understanding of fungal physiology.
Topics: Humans; Candida albicans; Hyphae; Fungal Proteins; Virulence Factors; Sphingolipids
PubMed: 36264075
DOI: 10.1128/msystems.00539-22 -
Microbiology Spectrum Feb 2022The infection of often results in a grayish appearance with numerous survival structures, microsclerotia, on the plant surface. Past works have studied the development...
The infection of often results in a grayish appearance with numerous survival structures, microsclerotia, on the plant surface. Past works have studied the development of fungal survival structures, sclerotia and microsclerotia, in the Leotiomycetes and Sordariomycetes. However, M. phaseolina belongs to the Dothideomycetes, and it remains unclear whether the mechanism of microsclerotia formation remains conserved among these phylogenetic clades. This study applied RNA-sequencing (RNA-Seq) to profile gene expressions at four stages of microsclerotia formation, and the results suggested that reactive oxygen species (ROS)-related functions were significantly different between the microsclerotia stages and the hyphal stage. Microsclerotia formation was reduced in the plates amended with antioxidants such as ascorbic acid, dithiothreitol (DTT), and glutathione. Surprisingly, DTT drastically scavenged HO, but the microsclerotia amount remained similar to the treatment of ascorbic acid and glutathione that both did not completely eliminate HO. This observation suggested the importance of [Formula: see text] over HO in initiating microsclerotia formation. To further validate this hypothesis, the superoxide dismutase 1 (SOD1) inhibitor diethyldithiocarbamate trihydrate (DETC) and HO were tested. The addition of DETC resulted in the accumulation of endogenous [Formula: see text] and more microsclerotia formation, but the treatment of HO did not. The expression of SOD1 genes were also found to be upregulated in the hyphae to the microsclerotia stage, which suggested a higher endogenous [Formula: see text] stress presented in these stages. In summary, this study not only showed that the ROS stimulation remained conserved for initiating microsclerotia formation of M. phaseolina but also highlighted the importance of [Formula: see text] in initiating the hyphal differentiation to microsclerotia formation. Reactive oxygen species (ROS) have been proposed as the key stimulus for sclerotia development by studying fungal systems such as Sclerotinia sclerotiorum, and the theory has been adapted for microsclerotia development in Verticillium dahliae and Nomuraea rileyi. While many studies agreed on the association between (micro)sclerotia development and the ROS pathway, which ROS type, superoxide ([Formula: see text]) or hydrogen peroxide (HO), plays a major role in initiating hyphal differentiation to the (micro)sclerotia formation remains controversial, and literature supporting either [Formula: see text] or HO can be found. This study confirmed the association between ROS and microsclerotia formation for the charcoal rot fungus Macrophomina phaseolina. Moreover, the accumulation of [Formula: see text] but not HO was found to induce higher density of microsclerotia. By integrating transcriptomic and phenotypic assays, this study presented the first conclusive case for M. phaseolina that [Formula: see text] is the main ROS stimulus in determining the amount of microsclerotia formation.
Topics: Ascomycota; Cell Differentiation; Gene Expression; Glutathione; Hydrogen Peroxide; Hyphae; Phylogeny; Plant Diseases; Reactive Oxygen Species; Superoxides
PubMed: 35080446
DOI: 10.1128/spectrum.02084-21 -
Microbiology Spectrum Apr 2017The growth and development of most fungi take place on a two-dimensional surface or within a three-dimensional matrix. The fungal sense of touch is therefore critical... (Review)
Review
The growth and development of most fungi take place on a two-dimensional surface or within a three-dimensional matrix. The fungal sense of touch is therefore critical for fungi in the interpretation of their environment and often signals the switch to a new developmental state. Contact sensing, or thigmo-based responses, include thigmo differentiation, such as the induction of invasion structures by plant pathogens in response to topography; thigmonasty, where contact with a motile prey rapidly triggers its capture; and thigmotropism, where the direction of hyphal growth is guided by physical features in the environment. Like plants and some bacteria, fungi grow as walled cells. Despite the well-demonstrated importance of thigmo responses in numerous stages of fungal growth and development, it is not known how fungal cells sense contact through the relatively rigid structure of the cell wall. However, while sensing mechanisms at the molecular level are not entirely understood, the downstream signaling pathways that are activated by contact sensing are being elucidated. In the majority of cases, the response to contact is complemented by chemical cues and both are required, either sequentially or simultaneously, to elicit normal developmental responses. The importance of a sense of touch in the lifestyles and development of diverse fungi is highlighted in this review, and the candidate molecular mechanisms that may be involved in fungal contact sensing are discussed.
Topics: Cell Fusion; Cell Wall; Environment; Fungi; Host-Pathogen Interactions; Humans; Hyphae; Ion Channels; Life Style; Mechanotransduction, Cellular; Osmotic Pressure; Plant Diseases; Plants; Sensation; Signal Transduction; Symbiosis
PubMed: 28884680
DOI: 10.1128/microbiolspec.FUNK-0040-2016 -
MBio Apr 2023Nrg1 is a repressor of hypha formation and hypha-associated gene expression in the fungal pathogen Candida albicans. It has been well studied in the genetic background...
Nrg1 is a repressor of hypha formation and hypha-associated gene expression in the fungal pathogen Candida albicans. It has been well studied in the genetic background of the type strain SC5314. Here, we tested Nrg1 function in four other diverse clinical isolates through an analysis of Δ/Δ mutants, with SC5314 included as a control. In three strains, Δ/Δ mutants unexpectedly produced aberrant hyphae under inducing conditions, as assayed by microscopic observation and endothelial cell damage. The Δ/Δ mutant of strain P57055 had the most severe defect. We examined gene expression features under hypha-inducing conditions by RNA-sequencing (RNA-Seq) for the SC5314 and P57055 backgrounds. The SC5314 Δ/Δ mutant expressed six hypha-associated genes at reduced levels compared with wild-type SC5314. The P57055 Δ/Δ mutant expressed 17 hypha-associated genes at reduced levels compared with wild-type P57055, including , , and . These findings indicate that Nrg1 has a positive role in hypha-associated gene expression and that this role is magnified in strain P57055. Remarkably, the same hypha-associated genes affected by the Δ/Δ mutation in strain P57055 were also naturally expressed at lower levels in wild-type P57055 than those in wild-type SC5314. Our results suggest that strain P57055 is defective in a pathway that acts in parallel with Nrg1 to upregulate the expression of several hypha-associated genes. Hypha formation is a central virulence trait of the fungal pathogen Candida albicans. Control of hypha formation has been studied in detail in the type strain but not in other diverse C. albicans clinical isolates. Here, we show that the hyphal repressor Nrg1 has an unexpected positive role in hypha formation and hypha-associated gene expression, as revealed by the sensitized P57055 strain background. Our findings indicate that reliance on a single type strain limits understanding of gene function and illustrate that strain diversity is a valuable resource for C. albicans molecular genetic analysis.
Topics: Candida albicans; Hyphae; Fungal Proteins; Endothelial Cells; Gene Expression Regulation, Fungal
PubMed: 36883818
DOI: 10.1128/mbio.00134-23