Extremely Halotolerant and Halophilic Fungi Inhabit Brine in Solar Salterns Around the Globe

Halofilne su i halotolerantne gljive već dugi niz godina poznate isključivo kao zagađivači hrane konzervirane dodavanjem velikih koncentracija soli ili šećera. Prvi je put otkriveno da gljive aktivno nastanjuju hipersalini okoliš godine 2000., kad su pronađene u umjetnim solanama u Sloveniji. Od tada su opisane gljive iz različitih solana i slanih jezera na tri kontinenta. Mikobiota što nastanjuje ova prirodno izuzetno slana staništa sastoji se od filogenetski nepovezanih halotolerantnih, izrazito halotolerantnih i halofilnih gljiva, koje su zastupljene ne samo vrstama što su otprije poznate kao zagađivači hrane, već i novim te rijetkim vrstama. Prevladavaju predstavnici različitih vrsta crnih kvasaca i srodnih melaniziranih gljiva roda Cladosporium, različitih vrsta anamorfnih rodova Aspergillus i Penicillium, teleomorfnih rodova Emericella i Eurotium, određene vrste kvasaca koje ne sadržavaju melanin, te vrste roda Wallemia. Prije otkrića i opisa autohtonih vrsta pronađenih u solanama fiziološki su i molekularni mehanizmi što određuju toleranciju eukariotskih mikroorganizama na sol proučavani pomoću modelnih organizama osjetljivih na veći salinitet. Najispitivaniji eukariotski mikroorganizam je kvasac Saccharomyces cerevisiae, koji se ne može prilagoditi izrazito slanim uvjetima. Stoga vrste izolirane iz prirodno hipersalinog okoliša, poput Debaryomyces hansenii, Aureobasidum pullulans, Hortaea werneckii i Wallemia ichthyophaga, predstavljaju prikladnije modelne organizme za ispitivanje halotolerancije eukariotskih organizama. Studije tih vrsta, a osobito izrazito halotolerantne H. werneckii i obligatno halofilne W. ichthyophaga, neprestano otkrivaju različite strategije takvih mikroorganizama za prevladavanje problema poput toksičnosti iona i malog aktiviteta vode. U fokusu je ovoga rada bilo prikazati glavne vrste gljiva što nastanjuju solane diljem svijeta i najprikladnije modelne organizme za proučavanje prilagodbe gljiva na uvjete povećanog saliniteta.For a long time halotolerant and halophilic fungi have been known exclusively as contaminants of food preserved with high concentrations of either salt or sugar. They were first reported in 2000 to be active inhabitants of hypersaline environments, when they were found in man-made solar salterns in Slovenia. Since then, they have been described in different salterns and salt lakes on three continents. The mycobiota that inhabit these natural hypersaline environments are composed of phylogenetically unrelated halotolerant, extremely halotolerant, and halophilic fungi, which are represented not only by species previously known only as food contaminants, but also by new and rare species. The dominant representatives are different species of black yeast-like and related melanized fungi of the genus Cladosporium, different species within the anamorphic Aspergillus and Penicillium, and the teleomorphic Emericella and Eurotium, certain species of non-melanized yeasts, and Wallemia spp. Until the discovery and description of indigenous saltern mycobiota, the physiological and molecular mechanisms related to salt tolerance in eukaryotic microorganisms were studied using salt-sensitive model organisms. The most studied eukaryotic microorganism was Saccharomyces cerevisiae, which cannot adapt to hypersaline conditions. Species like Debaryomyces hansenii, Aureobasidum pullulans, Hortaea werneckii and Wallemia ichthyophaga, which have now been isolated globally from natural hypersaline environments, represent more suitable model organisms for the study of halotolerance in eukaryotes. Such studies in these species, and particularly with the extremely halotolerant H. werneckii and obligately halophilic W. ichthyophaga have continued to unravel the different strategies that these microorganisms can use to cope with the problems of ion toxicity and low water activity. The focus of this review is to present the main species of fungi inhabiting solar salterns around the world and the most suitable model fungi to study adaptations to life at high salinity

Screening for Culturable Microorganisms from Cave Environments (Slovenia)

V vzorcih iz treh različnih jam smo proučevali mikroorganizme, ki jih lahko gojimo v laboratorijskih razmerah. V jami Pečina v Borštu smo prisotnost mikroorganizmov proučevali v preperelem apnencu, jamskem srebru in v jamski ponvici, kjer se na površini velikokrat pojavljajo kalcitne ploščice; v Martinski jami v preperelem apnencu, v Snežni jami na Raduhi pa kalcitno jamsko mleko. Podatki o številu mikroorganizmov so bili v nekaterih primerih dopolnjeni πe z identifikacijo širše skupine ali rodu. Rezultati kažejo, da so poleg še nekaterih drugih bakterijskih in glivnih taksonov fluorescentne pseudomonade prevladujoči mikroorganizmi.Various microenvironments in three different caves were screened for the presence of indigenous culturable microorganisms: extremely weathered limestone in Pečina v Borštu and Martinska jama, cave silver and calcite rafts on the surface of subterranean ponds in Pečina v Borštu and calcite moonmilk speleotheme in Snežna jama of Raduha mountain. The counts of viable cells collected are supplemented with laboratory data necessary to establish genus or wider taxonomic group level identity of isolates. Besides other bacterial and fungal groups flourescent pseudomonads are prevailing among isolates

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

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

The extremely halotolerant black yeast Hortaea werneckii - a model for intraspecific hybridization in clonal fungi

n/

No need for speed

Microbial growth under extreme conditions is often slow. This is partly because large amounts of energy are diverted into cellular mechanisms that allow survival under hostile conditions. Because this challenge is universal and diversity in extreme environments is low compared to non-extreme environments, slow-growing microorganisms are not overgrown by other species. In some cases, especially when nutrients are scarce, slow growth was even shown to increase stress tolerance. And in at least some species of extremotolerant and extremophilic fungi, growth rate appears to be coupled with their very unusual morphologies, which in turn may be an adaptation to extreme conditions. However, there is more than one strategy of survival in extreme environments. Fungi that thrive in extremes can be divided into (i) ubiquitous and polyextremotolerant generalists and (ii) rarely isolated specialists with narrow ecological amplitudes. While generalists can compete with mesophilic species, specialists cannot. When adapting to extreme conditions, the risk of an evolutionary trade-off in the form of reduced fitness under mesophilic conditions may limit the maximum stress tolerance achievable by polyextremotolerant generalists. At the same time, specialists are rarely found in mesophilic environments, which allows them to evolve to ever greater extremotolerance, since a reduction of mesophilic fitness is likely to have little impact on their evolutionary success

Xerophilic fungal genus Wallemia: Bioactive inhabitants of marine solar salterns and salty food

Wallemia is a genus of cosmopolitan xerophilic fungi, frequently involved in food spoilage of particularly sweet, salty, and dried food. Until recently, only a single species, Wallemia sebi, was recognized in the genus. When a large group of strains globally collected in salterns and other different ecological niches was analyzed on the level of physiological, morphological and molecular characteristics, a new basidiomycetous class, Wallemiomycetes, covering an order of Wallemiales was proposed and three Wallemia species were recognized: W. ichthyophaga, W. sebi and W. muriae. Wallemia ichthyophaga was recognized as the most halophilic eukaryote known, thus representing an appropriate eukaryotic model for in depth studies of adaptation to hypersaline conditions. Our preliminary studies indicated that all three Wallemia species synthesized a yet undescribed haemolytic compound under, surprisingly, low water activity conditions. Due to the taxonomic status w hich was unrevealed only recently, there were so far no reports on the production of any bioactive compounds by the three newly described species. The article aims to present the taxonomy, ecology, physiology and so far described molecular mechanisms of adaptations to life at low water activity, as well as bioactive potential of the genus Wallemia, a phylogenetically ancient taxon and a taxonomic maverick within Basidiomycota

The Black Yeast Exophiala dermatitidis and Other Selected Opportunistic Human Fungal Pathogens Spread from Dishwashers to Kitchens.

We investigated the diversity and distribution of fungi in nine different sites inside 30 residential dishwashers. In total, 503 fungal strains were isolated, which belong to 10 genera and 84 species. Irrespective of the sampled site, 83% of the dishwashers were positive for fungi. The most frequent opportunistic pathogenic species were Exophiala dermatitidis, Candida parapsilosis sensu stricto, Exophiala phaeomuriformis, Fusarium dimerum, and the Saprochaete/Magnusiomyces clade. The black yeast E. dermatitidis was detected in 47% of the dishwashers, primarily at the dishwasher rubber seals, at up to 106 CFU/cm2; the other fungi detected were in the range of 102 to 105 CFU/cm2. The other most heavily contaminated dishwasher sites were side nozzles, doors and drains. Only F. dimerum was isolated from washed dishes, while dishwasher waste water contained E. dermatitidis, Exophiala oligosperma and Sarocladium killiense. Plumbing systems supplying water to household appliances represent the most probable route for contamination of dishwashers, as the fungi that represented the core dishwasher mycobiota were also detected in the tap water. Hot aerosols from dishwashers contained the human opportunistic yeast C. parapsilosis, Rhodotorula mucilaginosa and E. dermatitidis (as well as common air-borne genera such as Aspergillus, Penicillium, Trichoderma and Cladosporium). Comparison of fungal contamination of kitchens without and with dishwashers revealed that virtually all were contaminated with fungi. In both cases, the most contaminated sites were the kitchen drain and the dish drying rack. The most important difference was higher prevalence of black yeasts (E. dermatitidis in particular) in kitchens with dishwashers. In kitchens without dishwashers, C. parapsilosis strongly prevailed with negligible occurrence of E. dermatitidis. F. dimerum was isolated only from kitchens with dishwashers, while Saprochaete/Magnusiomyces isolates were only found within dishwashers. We conclude that dishwashers represent a reservoir of enriched opportunistic pathogenic species that can spread from the dishwasher into the indoor biome