Fungal contaminants in drinking water – a topic of future concern?

Fresh water is, depending on geological features of the area, derived to the public either from groundwater or surface water. Production of clean drinking water in a modern society with increasing population and urbanisation often requires the use of different physico-chemical methods. Finally, water quality is controlled based on the parameters listed in Drinking Water Directive (98/83/CE). Fungi are not listed in the current directive and therefore not specifically monitored. However, their presence in fresh water is well documented-in the last 30 years scientists from 19 European countries isolated more than 400 different fungal species from surface, ground-and tap water intended for human consumption. While water cleaning procedures remove 8-90% of fungal propagules, the remaining ones form together with bacteria biofilms inside tap water systems, later affecting the taste and odor of water. Several water-related fungal species were recognised as opportunistic or emerging pathogens; among these fungi from the genera Aspergillus, Candida, Exophiala, Fusarium, Penicillium and Stachybotrys require special attention. Presence of opportunistic fungi in drinking water can pose a health risk to consumers due to daily contact with water via several exposure points, such as drinking, showering and use of household appliances operating with water. Case reports listing fungi as causative agents of allergies, opportunistic infections and intoxications are growing each year-12 million people are at risk of invasive fungal mycoses, additional 12 million have allergic fungal sinusitis, 4.8 million patients suffer from allergic bronchopulmonary aspergillosis, and 6 million have fungal eye infections. A billion of people around the world suffer from skin, nail, and hair infections. With increasing transitory and serious immune alterations among patients also a need for monitoring of fungi increases, not only in drinking water, but also as a parametric value for biofilm formation on materials in contact with drinking water.info:eu-repo/semantics/publishedVersio

High Incidence of an Emerging Opportunistic Pathogen <em>Candida parapsilosis</em> in Water-Related Domestic Environments

Candidiasis is one of the common fungal opportunistic infections, usually associated with diverse Candida species. Candida albicans, C. glabrata complex, C. parapsilosis complex, C. tropicalis and C. auris are often identified in affected patients. Candida parapsilosis sensu stricto is an emerging cause of hospital-acquired Candida infections, predominantly in Southern Europe, South America and Asia. Home environment is a less known source of infection despite frequent isolation of C. parapsilosis from kitchen surfaces and household appliances such as dishwashers, washing machines and refrigerators. C. parapsilosis is one of the first colonisers of novel dishwashers and a member of stable fungal communities on rubber seals worldwide in concentrations up to 102 CFU/cm2. It colonises also drawers for detergents in washing machines and drainage channels in refrigerators. Tap water and groundwater act as vector for entrance of C. parapsilosis in the indoor environments. Within C. parapsilosis, four clinically relevant phenotypes can be distinguished. Experimental data on the prevalence of C. parapsilosis isolates phenotypes, obtained from indoor environments, will be presented. Smooth phenotype prevails in dishwashers and washing machines, while crepe and crater dominate in water. In conclusion, the ability to colonise diverse environments and accordingly switch phenotypes defines C. parapsilosis as a versatile, domestic environment-related opportunistic pathogen

The MAP kinase HwHog1 from the halophilic black yeast Hortaea werneckii: coping with stresses in solar salterns

BACKGROUND: Hortaea werneckii is one of the most salt-tolerant species among microorganisms. It has been isolated from hypersaline waters of salterns as one of the predominant species of a group of halophilic and halotolerant melanized yeast-like fungi, arbitrarily named as "black yeasts". It has previously been shown that H. werneckii has distinct mechanisms of adaptation to high salinity environments that are not seen in salt-sensitive and only moderately salt-tolerant fungi. In H. werneckii, the HOG pathway is important for sensing the changes in environmental osmolarity, as demonstrated by identification of three main pathway components: the mitogen-activated protein kinase (MAPK) HwHog1, the MAPK kinase HwPbs2, and the putative histidine kinase osmosensor HwHhk7. RESULTS: In this study, we show that the expression of HwHOG1 in salt-adapted cells depends on the environmental salinity and that HwHOG1 transcription responds rapidly but reciprocally to the acute hyper-saline or hypo-saline stress. Molecular modelling of HwHog1 reveals an overall structural homology with other MAPKs. HwHog1 complements the function of ScHog1 in the Saccharomyces cerevisiae multistress response. We also show that hyper-osmolar, oxidative and high-temperature stresses activate the HwHog1 kinase, although under high-temperature stress the signal is not transmitted via the MAPK kinase Pbs2. Identification of HOG1-like genes from other halotolerant fungi isolated from solar salterns demonstrates a high degree of similarity and excellent phylogenetic clustering with orthologues of fungal origin. CONCLUSION: The HOG signalling pathway has an important role in sensing and responding to hyper-osmolar, oxidative and high-temperature stresses in the halophilic fungi H. werneckii. These findings are an important advance in our understanding of the HOG pathway response to stress in H. werneckii, a proposed model organism for studying the salt tolerance of halophilic and halotolerant eukaryotes

Low Water Activity Induces the Production of Bioactive Metabolites in Halophilic and Halotolerant Fungi

The aim of the present study was to investigate indigenous fungal communities isolated from extreme environments (hypersaline waters of solar salterns and subglacial ice), for the production of metabolic compounds with selected biological activities: hemolysis, antibacterial, and acetylcholinesterase inhibition. In their natural habitats, the selected fungi are exposed to environmental extremes, and therefore the production of bioactive metabolites was tested under both standard growth conditions for mesophilic microorganisms, and at high NaCl and sugar concentrations and low growth temperatures. The results indicate that selected halotolerant and halophilic species synthesize specific bioactive metabolites under conditions that represent stress for non-adapted species. Furthermore, adaptation at the level of the chemical nature of the solute lowering the water activity of the medium was observed. Increased salt concentrations resulted in higher hemolytic activity, particularly within species dominating the salterns. The appearance of antibacterial potential under stress conditions was seen in the similar pattern of fungal species as for hemolysis. The active extracts exclusively affected the growth of the Gram-positive bacterium tested, Bacillus subtilis. None of the extracts tested showed inhibition of acetylcholinesterase activity

Occurrence, Diversity and Anti-Fungal Resistance of Fungi in Sand of an Urban Beach in Slovenia—Environmental Monitoring with Possible Health Risk Implications

This article belongs to the Special Issue Fungal Diversity in Europe.Beach safety regulation is based on faecal indicators in water, leaving out sand and fungi, whose presence in both matrices has often been reported. To study the abundance, diversity and possible fluctuations of mycobiota, fungi from sand and seawater were isolated from the Portorož beach (Slovenia) during a 1-year period. Sand analyses yielded 64 species of 43 genera, whereas seawater samples yielded 29 species of 18 genera. Environmental and taxonomical data of fungal communities were analysed using machine learning approaches. Changes in the air and water temperature , sunshine hours, humidity and precipitation, air pressure and wind speed appeared to affect mycobiota. The core genera Aphanoascus, Aspergillus, Fusarium, Bisifusarium, Penicillium, Tala-romyces, and Rhizopus were found to compose a stable community within sand, although their presence and abundance fluctuated along with weather changes. Aspergillus spp. were the most abundant and thus tested against nine antimycotics using Sensititre Yeast One kit. Aspergillus niger and A. welwitschiae isolates were found to be resistant to amphotericin B. Additionally, four possible human pollution indicators were isolated during the bathing season, including Meyerozyma, which can be used in beach microbial regulation. Our findings provide the foundations for additional research on sand and seawater mycobiota and show the potential effect of global warming and extreme weather events on fungi in sand and sea.The work of Monika Novak Babiˇc was supported by Slovenian Research Agency (ARRS) through the postdoctoral research project (grant number Z7-2668) and the research program, grant number P1-0198. The work of Sašo Džeroski was supported by Slovenian Research Agency (ARRS) through the program Knowledge Technologies (grant number P2-0103). The work of João Brandão received financial support from CESAM (UID/AMB/50017-POCI-01-0145-FEDER-007638) and CITAB (UID/AGR/04033/2019), via FCT/MCTES, from national funds (PIDDAC), co-founded by FEDER, (PT2020 Partnership Agreement and Compete 2020)info:eu-repo/semantics/publishedVersio

Expression of fatty-acid-modifying enzymes in the halotolerant black yeast Aureobasidium pullulans (de Bary) G. Arnaud under salt stress

AbstractMultiple tolerance to stressful environmental conditions of the black, yeast-like fungus Aureobasidium pullulans is achieved through different adaptations, among which there is the restructuring of the lipid composition of their membranes. Here, we describe three novel genes encoding fatty-acid-modifying enzymes in A. pullulans, along with the levels of their mRNAs under different salinity conditions. High levels of Δ 9−desaturase and Δ12−desaturase mRNAs were seen at high salinities, which were consistent with an increased desaturation of the fatty acids in the cell membranes. Elevated levels of elongase mRNA were also detected. Surprisingly, increases in the levels of these mRNAs were also seen following hypo-osmotic shock, while hyperosmotic shock had exactly the opposite effect, demonstrating that data that are obtained from up-shift and down-shift salinity studies should be interpreted with caution

FT-Raman Analysis of Cellulose based Museum Textiles: Comparison of Objects Infected and Non-infected by Fungi

It is well-known fact that the supermolecular structure of museum textiles changes during aging and biodeterioration. These structural changes can be observed by different spectroscopic methods such as FT-IR, FT-Raman, and dispersive Raman spectroscopy. The purpose of the presented research is to present the usability of FT-Raman spectroscopy method for the analysis of the cellulose structure of the biodeteriorated historical textile fibers. Although historical textiles have already been analyzed using FT-Raman spectroscopy the method has been rarely used to analyze the changes of supermolecular structure of the biodeteriorated historical textiles attacked by microorganisms. In the research, cellulose textile samples from different museums and religious institutions were analyzed. Contemporary and historical cellulose textiles were scanned by FT-Raman spectra of reference and compared to determine the supermolecular cellulose fiber structure of each material. It has been shown that structural changes such as depolymerization and crystallinity changes can be detected using FT-Raman spectroscopy. The supermolecular changes of the cellulose fiber structure have been detected in biodeteriorated as well as in historical objects not infected by microorganisms. In the spectra of biodeteriorated objects, more intensive changes of spectral features were observed compared to spectra of non-infected samples. The changes were more pronounced at the museum objects made of flax. It can be concluded that biodeterioration causes more intensive structural changes than aging. On the basis of the research work, it has been shown that FT-Raman spectroscopy method can be used for the analysis of supermolecular structure changes of cellulose textiles

Production of Secondary Metabolites in Extreme Environments: Food- and Airborne Wallemia spp. Produce Toxic Metabolites at Hypersaline Conditions

<div><p>The food- and airborne fungal genus <i>Wallemia</i> comprises seven xerophilic and halophilic species: <i>W</i>. <i>sebi</i>, <i>W</i>. <i>mellicola</i>, <i>W</i>. <i>canadensis</i>, <i>W</i>. <i>tropicalis</i>, <i>W</i>. <i>muriae</i>, <i>W</i>. <i>hederae</i> and <i>W</i>. <i>ichthyophaga</i>. All listed species are adapted to low water activity and can contaminate food preserved with high amounts of salt or sugar. In relation to food safety, the effect of high salt and sugar concentrations on the production of secondary metabolites by this toxigenic fungus was investigated. The secondary metabolite profiles of 30 strains of the listed species were examined using general growth media, known to support the production of secondary metabolites, supplemented with different concentrations of NaCl, glucose and MgCl₂. In more than two hundred extracts approximately one hundred different compounds were detected using high-performance liquid chromatography-diode array detection (HPLC-DAD). Although the genome data analysis of <i>W</i>. <i>mellicola</i> (previously <i>W</i>. <i>sebi sensu lato</i>) and <i>W</i>. <i>ichthyophaga</i> revealed a low number of secondary metabolites clusters, a substantial number of secondary metabolites were detected at different conditions. Machine learning analysis of the obtained dataset showed that NaCl has higher influence on the production of secondary metabolites than other tested solutes. Mass spectrometric analysis of selected extracts revealed that NaCl in the medium affects the production of some compounds with substantial biological activities (wallimidione, walleminol, walleminone, UCA 1064-A and UCA 1064-B). In particular an increase in NaCl concentration from 5% to 15% in the growth media increased the production of the toxic metabolites wallimidione, walleminol and walleminone.</p></div