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Wakade RS, Wellington M, Krysan DJ. Temporal dynamics of Candida albicans morphogenesis and gene expression reveals distinctions between in vitro and in vivo filamentation. mSphere 2024; 9:e0011024. [PMID: 38501830 PMCID: PMC11036811 DOI: 10.1128/msphere.00110-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Accepted: 02/29/2024] [Indexed: 03/20/2024] Open
Abstract
Candida albicans is a common human fungal pathogen that is also a commensal of the oral cavity and gastrointestinal tract. C. albicans pathogenesis is linked to its transition from budding yeast to filamentous morphologies including hyphae and pseudohyphae. The centrality of this virulence trait to C. albicans pathobiology has resulted in extensive characterization of a wide range of factors associated with filamentation with a strong focus on transcriptional regulation. The vast majority of these experiments have used in vitro conditions to induce the yeast-to-filament transition. Taking advantage of in vivo approaches to quantitatively characterize both morphology and gene expression during filamentation during mammalian infection, we have investigated the dynamics of these two aspects of filamentation in vivo and compared them to in vitro filament induction with "host-like" tissue culture media supplemented with serum at mammalian body temperature. Although filamentation shares many common features in the two conditions, we have found two significant differences. First, alternative carbon metabolism genes are expressed early during in vitro filamentation and late in vivo, suggesting significant differences in glucose availability. Second, C. albicans begins a hyphae-to-yeast transition after 4-h incubation while we find little evidence of hyphae-to-yeast transition in vivo up to 24 h post-infection. We show that the low rate of in vivo hyphae-to-yeast transition is likely due to the very low expression of PES1, a key driver of lateral yeast in vitro and that heterologous expression of PES1 is sufficient to trigger lateral yeast formation in vivo.IMPORTANCECandida albicans filamentation is correlated with virulence and is an intensively studied aspect of C. albicans biology. The vast majority of studies on C. albicans filamentation are based on in vitro induction of hyphae and pseudohyphae. Here we used an in vivo filamentation assay and in vivo expression profiling to compare the tempo of morphogenesis and gene expression between in vitro and in vivo filamentation. Although the hyphal gene expression profile is induced rapidly in both conditions, it remains stably expressed over a 12-h time course in vivo while it peaks after 4 h in vitro and is reduced. This reduced hyphal gene expression in vitro correlates with reduced hyphae and increased hyphae-to-yeast transition. By contrast, there is little evidence of hyphae-to-yeast transition in vivo.
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Affiliation(s)
- Rohan S. Wakade
- Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Melanie Wellington
- Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Damian J. Krysan
- Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
- Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
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McCrory C, Verma J, Tucey TM, Turner R, Weerasinghe H, Beilharz TH, Traven A. The short-chain fatty acid crotonate reduces invasive growth and immune escape of Candida albicans by regulating hyphal gene expression. mBio 2023; 14:e0260523. [PMID: 37929941 PMCID: PMC10746253 DOI: 10.1128/mbio.02605-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Accepted: 10/02/2023] [Indexed: 11/07/2023] Open
Abstract
Microbes are exposed to nutritional and stress challenges in their environmental and host niches. To rise to these challenges, they regulate transcriptional programs that enable cellular adaptation. For instance, metabolite concentrations regulate post-translational modifications of chromatin, such as histone acetylation. In this way, metabolic signals are integrated with transcription. Over the last decade, several histone acylations have been discovered, including histone crotonylation. Their roles in microbial biology, environmental adaptation, and microbe-host interactions are incompletely defined. Here we show that the short-chain fatty acid crotonate, which is used to study histone crotonylation, changes cell morphology and immune interactions of Candida albicans. Crotonate reduces invasive hyphal morphogenesis of C. albicans within macrophages, thereby delaying macrophage killing and pathogen escape, as well as reducing inflammatory cytokine maturation. Crotonate's ability to reduce hyphal growth is environmentally contingent and pronounced within macrophages. Moreover, crotonate is a stronger hyphal inhibitor than butyrate under the conditions that we tested. Crotonate causes increased histone crotonylation in C. albicans under hyphal growth conditions and reduces transcription of hyphae-induced genes in a manner that involves the Nrg1 repressor pathway. Increasing histone acetylation by histone deacetylase inhibition partially rescues hyphal growth and gene transcription in the presence of crotonate. These results indicate that histone crotonylation might compete with acetylation in the regulation of hyphal morphogenesis. Based on our findings, we propose that diverse acylations of histones (and likely also non-histone proteins) enable C. albicans to respond to environmental signals, which in turn regulate its cell morphology and host-pathogen interactions.IMPORTANCEMacrophages curtail the proliferation of the pathogen Candida albicans within human body niches. Within macrophages, C. albicans adapts its metabolism and switches to invasive hyphal morphology. These adaptations enable fungal growth and immune escape by triggering macrophage lysis. Transcriptional programs regulate these metabolic and morphogenetic adaptations. Here we studied the roles of chromatin in these processes and implicate lysine crotonylation, a histone mark regulated by metabolism, in hyphal morphogenesis and macrophage interactions by C. albicans. We show that the short-chain fatty acid crotonate increases histone crotonylation, reduces hyphal formation within macrophages, and slows macrophage lysis and immune escape of C. albicans. Crotonate represses hyphal gene expression, and we propose that C. albicans uses diverse acylation marks to regulate its cell morphology in host environments. Hyphal formation is a virulence property of C. albicans. Therefore, a further importance of our study stems from identifying crotonate as a hyphal inhibitor.
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Affiliation(s)
- Christopher McCrory
- Department of Biochemistry and Molecular Biology and Infection Program, Biomedicine Discovery Institute, Monash University, Clayton, Australia
- Centre to Impact AMR, Monash University, Clayton, Australia
| | - Jiyoti Verma
- Department of Biochemistry and Molecular Biology and Infection Program, Biomedicine Discovery Institute, Monash University, Clayton, Australia
| | - Timothy M. Tucey
- Department of Biochemistry and Molecular Biology and Infection Program, Biomedicine Discovery Institute, Monash University, Clayton, Australia
| | - Rachael Turner
- Department of Biochemistry and Molecular Biology and Stem Cells and Development Program, Biomedicine Discovery Institute, Monash University, Clayton, Australia
| | - Harshini Weerasinghe
- Department of Biochemistry and Molecular Biology and Infection Program, Biomedicine Discovery Institute, Monash University, Clayton, Australia
- Centre to Impact AMR, Monash University, Clayton, Australia
| | - Traude H. Beilharz
- Department of Biochemistry and Molecular Biology and Infection Program, Biomedicine Discovery Institute, Monash University, Clayton, Australia
- Department of Biochemistry and Molecular Biology and Stem Cells and Development Program, Biomedicine Discovery Institute, Monash University, Clayton, Australia
| | - Ana Traven
- Department of Biochemistry and Molecular Biology and Infection Program, Biomedicine Discovery Institute, Monash University, Clayton, Australia
- Centre to Impact AMR, Monash University, Clayton, Australia
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Baltussen TJ, van Rhijn N, Coolen JP, Dijksterhuis J, Verweij PE, Bromley MJ, Melchers WJ. The C 2H 2 transcription factor SltA is required for germination and hyphal development in Aspergillus fumigatus. mSphere 2023; 8:e0007623. [PMID: 37260230 PMCID: PMC10449517 DOI: 10.1128/msphere.00076-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 03/23/2023] [Indexed: 06/02/2023] Open
Abstract
Germination of inhaled Aspergillus fumigatus conidia is a necessary sequitur for infection. Germination of conidia starts with the breaking of dormancy, which is initiated by an increase of the cellular perimeter in a process termed isotropic growth. This swelling phase is followed by polarized growth, resulting in the formation of a germ tube. The multinucleate tubular cells exhibit tip growth from the hyphae, after which lateral branches emerge to form the mycelial network. The regulatory mechanisms governing conidial germination are not well defined. In this study, we identified a novel role for the transcription factor SltA in the orchestration of germination and hyphal development. Conidia lacking sltA fail to appropriately regulate isotropic growth and begin to swell earlier and subsequently switch to polarized growth faster. Additionally, hyphal development is distorted in a ∆sltA isolate as hyphae are hyper-branching and wider, and show branching at the apical tip. ∆sltA conidia are more tolerant to cell wall stressors on minimal medium compared to the wild-type (WT) strain. A transcriptome analysis of different stages of early growth was carried out to assess the regulatory role of SltA. Null mutants generated for three of the most dysregulated genes showed rapid germ tube emergence. Distinct from the phenotype observed for ∆sltA, conidia from these strains lacked defects in isotropic growth, but switched to polarized growth faster. Here, we characterize and describe several genes in the regulon of SltA, highlighting the complex nature of germination.IMPORTANCEAspergillus fumigatus is the main human fungal pathogen causing aspergillosis. For this fungus, azoles are the most commonly used antifungal drugs for treatment of aspergillosis. However, the prevalence of azole resistance is alarmingly increasing and linked with elevated mortality. Germination of conidia is crucial within its asexual life cycle and plays a critical role during the infection in the human host. Precluding germination could be a promising strategy considering the role of germination in Aspergillus spp. pathogenicity. Here, we identify a novel role for SltA in appropriate maintenance of dormancy, germination, and hyphal development. Three genes in the regulon of SltA were also essential for appropriate germination of conidia. With an expanding knowledge of germination and its different morphotypes, more advances can be made toward potential anti-germination targets for therapy.
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Affiliation(s)
- Tim J.H. Baltussen
- Department of Medical Microbiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Norman van Rhijn
- Manchester Fungal Infection Group, Division of Evolution, Infection and Genomics, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Jordy P.M. Coolen
- Department of Medical Microbiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Jan Dijksterhuis
- Westerdijk Fungal Biodiversity Institute, Utrecht, The Netherlands
| | - Paul E. Verweij
- Department of Medical Microbiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Michael J. Bromley
- Manchester Fungal Infection Group, Division of Evolution, Infection and Genomics, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Willem J.G. Melchers
- Department of Medical Microbiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
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Mao Y, Solis NV, Filler SG, Mitchell AP. Functional Dichotomy for a Hyphal Repressor in Candida albicans. mBio 2023; 14:e0013423. [PMID: 36883818 PMCID: PMC10127614 DOI: 10.1128/mbio.00134-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Accepted: 02/20/2023] [Indexed: 03/09/2023] Open
Abstract
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 nrg1Δ/Δ mutants, with SC5314 included as a control. In three strains, nrg1Δ/Δ mutants unexpectedly produced aberrant hyphae under inducing conditions, as assayed by microscopic observation and endothelial cell damage. The nrg1Δ/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 nrg1Δ/Δ mutant expressed six hypha-associated genes at reduced levels compared with wild-type SC5314. The P57055 nrg1Δ/Δ mutant expressed 17 hypha-associated genes at reduced levels compared with wild-type P57055, including IRF1, RAS2, and ECE1. 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 nrg1Δ/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. IMPORTANCE 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.
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Affiliation(s)
- Yinhe Mao
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
| | - Norma V. Solis
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, USA
| | - Scott G. Filler
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, USA
- David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Aaron P. Mitchell
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
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A Carevic T, Stojkovic D, Ivanov M. Plant Flavonoids as Reservoirs of Therapeutics against Microbial Virulence Traits: A Comprehensive Review Update. Curr Pharm Des 2023; 29:914-927. [PMID: 37069709 DOI: 10.2174/1381612829666230413085029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 01/31/2023] [Accepted: 01/31/2023] [Indexed: 04/19/2023]
Abstract
Flavonoids are secondary metabolites abundantly present in plants and, in most cases, essential contributors to plants bioactivity. They have been studied so far for a range of possible health-beneficial effects, including antioxidant, cardioprotective, and cytotoxic. Therefore, there are data on the antimicrobial potential of a significant number of flavonoids. However, less is known regarding their antivirulence traits. Trending antimicrobial research worldwide has pointed out the promising effects of antimicrobial strategies based on the antivirulence principle, so this review aims to present the newest research regarding the antivirulence effects of flavonoids. Articles on antivirulence flavonoids published from 2015 until now were selected. A range of molecules from this class has been studied up to date, with the most abundant data for quercetin and myricetin, while the most studied organism is Pseudomonas aeruginosa. The antivirulence attributes studied included antibiofilm assessment, followed by data on the inhibition of virulence pigments (pyocyanin, violacein, and staphyloxanthin) and virulence enzyme production (such as sortase A and elastase). Less information is collected on the inhibition of morphological transition, motility, and molecular mechanisms underlying the antivirulence properties of flavonoids and in vivo research. Flavonoids are a group of compounds with a wide range of antivirulence traits and might be further developed into essential parts of novel antimicrobial strategies.
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Affiliation(s)
- Tamara A Carevic
- Department of Plant Physiology, Institute for Biological Research "Siniša Stanković"-National Institute of Republic of Serbia, University of Belgrade, Bulevar despota Stefana 142, Belgrade 11000, Serbia
| | - Dejan Stojkovic
- Department of Plant Physiology, Institute for Biological Research "Siniša Stanković"-National Institute of Republic of Serbia, University of Belgrade, Bulevar despota Stefana 142, Belgrade 11000, Serbia
| | - Marija Ivanov
- Department of Plant Physiology, Institute for Biological Research "Siniša Stanković"-National Institute of Republic of Serbia, University of Belgrade, Bulevar despota Stefana 142, Belgrade 11000, Serbia
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Garbe E, Gerwien F, Driesch D, Müller T, Böttcher B, Gräler M, Vylkova S. Systematic Metabolic Profiling Identifies De Novo Sphingolipid Synthesis as Hypha Associated and Essential for Candida albicans Filamentation. mSystems 2022; 7:e0053922. [PMID: 36264075 DOI: 10.1128/msystems.00539-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
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 hgc1Δ and cph1Δefg1Δ strains under three hypha-inducing (human serum, N-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 de novo 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 de novo sphingolipid biosynthesis for proper hypha formation. IMPORTANCE 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 de novo 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.
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Mao Y, Solis NV, Sharma A, Cravener MV, Filler SG, Mitchell AP. Use of the Iron-Responsive RBT5 Promoter for Regulated Expression in Candida albicans. mSphere 2022; 7:e0030522. [PMID: 35862800 PMCID: PMC9429880 DOI: 10.1128/msphere.00305-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 07/03/2022] [Indexed: 11/20/2022] Open
Abstract
Engineered conditional gene expression is used in appraisal of gene function and pathway relationships. For pathogens like the fungus Candida albicans, conditional expression systems are most useful if they are active in the infection environment and if they can be utilized in multiple clinical isolates. Here, we describe such a system. It employs the RBT5 promoter and can be implemented with a few PCRs. We validated the system with RBT5 promoter fusions to two genes that promote filamentation and polarized growth, UME6 and HGC1, and with efg1Δ/Δ mutants, which are defective in an activator of filamentous growth. An RBT5 promoter fusion to either gene enabled filamentous growth of an efg1Δ/Δ mutant of strain SC5314 in iron-limited media, including RPMI with serum and yeast extract-peptone-dextrose with bathophenanthrolinedisulfonic acid. The RBT5-UME6 fusion promoted filamentation of efg1Δ/Δ mutants in RPMI with serum of four other clinical C. albicans isolates as well. In a mouse model of disseminated candidiasis, the RBT5-UME6 fusion promoted filamentation of the SC5314 efg1Δ/Δ mutant in kidney tissue, an indication that the RBT5 promoter is active in the iron-limited host environment. The RBT5 promoter expands the conditional expression toolkit for C. albicans genetics. IMPORTANCE Genetic strategies have been vital for mechanistic analysis of biological processes. Here, we describe a genetic tool for the fungal pathogen Candida albicans.
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Affiliation(s)
- Yinhe Mao
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
| | - Norma V. Solis
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, USA
| | - Anupam Sharma
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
| | - Max V. Cravener
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
| | - Scott G. Filler
- Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, USA
| | - Aaron P. Mitchell
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
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Salama OE, Gerstein AC. Differential Response of Candida Species Morphologies and Isolates to Fluconazole and Boric Acid. Antimicrob Agents Chemother 2022;:e0240621. [PMID: 35446135 DOI: 10.1128/aac.02406-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Candida albicans is the most prevalent cause of vulvovaginal candidiasis ("yeast infection" or VVC) and recurrent vulvovaginal candidiasis (RVVC), although the incidence of non-albicans yeast species is increasing. The azole fluconazole is the primary antifungal drug used to treat RVVC, yet isolates from some species have intrinsic resistance to fluconazole, and recurrent infection can occur even with fluconazole-susceptible populations. The second-line broad-spectrum antimicrobial drug, boric acid, is an alternative treatment that has been found to successfully treat complicated VVC infections. Far less is known about how boric acid inhibits growth of yeast isolates in different morphologies compared to fluconazole. We found significant differences in drug resistance and drug tolerance (the ability of a subpopulation to grow slowly in high levels of drug) between C. albicans, Candida glabrata, and Candida parapsilosis isolates, with the specific relationships dependent on both drug and phenotype. Population-level variation for both susceptibility and tolerance was broader for fluconazole than boric acid in all species. Unlike fluconazole, which neither prevented hyphal formation nor disrupted mature biofilms, boric acid inhibited C. albicans hyphal formation and reduced mature biofilm biomass and metabolic activity in all isolates in a dose-dependent manner. Variation in planktonic response did not generally predict biofilm phenotypes for either drug. Overall, our findings illustrate that boric acid is broadly effective at inhibiting growth across many isolates and morphologies, which could explain why it is an effective treatment for RVVC.
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Abstract
Candida albicans is one of the most common pathogens of humans. One important virulence factor of C. albicans is its ability to form elongated hyphae that can invade host tissues and cause disseminated infections. Here, we show the effect of different physiologically relevant temperatures and common antifungal drugs on the growth and mechanical properties of C. albicans hyphae using atomic force microscopy. We demonstrate that minor temperature fluctuations within the normal range can have profound effects on hyphal cell growth and that different antifungal drugs impact hyphal cell stiffness and adhesion in different ways. Candida albicans is an opportunistic fungal pathogen of humans known for its ability to cause a wide range of infections. One major virulence factor of C. albicans is its ability to form hyphae that can invade host tissues and cause disseminated infections. Here, we introduce a method based on atomic force microscopy to investigate C. albicans hyphae in situ on silicone elastomer substrates, focusing on the effects of temperature and antifungal drugs. Hyphal growth rates differ significantly for measurements performed at different physiologically relevant temperatures. Furthermore, it is found that fluconazole is more effective than caspofungin in suppressing hyphal growth. We also investigate the effects of antifungal drugs on the mechanical properties of hyphal cells. An increase in Young’s modulus and a decrease in adhesion force are observed in hyphal cells subjected to caspofungin treatment. Young’s moduli are not significantly affected following treatment with fluconazole; the adhesion force, however, increases. Overall, our results provide a direct means of observing the effects of environmental factors and antifungal drugs on C. albicans hyphal growth and mechanics with high spatial resolution. IMPORTANCECandida albicans is one of the most common pathogens of humans. One important virulence factor of C. albicans is its ability to form elongated hyphae that can invade host tissues and cause disseminated infections. Here, we show the effect of different physiologically relevant temperatures and common antifungal drugs on the growth and mechanical properties of C. albicans hyphae using atomic force microscopy. We demonstrate that minor temperature fluctuations within the normal range can have profound effects on hyphal cell growth and that different antifungal drugs impact hyphal cell stiffness and adhesion in different ways.
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Bedekovic T, Agnew E, Brand AC. Rsr1 Palmitoylation and GTPase Activity Status Differentially Coordinate Nuclear, Septin, and Vacuole Dynamics in Candida albicans. mBio 2020; 11:e01666-20. [PMID: 33051364 DOI: 10.1128/mBio.01666-20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Directional growth and tissue invasion by hyphae of the pathogenic fungus, Candida albicans, are disrupted by deletion of the small GTPase, Rsr1, which localizes Cdc42 and its kinase, Cla4, to the site of polarized growth. We investigated additional abnormalities observed in rsr1Δ hyphae, including vacuole development, cytoplasm inheritance, mitochondrial morphology, septin ring organization, nuclear division and migration, and branching frequency, which together demonstrate a fundamental role for Rsr1 in cellular organization. Rsr1 contains a C-terminal CCAAX box, which putatively undergoes both reversible palmitoylation and farnesylation for entry into the secretory pathway. We expressed variants of Rsr1 with mutated C244 or C245, or which lacked GTPase activity (Rsr1K16N and Rsr1G12V), in the rsr1Δ background and compared the resulting phenotypes with those of mutants lacking Bud5 (Rsr1 GEF), Bud2 (Rsr1 GAP), or Cla4. Bud5 was required only for cell size and bud site selection in yeast, suggesting there are alternative activators for Rsr1 in hyphae. Septin ring and vacuole dynamics were restored by expression of unpalmitoylated Rsr1C244S, which localized to endomembranes, but not by cytoplasmic Rsr1C245A or GTP/GDP-locked Rsr1, suggesting Rsr1 functions at intracellular membranes in addition to the plasma membrane. Rsr1K16N or cytoplasmic Rsr1C245A restored normal nuclear division but not septin ring or vacuole dynamics. Rsr1-GDP therefore plays a specific role in suppressing START, which can be signaled from the cytosol. Via differential palmitoylation and activity states, Rsr1 operates at diverse cell sites to orchestrate proper nuclear division and inheritance during constitutive polarized growth. As cla4Δ phenocopied rsr1Δ, it is likely these functions involve Cdc42-Cla4 activity.IMPORTANCE Understanding how single eukaryotic cells self-organize to replicate and migrate is relevant to health and disease. In the fungal pathogen, Candida albicans, the small GTPase, Rsr1, guides the directional growth of hyphae that invade human tissue during life-threatening infections. Rsr1 is a Ras-like GTPase and a homolog of the conserved Rap1 subfamily, which directs migration in mammalian cells. Research into how this single GTPase delivers complex intracellular patterning is challenging established views of GTPase regulation, trafficking, and interaction. Here, we show that Rsr1 directly and indirectly coordinates the spatial and temporal development of key intracellular macrostructures, including septum formation and closure, vacuole dynamics, and nuclear division and segregation, as well as whole-cell morphology by determining branching patterns. Furthermore, we categorize these functions by differential Rsr1 localization and activity state and provide evidence to support the emerging view that the cytosolic pool of Ras-like GTPases is functionally active.
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Salvatori O, Kumar R, Metcalfe S, Vickerman M, Kay JG, Edgerton M. Bacteria Modify Candida albicans Hypha Formation, Microcolony Properties, and Survival within Macrophages. mSphere 2020; 5:e00689-20. [PMID: 32759336 DOI: 10.1128/mSphere.00689-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Candida albicans is the predominant fungus colonizing the oral cavity that can have both synergistic and antagonistic interactions with other bacteria. Interkingdom polymicrobial associations modify fungal pathogenicity and are believed to increase microbial resistance to innate immunity. However, it is not known how these interactions alter fungal survival during phagocytic killing. We demonstrated that secreted molecules of S. gordonii and P. aeruginosa alter C. albicans survival within the phagosome of macrophages and alter fungal pathogenic phenotypes, including filamentation and microcolony formation. Moreover, we provide evidence for a dual interaction between S. gordonii and C. albicans such that S. gordonii signaling peptides can promote C. albicans commensalism by decreasing microcolony attachment while increasing invasion in epithelial cells. Our results identify bacterial diffusible factors as an attractive target to modify virulence of C. albicans in polymicrobial infections. Phagocytic cells are crucial components of the innate immune system preventing Candida albicans mucosal infections. Streptococcus gordonii and Pseudomonas aeruginosa often colonize mucosal sites, along with C. albicans, and yet interkingdom interactions that might alter the survival and escape of fungi from macrophages are not understood. Murine macrophages were coinfected with S. gordonii or P. aeruginosa, along with C. albicans to evaluate changes in fungal survival. S. gordonii increased C. albicans survival and filamentation within macrophage phagosomes, while P. aeruginosa reduced fungal survival and filamentation. Coinfection with S. gordonii resulted in greater escape of C. albicans from macrophages and increased size of fungal microcolonies formed on macrophage monolayers, while coinfection with P. aeruginosa reduced macrophage escape and produced smaller microcolonies. Microcolonies formed in the presence of P. aeruginosa cells outside macrophages also had significantly reduced size that was not found with P. aeruginosa phenazine deletion mutants. S. gordonii cells, as well as S. gordonii heat-fixed culture supernatants, increased C. albicans microcolony biomass but also resulted in microcolony detachment. A heat-resistant, trypsin-sensitive pheromone processed by S. gordonii Eep was needed for these effects. The majority of fungal microcolonies formed on human epithelial monolayers with S. gordonii supernatants developed as large floating structures with no detectable invasion of epithelium, along with reduced gene expression of C. albicansHYR1, EAP1, and HWP2 adhesins. However, a subset of C. albicans microcolonies was smaller and had greater epithelial invasiveness compared to microcolonies grown without S. gordonii. Thus, bacteria can alter the killing and escape of C. albicans from macrophages and contribute to changes in C. albicans pathogenicity. IMPORTANCECandida albicans is the predominant fungus colonizing the oral cavity that can have both synergistic and antagonistic interactions with other bacteria. Interkingdom polymicrobial associations modify fungal pathogenicity and are believed to increase microbial resistance to innate immunity. However, it is not known how these interactions alter fungal survival during phagocytic killing. We demonstrated that secreted molecules of S. gordonii and P. aeruginosa alter C. albicans survival within the phagosome of macrophages and alter fungal pathogenic phenotypes, including filamentation and microcolony formation. Moreover, we provide evidence for a dual interaction between S. gordonii and C. albicans such that S. gordonii signaling peptides can promote C. albicans commensalism by decreasing microcolony attachment while increasing invasion in epithelial cells. Our results identify bacterial diffusible factors as an attractive target to modify virulence of C. albicans in polymicrobial infections.
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Lu Y, Su C, Ray S, Yuan Y, Liu H. CO 2 Signaling through the Ptc2-Ssn3 Axis Governs Sustained Hyphal Development of Candida albicans by Reducing Ume6 Phosphorylation and Degradation. mBio 2019; 10:e02320-18. [PMID: 30647154 DOI: 10.1128/mBio.02320-18] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Candida albicans is the most common cause of invasive fungal infections in humans. Its ability to sense and adapt to changing carbon dioxide levels is crucial for its pathogenesis. Carbon dioxide promotes hyphal development. The hypha-specific transcription factor Ume6 is rapidly degraded in air, but is stable under physiological CO2 and hypoxia to sustain hyphal elongation. Here, we show that Ume6 stability is regulated by two parallel E3 ubiquitin ligases, SCFGrr1 and Ubr1, in response to CO2 and O2, respectively. To uncover the CO2 signaling pathway that regulates Ume6 stability, we performed genetic screens for mutants unable to respond to CO2 for sustained filamentation. We find that the type 2C protein phosphatase Ptc2 is specifically required for CO2-induced stabilization of Ume6 and hyphal elongation. In contrast, the cyclin-dependent kinase Ssn3 is found to be required for Ume6 phosphorylation and degradation in atmospheric CO2 Furthermore, we find that Ssn3 is dephosphorylated in 5% CO2 in a Ptc2-dependent manner, whereas deletion of PTC2 has no effect on Ssn3 phosphorylation in air. Our study uncovers the Ptc2-Ssn3 axis as a new CO2 signaling pathway that controls hyphal elongation by regulating Ume6 stability in C. albicans IMPORTANCE The capacity to sense and adapt to changing carbon dioxide levels is crucial for all organisms. In fungi, CO2 is a key determinant involved in fundamental biological processes, including growth, morphology, and virulence. In the pathogenic fungus Candida albicans, high CO2 is directly sensed by adenylyl cyclase to promote hyphal growth. However, little is known about the mechanism by which hyphal development is maintained in response to physiological levels of CO2 Here we report that a signal transduction system mediated by a phosphatase-kinase pair controls CO2-responsive Ume6 phosphorylation and stability that in turn dictate hyphal elongation. Our results unravel a new regulatory mechanism of CO2 signaling in fungi.
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Le Pioufle O, Declerck S. Reducing Water Availability Impacts the Development of the Arbuscular Mycorrhizal Fungus Rhizophagus irregularis MUCL 41833 and Its Ability to Take Up and Transport Phosphorus Under in Vitro Conditions. Front Microbiol 2018; 9:1254. [PMID: 29942294 PMCID: PMC6004939 DOI: 10.3389/fmicb.2018.01254] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Accepted: 05/24/2018] [Indexed: 12/02/2022] Open
Abstract
Climate change scenarios predict a higher variability in rainfall and an increased risk of water deficits during summers for the coming decades. For this reason, arbuscular mycorrhizal fungi (AMF) and their mitigating effects on drought stress in plants are increasingly considered in crop management. However, the impact of a decrease in water availability on the development of AMF and their ability to take up and transport inorganic phosphorus (Pi) to their hosts remain poorly explored. Here, Medicago truncatula plantlets were grown in association with Rhizophagus irregularis MUCL 41833 in bi-compartmented Petri plates. The system consisted in associating the plant and AMF in a root compartment (RC), allowing only the hyphae to extend in a root-free hyphal compartment (HC). Water availability in the HC was then lowered by increasing the concentration of polyethylene glycol-8000 (PEG-8000) from 0 to 10, 25, and 50 g L-1 (corresponding to a slight decrease in water potential of -0.024, -0.025, -0.030, and -0.056 Mpa, respectively). Hyphal growth, spore production and germination were severely impaired at the lowest water availability. The dynamics of Pi uptake by the AMF was also impacted, although total Pi uptake evaluated after 24 h stayed unchanged. The percentage of metabolically active extraradical hyphae remained above 70%. Finally, at the lowest water availability, a higher P concentration was observed in the shoots of M. truncatula. At reduced water availability, the extraradical mycelium (ERM) development was impacted, potentially limiting its capacity to explore a higher volume of soil. Pi uptake was slowed down but not prevented. The sensitivity of R. irregularis MUCL 41833 to a, even small, decrease in water availability contrasted with several studies reporting tolerance of AMF to drought. This suggests a species or strain-dependent effect and support the necessity to compare the impact of water availability on morpho-anatomy, nutrient uptake and transport capacities of other, potentially more drought-tolerant (e.g., isolated from dry environments) AMF.
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Affiliation(s)
| | - Stéphane Declerck
- Earth and Life Institute, Applied Microbiology, Mycology, Université catholique de Louvain, Louvain-la-Neuve, Belgium
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Affiliation(s)
- Anuj Kumar
- a Department of Molecular , Cellular, and Developmental Biology and Program in Cellular and Molecular Biology; University of Michigan ; Ann Arbor , MI , USA
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Yu XY, Fu F, Kong WN, Xuan QK, Wen DH, Chen XQ, He YM, He LH, Guo J, Zhou AP, Xi YH, Ni LJ, Yao YF, Wu WJ. Streptococcus agalactiae Inhibits Candida albicans Hyphal Development and Diminishes Host Vaginal Mucosal TH17 Response. Front Microbiol 2018. [PMID: 29527193 PMCID: PMC5829043 DOI: 10.3389/fmicb.2018.00198] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Streptococcus agalactiae and Candida albicans often co-colonize the female genital tract, and under certain conditions induce mucosal inflammation. The role of the interaction between the two organisms in candidal vaginitis is not known. In this study, we found that co-infection with S. agalactiae significantly attenuated the hyphal development of C. albicans, and that EFG1-Hwp1 signal pathway of C. albicans was involved in this process. In a mouse model of vulvovaginal candidiasis (VVC), the fungal burden and the levels of pro-inflammatory cytokines, IL-1β, IL-6 and TNF-α showed a increase on co-infection with S. agalactiae, while the level of TH17 T cells and IL-17 in the cervicovaginal lavage fluid were significantly decreased. Our results indicate that S. agalactiae inhibits C. albicans hyphal development by downregulating the expression of EFG1-Hwp1. The interaction between S. agalactiae and C. albicans may attenuate host vaginal mucosal TH17 immunity and contribute to mucosal colonization by C. albicans.
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Affiliation(s)
- Xiao-Yu Yu
- Department of Laboratory Medicine, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Fei Fu
- Department of Obstetrics and Gynecology, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Wen-Na Kong
- Department of Laboratory Medicine, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Qian-Kun Xuan
- Department of Laboratory Medicine, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Dong-Hua Wen
- Department of Laboratory Medicine, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Xiao-Qing Chen
- Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China
| | - Yong-Ming He
- Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China
| | - Li-Hua He
- Department of Laboratory Medicine, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Jian Guo
- Department of Laboratory Medicine, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Ai-Ping Zhou
- Department of Laboratory Medicine, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yang-Hong Xi
- Department of Laboratory Medicine, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Li-Jun Ni
- Department of Laboratory Medicine, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yu-Feng Yao
- Department of Laboratory Medicine, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Wen-Juan Wu
- Department of Laboratory Medicine, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China
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Mello TP, Aor AC, Gonçalves DS, Seabra SH, Branquinha MH, Santos ALS. Assessment of biofilm formation by Scedosporium apiospermum, S. aurantiacum, S. minutisporum and Lomentospora prolificans. Biofouling 2016; 32:737-749. [PMID: 27309801 DOI: 10.1080/08927014.2016.1192610] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 05/12/2016] [Indexed: 06/06/2023]
Abstract
Reported herein is the ability of Scedosporium apiospermum, S. aurantiacum, S. minutisporum and Lomentospora prolificans conidia to adhere, differentiate into hyphae and form biofilms on both polystyrene and lung epithelial cells. To different degrees, all of the fungi adhered to polystyrene after 4 h, with a predominance of those with germinated conidia. Prolonged fungi-polystyrene contact resulted in the formation of a monolayer of intertwined mycelia, which was identified as a typical biofilm structure due to the presence of a viable mycelial biomass, extracellular matrix and enhanced antifungal resistance. Ultrastructural details were revealed by SEM and CLSM, showing the dense compaction of the mycelial biomass and the presence of channels within the organized biofilm. A similar biofilm structure was observed following the co-culture of each fungus with A549 cells, revealing a mycelial trap covering all of the lung epithelial monolayer. Collectively, these results highlight the potential for biofilm formation by these clinically relevant fungal pathogens.
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Affiliation(s)
- Thaís P Mello
- a Laboratório de Investigação de Peptidases, Departamento de Microbiologia Geral, Instituto de Microbiologia Paulo de Góes , Universidade Federal do Rio de Janeiro , Rio de Janeiro , Brazil
| | - Ana Carolina Aor
- a Laboratório de Investigação de Peptidases, Departamento de Microbiologia Geral, Instituto de Microbiologia Paulo de Góes , Universidade Federal do Rio de Janeiro , Rio de Janeiro , Brazil
| | - Diego S Gonçalves
- a Laboratório de Investigação de Peptidases, Departamento de Microbiologia Geral, Instituto de Microbiologia Paulo de Góes , Universidade Federal do Rio de Janeiro , Rio de Janeiro , Brazil
- b Programa de Pós-Graduação em Bioquímica, Instituto de Química , Universidade Federal do Rio de Janeiro , Rio de Janeiro , Brazil
| | - Sergio H Seabra
- c Laboratório de Tecnologia em Cultura de Células , Centro Universitário Estadual da Zona Oeste (UEZO) , Rio de Janeiro , Brazil
| | - Marta H Branquinha
- a Laboratório de Investigação de Peptidases, Departamento de Microbiologia Geral, Instituto de Microbiologia Paulo de Góes , Universidade Federal do Rio de Janeiro , Rio de Janeiro , Brazil
| | - André L S Santos
- a Laboratório de Investigação de Peptidases, Departamento de Microbiologia Geral, Instituto de Microbiologia Paulo de Góes , Universidade Federal do Rio de Janeiro , Rio de Janeiro , Brazil
- b Programa de Pós-Graduação em Bioquímica, Instituto de Química , Universidade Federal do Rio de Janeiro , Rio de Janeiro , Brazil
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