The Fungal Mycobiota: Small Numbers, Large Impacts

The gut mycobiome signatures in long-lived populations

Long-lived individuals have been extensively studied as a model to investigate the role of the gut microbiota in aging, but their gut fungi remain almost unexplored. Here, we recruited a community-dwelling cohort of 251 participants (24-108 years, including 47 centenarians) from Guangxi in China to characterize the gut mycobiome signatures. We found gut mycobiome markedly varied during aging and determined aging as a predominant factor driving these variations. For long-lived individuals, core taxa, including Penicillium and Aspergillus, were maintained and Candida enterotype was enriched when compared with old counterparts. Individuals with this enterotype were more likely to possess Bacteroides enterotype enriched in young and centenarians. Moreover, the drivers from Candida enterotype were positively linked with the bacteria components dominated in Bacteroides enterotype. We also identified potentially beneficial yeasts-enriched features to differentiate long-lived individuals from others. Our findings suggest that the gut mycobiome develops with aging, and long-lived individuals possess unique fungal signatures.

From ASCA breakthrough in Crohn's disease and Candida albicans research to thirty years of investigations about their meaning in human health

Anti-Saccharomyces cerevisiae antibodies (ASCA) are human antibodies that can be detected using an enzyme-linked immunosorbent assay involving a mannose polymer (mannan) extracted from the cell wall of the yeast S. cerevisiae. The ASCA test was developed in 1993 with the aim of differentiating the serological response in two forms of inflammatory bowel disease (IBD), Crohn's disease and ulcerative colitis. The test, which is based on the detection of anti-oligomannosidic antibodies, has been extensively performed worldwide and there have been hundreds of publications on ASCA. The earlier studies concerned the initial diagnostic indications of ASCA and investigations then extended to many human diseases, generally in association with studies on intestinal microorganisms and the interaction of the micro-mycobiome with the immune system. The more information accumulates, the more the mystery of the meaning of ASCA deepens. Many fundamental questions remain unanswered. These questions concern the heterogeneity of ASCA, the mechanisms of their generation and persistence, the existence of self-antigens, and the relationship between ASCA and inflammation and autoimmunity. This review aims to discuss the gray areas concerning the origin of ASCA from an analysis of the literature. Structured around glycobiology and the mannosylated antigens of S. cerevisiae and Candida albicans, this review will address these questions and will try to clarify some lines of thought. The importance of the questions relating to the pathophysiological significance of ASCA goes far beyond IBD, even though these diseases remain the preferred models for their understanding.

Intestinal bacteria-a powerful weapon for fungal infections treatment

The morbidity and mortality of invasive fungal infections are rising gradually. In recent years, fungi have quietly evolved stronger defense capabilities and increased resistance to antibiotics, posing huge challenges to maintaining physical health. Therefore, developing new drugs and strategies to combat these invasive fungi is crucial. There are a large number of microorganisms in the intestinal tract of mammals, collectively referred to as intestinal microbiota. At the same time, these native microorganisms co-evolve with their hosts in symbiotic relationship. Recent researches have shown that some probiotics and intestinal symbiotic bacteria can inhibit the invasion and colonization of fungi. In this paper, we review the mechanism of some intestinal bacteria affecting the growth and invasion of fungi by targeting the virulence factors, quorum sensing system, secreting active metabolites or regulating the host anti-fungal immune response, so as to provide new strategies for resisting invasive fungal infection.

What happens to gut microorganisms and potential repair mechanisms when meet heavy metal(loid)s

Heavy metal (loid) pollution is a significant threat to human health, as the intake of heavy metal (loid)s can cause disturbances in intestinal microbial ecology and metabolic disorders, leading to intestinal and systemic diseases. Therefore, it is important to understand the effects of heavy metal (loid)s on intestinal microorganisms and the necessary approaches to restore them after damage. This review provides a summary of the effects of common toxic elements, such as lead (Pb), cadmium (Cd), chromium (Cr), and metalloid arsenic (As), on the microbial community and structure, metabolic pathways and metabolites, and intestinal morphology and structure. The effects of heavy metal (loid)s on metabolism are focused on energy, nitrogen, and short-chain fatty acid metabolism. We also discussed the main solutions for recovery of intestinal microorganisms from the effects of heavy metal (loid)s, namely the supplementation of probiotics, recombinant bacteria with metal resistance, and the non-toxic transformation of heavy metal (loid) ions by their own intestinal flora. This article provides insight into the toxic effects of heavy metals and As on gut microorganisms and hosts and provides additional therapeutic options to mitigate the damage caused by these toxic elements.

The mitochondrial complex I proteins of Candida albicans moderate phagocytosis and the production of pro-inflammatory cytokines in murine macrophages and dendritic cells

Loss of respiratory functions impairs Candida albicans colonization of host tissues and virulence in a murine model of candidiasis. Furthermore, it is known that respiratory inhibitors decrease mannan synthesis and glucan exposure and thereby promotes phagocytosis. To understand the impact of respiratory proteins of C. albicans on host innate immunity, we characterized cell wall defects in three mitochondrial complex I (CI) null mutants (nuo1Δ, nuo2Δ and ndh51Δ) and in one CI regulator mutant (goa1Δ), and we studied the corresponding effects of these mutants on phagocytosis, neutrophil killing and cytokine production by dendritic cells (DCs). We find that reductions of phosphopeptidomannan (PPM) in goa1Δ, nuo1Δ and phospholipomannan (PLM) in nuo2Δ lead to reductions of IL-2, IL-4, and IL-10 but increase of TNF-α in infected DCs. While PPM loss is a consequence of a reduced phospho-Cek1/2 MAPK that failed to promote phagocytosis and IL-22 production in goa1Δ and nuo1Δ, a 30% glucan reduction and a defective Mek1 MAPK response in ndh51Δ lead to only minor changes in phagocytosis and cytokine production. Glucan exposure and PLM abundance seem to remain sufficient to opsonize neutrophil killing perhaps via humoral immunity. The diversity of immune phenotypes in these mutants possessing divergent cell wall defects is further supported by their transcriptional profiles in each infected murine macrophage scenario. Since metabolic processes, oxidative stress-induced senescence, and apoptosis are differently affected in these scenarios, we speculate that during the early stages of infection, host immune cells coordinate their bioactivities based upon a mixture of signals generated during host-fungi interactions.

Microbiota and COVID-19: Long-term and complex influencing factors

The coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). According to the World Health Organization statistics, more than 500 million individuals have been infected and more than 6 million deaths have resulted worldwide. Although COVID-19 mainly affects the respiratory system, considerable evidence shows that the digestive, cardiovascular, nervous, and reproductive systems can all be involved. Angiotensin-converting enzyme 2 (AEC2), the target of SARS-CoV-2 invasion of the host is mainly distributed in the respiratory and gastrointestinal tract. Studies found that microbiota contributes to the onset and progression of many diseases, including COVID-19. Here, we firstly conclude the characterization of respiratory, gut, and oral microbial dysbiosis, including bacteria, fungi, and viruses. Then we explore the potential mechanisms of microbial involvement in COVID-19. Microbial dysbiosis could influence COVID-19 by complex interactions with SARS-CoV-2 and host immunity. Moreover, microbiota may have an impact on COVID-19 through their metabolites or modulation of ACE2 expression. Subsequently, we generalize the potential of microbiota as diagnostic markers for COVID-19 patients and its possible association with post-acute COVID-19 syndrome (PACS) and relapse after recovery. Finally, we proposed directed microbiota-targeted treatments from the perspective of gut microecology such as probiotics and prebiotics, fecal transplantation and antibiotics, and other interventions such as traditional Chinese medicine, COVID-19 vaccines, and ACE2-based treatments.

Customized materials-assisted microorganisms in tumor therapeutics

Microorganisms have been extensively applied as active biotherapeutic agents or drug delivery vehicles for antitumor treatment because of their unparalleled bio-functionalities. Taking advantage of the living attributes of microorganisms, a new avenue has been opened in anticancer research. The integration of customized functional materials with living microorganisms has demonstrated unprecedented potential in solving existing questions and even conferring microorganisms with updated antitumor abilities and has also provided an innovative train of thought for enhancing the efficacy of microorganism-based tumor therapy. In this review, we have summarized the emerging development of customized materials-assisted microorganisms (MAMO) (including bacteria, viruses, fungi, microalgae, as well as their components) in tumor therapeutics with an emphasis on the rational utilization of chosen microorganisms and tailored materials, the ingenious design of biohybrid systems, and the efficacious antitumor mechanisms. The future perspectives and challenges in this field are also discussed.

Candida albicans triggers qualitative and temporal responses in gut bacteria

Interactions between commensal intestinal bacteria and fungi are collectively beneficial in maintaining the balance of the gut microflora and preventing gastrointestinal diseases. However, the contributions of specific bacterial species in response to fungal dysbiosis in the gut remain poorly defined. Here, to understand the dynamic changes, we established acute a challenge with Candida albicans in mice treated without antibiotics and analyzed the changes in the diversity of bacteria during the imbalance in intestinal C. albicans with high-throughput amplicon sequencing. Our results showed significant increases in species diversity after the first day of fungal challenge and the restoration of balance among the gut microflora on the third day of challenge. To explore the interactions between the intestinal bacteria and C. albicans, the antifungal activities of bacteria isolated from the mouse feces were also determined. Nineteen aerobic bacteria with antifungal activity were identified with whole 16S rRNA gene sequencing. These bacteria were isolated on the first day of challenge more than on the third day. These results suggested that the commensal intestinal bacteria may protect the host against fungal dysbiosis in the gut by altering their own species diversity. The interaction between bacteria and fungi in the gut may be the key to maintaining the dynamic balance of microorganisms in the context of environmental changes.

Influence of Fluconazole Administration on Gut Microbiome, Intestinal Barrier, and Immune Response in Mice

Antibiotics that can treat or prevent infectious diseases play an important role in medical therapy. However, the use of antibiotics has potentially negative effects on the health of the host. For example, antibiotics use may affect the host's immune system by altering the gut microbiota. Therefore, the aim of the study was to investigate the influence of antifungal (fluconazole) treatment on the gut microbiota and immune system of mice. Results showed that the gut microbial composition of mice receiving fluconazole treatment was significantly changed after the trial. Fluconazole did not affect the relative abundance of bacteria but significantly reduced the diversity of bacterial flora. In the bacteriome, Firmicutes and Proteobacteria significantly increased, while Bacteroidetes, Deferribacteres, Patescibacteria, and Tenericutes showed a remarkable reduction in the fluconazole-treated group compared with the control group. In the mycobiome, the relative abundance of Ascomycota was significantly decreased and Mucoromycota was significantly increased in the intestine of mice treated with fluconazole compared to the control group. Reverse transcription-quantitative PCR (RT-qPCR) results showed that the relative gene expression of ZO-1, occludin, MyD88, interleukin-1β (IL-1β), and IL-6 was decreased in the fluconazole-treated group compared to the control. Serum levels of IL-2, LZM, and IgM were significantly increased, while the IgG level was considerably downregulated in the fluconazole-treated compared to the control group. These results suggest that the administration of fluconazole can influence the gut microbiota and that a healthy gut microbiome is important for the regulation of the host immune responses.

Intestinal mycobiota in health and diseases: from a disrupted equilibrium to clinical opportunities

Bacteria, viruses, protozoa, and fungi establish a complex ecosystem in the gut. Like other microbiota, gut mycobiota plays an indispensable role in modulating intestinal physiology. Notably, the most striking characteristics of intestinal fungi are their extraintestinal functions. Here, we provide a comprehensive review of the importance of gut fungi in the regulation of intestinal, pulmonary, hepatic, renal, pancreatic, and brain functions, and we present possible opportunities for the application of gut mycobiota to alleviate/treat human diseases. Video Abstract.

Tonsil Mycobiome in PFAPA (Periodic Fever, Aphthous Stomatitis, Pharyngitis, Adenitis) Syndrome: A Case-Control Study

Periodic fever, aphthous stomatitis, pharyngitis and adenitis syndrome (PFAPA) is the most common periodic fever syndrome in children with unknown etiology, effectively treated with tonsillectomy. Earlier we have shown that tonsil microbiome is different in patients with PFAPA as compared to that in controls. Recently, fungal microbiome, mycobiome, has been linked to the pathogenesis of inflammatory diseases. We now investigated the role of mycobiome of tonsils in PFAPA. Random forest classification, a machine learning approach, was used for the analysis of mycobiome data. We examined tonsils from 30 children with PFAPA and 22 control children undergoing tonsillectomy for non-infectious reasons. We identified 103 amplicon sequence variants, mainly from two fungal phyla, Ascomycota and Basidiomycota. The mean relative abundance of Candida albicans in the tonsil mycobiome was 11% (95% CI: 19 to 27%) in cases and 3.4 % (95% CI: -0.8% to 8%) in controls, p =0.104. Mycobiome data showed no statistical difference in differentiating between PFAPA cases and controls compared to a random chance classifier (area under the curve (AUC) = 0.47, SD = 0.05, p = 0.809). In conclusion, in this controlled study, tonsillar mycobiome in children with PFAPA syndrome did not differ from that of the controls.

The Oral Microbiome in Pediatric IBD: A Source of Pathobionts or Biomarkers?

The oral cavity is continuous with the gastrointestinal tract and in children, oral health may be closely linked with the overall health of the GI tract. In the case of pediatric Crohn's disease (CD), oral manifestations are an important clinical indicator of intestinal disease. Recent studies of the microbiome in IBD suggest that translocation of oral microbes to the gut may be a common feature of the microbial dysbiosis which is a signature of both CD and ulcerative colitis (UC). Murine studies suggest that translocation of oral bacteria and yeasts to the lower GI tract may trigger inflammation in susceptible hosts, providing a mechanistic link to the development of IBD. Conversely, some studies have shown that dysbiosis of the oral microbiome may occur, possibly as a result of inflammatory responses and could represent a useful source of biomarkers of GI health. This review summarizes our current knowledge of the oral microbiome in IBD and presents current hypotheses on the potential role of this community in the pathogenesis of these diseases.

The mycobiome in murine intestine is more perturbed by food arsenic exposure than in excreted feces

Arsenic is a global pollutant that can accumulate in rice and has been confirmed to disturb the gut microbiome. By contrast, the influence on the gut mycobiome is seldom concerned because fungi comprise a numerically small proportion of the whole gut microcommunity. To expand the detection of the mycobiome in different gut sections of mammals and investigate the influence of food arsenic on the gut mycobiome in the digestive tract, we treated mice with feeds containing different compositions of arsenic species (7.3% sodium arsenate, 72.7% sodium arsenite, 1.0% sodium monomethylarsonate, and 19.0% sodium dimethylarsinate) in rice at a total arsenic dose of 30 mg/kg. After 60 days of exposure, the feces of four different sites, the ileum, cecum, colon, and excreted feces, were collected and analyzed by internal transcribed spacer gene sequencing. Among the samples, the major fungal phyla were Ascomycota, Basidiomycota, and Zygomycota; the top 10 fungal genera were Aspergillus, Verticillium, Penicillium, Cladosporium, Alternaria, Fusarium, Ophiocordyceps, Trametes, Mucor, and Nigrospora. In control mice, along the murine digestive tract, the mycobial richness and composition were significantly changed; Aspergillus and Penicillium possessed the higher ability to be stabilized in the murine gut, and larger proportions of positive correlations were observed among the major fungi. After arsenic exposure, the fungal composition was more disturbed in the intestinal tract than in feces. Along the digestive tract, arsenic can trigger larger mycobial variations, and the sensitivities of major fungi to arsenic were changed. Thus, the murine intestinal spatial mycobiota are more perturbed than excreted fecal mycobiota after food arsenic exposure. Feces are insufficient to be selected as a representative of the gut mycobiota in arsenic exposure studies.

Gut mycobiomes are altered in people with type 2 Diabetes Mellitus and Diabetic Retinopathy

Studies have documented dysbiosis in the gut mycobiome in people with Type 2 diabetes mellitus (T2DM). However, it is not known whether dysbiosis in the gut mycobiome of T2DM patients would be reflected in people with diabetic retinopathy (DR) and if so, is the observed mycobiome dysbiosis similar in people with T2DM and DR. Gut mycobiomes were generated from healthy controls (HC), people with T2DM and people with DR through Illumina sequencing of ITS2 region. Data were analysed using QIIME and R software. Dysbiotic changes were observed in people with T2DM and DR compared to HC at the phyla and genera level. Mycobiomes of HC, T2DM and DR could be discriminated by heat map analysis, Beta diversity analysis and LEfSE analysis. Spearman correlation of fungal genera indicated more negative correlation in HC compared to T2DM and DR mycobiomes. This study demonstrates dysbiosis in the gut mycobiomes in people with T2DM and DR compared to HC. These differences were significant both at the phyla and genera level between people with T2DM and DR as well. Such studies on mycobiomes may provide new insights and directions to identification of specific fungi associated with T2DM and DR and help developing novel therapies for Diabetes Mellitus and DR.

The Fungal Microbiome and Asthma

Asthma is a group of inflammatory conditions that compromises the airways of a continuously increasing number of people around the globe. Its complex etiology comprises both genetic and environmental aspects, with the intestinal and lung microbiomes emerging as newly implicated factors that can drive and aggravate asthma. Longitudinal infant cohort studies combined with mechanistic studies in animal models have identified microbial signatures causally associated with subsequent asthma risk. The recent inclusion of fungi in human microbiome surveys has revealed that microbiome signatures associated with asthma risk are not limited to bacteria, and that fungi are also implicated in asthma development in susceptible individuals. In this review, we examine the unique properties of human-associated and environmental fungi, which confer them the ability to influence immune development and allergic responses. The important contribution of fungi to asthma development and exacerbations prompts for their inclusion in current and future asthma studies in humans and animal models.

Interactions of microorganisms with host mucins: a focus on Candida albicans

Mucus is an important host innate defense factor that lines most epithelial cell layers of the body and provides crucial physical and biological protection against pathogenic microorganisms. Mucins are the main glycoproteins of mucus that are responsible for interacting with microorganisms and are critical for the antimicrobial properties of mucus. The mechanisms by which microorganisms interact with mucins are poorly understood, especially in terms of fungi, and these interactions are continually evolving. Work in bacterial pathogens has shown that mucins inhibit bacterial virulence traits, including quorum sensing, toxin secretion and biofilm formation. Among the fungal clade, the common opportunistic human fungal pathogen and commensal Candida albicans engages in constant battle with the host innate immune system. This battle creates strong selective pressures for C. albicans to evolve in response to the host. Recent work in C. albicans found that mucins inhibit specific virulence traits, such as surface adherence, filamentation, biofilm formation and the production of secreted proteases. Here we review the current knowledge of microbial interactions with mucins, with a special emphasis on the interactions between C. albicans and mucins.

Interactions between invasive fungi and symbiotic bacteria

Infection rates and mortality associated with the invasive fungi Candida, Aspergillus, and Cryptococcus are increasing rapidly in prevalence. Meanwhile, screening pressure brought about by traditional antifungal drugs has induced an increase in drug resistance of invasive fungi, which creates a great challenge for the preservation of physical health. Development of new drugs and novel strategies are therefore important to meet these growing challenges. Recent studies have confirmed that the dynamic balance of microorganisms in the body is correlated with the occurrence of infectious diseases. This discovery of interactions between bacteria and fungi provides innovative insight for the treatment of invasive fungal infections. However, different invasive fungi and symbiotic bacteria interact with each other through various ways and targets, leading to different effects on their growth, morphology, and virulence. And the mechanism and implication of these interactions remains largely unknown. The present review aims to summarize the research progress into the interaction between invasive fungi and symbiotic bacteria with a focus on the anti-fungal mechanisms of symbiotic bacteria, providing a new strategy against drug-resistant fungal infections.

The mycobiota of the human body: a spark can start a prairie fire

Mycobiota are inseparable from human health, shaking up the unique position held by bacteria among microorganisms. What is surprising is that this seemingly small species can trigger huge changes in the human body. Dysbiosis and invasion of mycobiota are confirmed to cause disease in different parts of the body. Meanwhile, our body also produces corresponding immune changes upon mycobiota infection. Several recent studies have made a connection between intestinal mycobiota and the human immune system. In this review, we focus on questions related to mycobiota, starting with an introduction of select species, then we summarize the typical diseases caused by mycobiota in different parts of the human body. Moreover, we constructed a framework for the human anti-fungal immune system based on genetics and immunology. Finally, the progression of fungal detection methods is also reviewed.

The Fungal Microbiome and Asthma

Asthma is a group of inflammatory conditions that compromises the airways of a continuously increasing number of people around the globe. Its complex etiology comprises both genetic and environmental aspects, with the intestinal and lung microbiomes emerging as newly implicated factors that can drive and aggravate asthma. Longitudinal infant cohort studies combined with mechanistic studies in animal models have identified microbial signatures causally associated with subsequent asthma risk. The recent inclusion of fungi in human microbiome surveys has revealed that microbiome signatures associated with asthma risk are not limited to bacteria, and that fungi are also implicated in asthma development in susceptible individuals. In this review, we examine the unique properties of human-associated and environmental fungi, which confer them the ability to influence immune development and allergic responses. The important contribution of fungi to asthma development and exacerbations prompts for their inclusion in current and future asthma studies in humans and animal models.

[Human mycobiome and diseases]

The proportion of mycobiome is less than 1% of human microbiome. However, fungal community plays a key role in human health and diseases. With high-throughput sequencing applications, the structure and composition of mycobiome in the mouth, lung, gut, vagina, and skin have been analyzed, and the role of microbiome in diseases has been investigated. Mycobiome also influences the composition of bacteriome and includes key species that maintain the structure and function of microbial communities. Fungi also influence host immune responses. In this review, we summarized the mycobiome com-position at various sites and different diseases and the interactions between fungi-bacteria and fungi-host.

Fungi-Induced Upper and Lower Respiratory Tract Allergic Diseases: One Entity

Introduction:Aspergillus can cause different allergic diseases including allergic bronchopulmonary aspergillosis (ABPA) and allergic fungal rhinosinusitis (AFRS). ABPA is allergic pulmonary disease against Aspergillus antigens. AFRS is a type of chronic rhinosinusitis (CRS) presented as hypersensitivity reactions to the fungal presence in sinuses. The aim of the present study was to clarify if ABPA and AFRS could be considered as a common disease entity.

Methodology: The prospective cohort study included 75 patients with ABPA. Patients were divided into two groups and compared with each other: (i) patients with CT confirmation of rhinosinusitis and presence of fungi in sinuses (ABPA+AFRS group) and (ii) patients without CT or without mycological evidence of AFRS (ABPA group).

Results: Findings of this study were: (i) AFRS was confirmed in 80% of patients with ABPA; (ii) all ABPA+AFRS patients had allergic mucin while fungal hyphae were present in 60% sinonasal aspirate; (iii) ABPA+AFRS patients had more often complicated CRS with (nasal polyps) NP (p < 0.001) and more severe forms of CRS; (iv) culture of sinonasal aspirate revealed fungal presence in 97% patients with ABPA+AFRS; (v) patients with ABPA+AFRS had more common positive skin prick test (SPT) for A. fumigatus (p = 0.037), while patients without AFRS had more common positive SPT for Alternaria alternata and Penicillium notatum (p = 0.04 and p = 0.03, respectively); (vi) 67% of ABPA patients had Aspergillus induced AFRS; (vii) larger number of fungi was isolated from the air-samples obtained from homes of patients with ABPA+AFRS than from the homes of patients without AFRS, while the most predominant species were A. fumigatus and A. niger isolated from almost 50% of the air-samples.

Conclusion: The pathogenesis of ABPA and AFRS is similar, and AFRS can be considered as the upper airway counterpart of ABPA. Fungi-induced upper and lower respiratory tract allergic diseases present common entity. Next studies should clarify the mechanism by which fungi turn from “normal flora” into trigger of immunological reactions, resulting in ABPA or AFRS as well as to find new approaches for its' diagnosis and treatment.

Fungal Diversity of Human Gut Microbiota Among Eutrophic, Overweight, and Obese Individuals Based on Aerobic Culture-Dependent Approach

Fungi have a complex role in the intestinal tract, influencing health and disease, with dysbiosis contributing to obesity. Our objectives were to investigate fungal diversity in human gut microbiota among eutrophic, overweight, and obese. Epidemiological and nutritional information were collected from adult individuals, as well as stool samples processed for selective fungi isolation and identification by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (yeasts) or microculture (filamentous fungi). Further 18S rDNA sequencing was performed to confirm identification. The mean count of fungi was 241 CFU/g of feces. Differences in the population level of the filamentous fungi were observed within eutrophic and obese groups. Overall, 34 genera were identified. The predominant phylum was Ascomycota with 20 different genera, followed by Basidiomycota and Zygomycota. As for Ascomycota, the most prevalent species were Paecilomyces sp., Penicillium sp., Candida sp., Aspergillus sp., Fonsecaea sp., and Geotrichum sp. (76.39, 65.28, 59.72, 58.33, 12.50, and 9.72%, respectively). As for Basidiomycota, Trichosporon sp. and Rhodotorula sp. were the most prevalent (30.56 and 15.28%, respectively), and for Zygomycota, Rhizopus sp. and Mucor sp. were the most numerous (15.28 and 9.72%, respectively). As expected there is a mycobiota shift towards obesity, with slightly higher diversity associated to eutrophic individuals. This mycobiota shift seems also to be related to the nutritional behavior of the individuals, as observed that the macronutrients intake may be positively related to the different fungi occurrences. Other studies are needed to better understand relationships between mycobiota and obesity, which could be used in future obesity treatments.

Fungal Microbiota in Chronic Airway Inflammatory Disease and Emerging Relationships with the Host Immune Response

The respiratory tract is a complex system that is inhabited by niche-specific communities of microbes including bacteria, fungi, and viruses. These complex microbial assemblages are in constant contact with the mucosal immune system and play a critical role in airway health and immune homeostasis. Changes in the composition and diversity of airway microbiota are frequently observed in patients with chronic inflammatory diseases including chronic rhinosinusitis (CRS), cystic fibrosis, allergy, and asthma. While the bacterial microbiome of the upper and lower airways has been the focus of many recent studies, the contribution of fungal microbiota to inflammation is an emerging research interest. Within the context of allergic airway disease, fungal products are important allergens and fungi are potent inducers of inflammation. In addition, murine models have provided experimental evidence that fungal microbiota in peripheral organs, notably the gastrointestinal (GI) tract, influence pulmonary health. In this review, we explore the role of the respiratory and GI microbial communities in chronic airway inflammatory disease development with a specific focus on fungal microbiome interactions with the airway immune system and fungal-bacterial interactions that likely contribute to inflammatory disease. These findings are discussed in the context of clinical and immunological features of fungal-mediated disease in CRS, allergy, and asthmatic patients. While this field is still nascent, emerging evidence suggests that dysbiotic fungal and bacterial microbiota interact to drive or exacerbate chronic airway inflammatory disease.

Forgotten fungi-the gut mycobiome in human health and disease

The human body is home to a complex and diverse microbial ecosystem that plays a central role in host health. This includes a diversity of fungal species that is collectively referred to as our 'mycobiome'. Although research into the mycobiome is still in its infancy, its potential role in human disease is increasingly recognised. Here we review the existing literature available on the human mycobiota with an emphasis on the gut mycobiome, including how fungi interact with the human host and other microbes. In doing so, we provide a comprehensive critique of the methodologies available to research the human mycobiota as well as highlighting the latest research findings from mycological surveys of different groups of interest including infants, obese and inflammatory bowel disease cohorts. This in turn provides new insights and directions for future studies in this burgeoning research area.

The yeast form of the fungus Candida albicans promotes persistence in the gut of gnotobiotic mice

Many microorganisms that cause systemic, life-threatening infections in humans reside as harmless commensals in our digestive tract. Yet little is known about the biology of these microbes in the gut. Here, we visualize the interface between the human commensal and pathogenic fungus Candida albicans and the intestine of mice, a surrogate host. Because the indigenous mouse microbiota restricts C. albicans settlement, we compared the patterns of colonization in the gut of germ free and antibiotic-treated conventionally raised mice. In contrast to the heterogeneous morphologies found in the latter, we establish that in germ free animals the fungus almost uniformly adopts the yeast cell form, a proxy of its commensal state. By screening a collection of C. albicans transcription regulator deletion mutants in gnotobiotic mice, we identify several genes previously unknown to contribute to in vivo fitness. We investigate three of these regulators—ZCF8, ZFU2 and TRY4—and show that indeed they favor the yeast form over other morphologies. Consistent with this finding, we demonstrate that genetically inducing non-yeast cell morphologies is detrimental to the fitness of C. albicans in the gut. Furthermore, the identified regulators promote adherence of the fungus to a surface covered with mucin and to mucus-producing intestinal epithelial cells. In agreement with this result, histology sections indicate that C. albicans dwells in the murine gut in close proximity to the mucus layer. Thus, our findings reveal a set of regulators that endows C. albicans with the ability to endure in the intestine through multiple mechanisms.

The very same microbes that cause life-threatening human diseases are often harmless inhabitants on our mucosal surfaces. Yet the hallmarks of this so-called ‘commensal’ state remain underexplored. In this report we investigate the case of Candida albicans, the most prominent fungal species living in the human intestine but also a common cause of deep-seated, fatal infections. Mice carrying their own natural intact flora are not readily colonized by C. albicans implying a fundamental incompatibility between the indigenous mouse microbiota and this fungus. We explore the patterns of colonization of C. albicans in mice completely devoid of other microbes. We show that the fungus adopts its normal commensal morphology in these animals indicating that this experimental system is a suitable proxy to clearly dissect its commensal lifestyle in vivo. Gaining insights into the mechanisms that sustain the commensal features of C. albicans and other microbes is key to understand—and be able to prevent—what goes awry when these microorganisms invade other tissues and cause disease.