Polona Zalar

University of Ljubljana · Biotechnical Faculty

A significant part of our stone heritage is made of limestone. Researchers are increasingly concerned about the risk of biodeterioration of these important objects. In this article, we present an up-to-date review of the microbial diversity of biodeteriorated limestone cultural heritage (CHL). This is based on an extensive bibliographic search of t...

Fungi are important contaminants of historic canvas paintings worldwide. They can grow on both sides of the canvas and decompose various components of the paintings. They excrete pigments and acids that change the visual appearance of the paintings and weaken their structure, leading to flaking and cracking. With the aim of recognizing the most dan...

The huge amounts of keratin-rich waste generated daily by various industries, slaughterhouses, and processing plants need to be properly managed. Most keratin degradation-related research focuses on keratin from bird feathers, but a vast minority focuses on keratin from sheep wool, which also presents a serious environmental problem. In this articl...

Historically valuable canvas paintings are often exposed to conditions enabling microbial deterioration. Painting materials, mainly of organic origin, in combination with high humidity and other environmental conditions, favor microbial metabolism and growth. These preconditions are often present during exhibitions or storage in old buildings, such...

Concrete is the most used man-made material in the world. As a building material, it is characterized by solid compressive strength and durability, ease of installation and accessibility, and chemical reactivity on the one hand, and by fragility, low tensile strength and resulting cracks on the other hand. These occur due to everyday (mechano-)phys...

Water is the most important life-limiting factor on planet Earth. Most microorganisms need large quantities of water to survive, while some extremotolerant microorganisms have evolved adaptations that enable them to live at extremely limited water conditions. Water can be limited even when it appears plentiful at first sight. It can be chemically b...

Natural weathering test at two different European climatic zones were conducted to investigate simultaneously both, the fungal colonisation and weathering process of Scots pine wood (Pinus sylvestris L.). The hypothesis was that the wood performing differently in various climate conditions might affect fungal infestation. The colour changes, wettab...

The effectiveness of an oxidative biomimetic copper-pyridine system (Cu-py-H2O2) was successfully demonstrated on model textile samples of unaged and artificially aged desized cotton inoculated with pure cultures of selected fungi, isolated from historical textile objects (Bjerkandera adusta (Basidiomycota), Cladosporium sp., Chaetomium cochlioides...

Proteus anguinus is a neotenic cave salamander, endemic to the Dinaric Karst and a symbol of world natural heritage. It is classified as “vulnerable” by the International Union for Conservation of Nature (IUCN) and is one of the EU priority species in need of strict protection. Due to inaccessibility of their natural underground habitat, scientific...

Heavily pigmented glacier ice algae Ancylonema nordenskiöldii and Ancylonema alaskanum (Zygnematophyceae, Streptophyta) reduce the bare ice albedo of the Greenland Ice Sheet, amplifying melt from the largest cryospheric contributor to eustatic sea-level rise. Little information is available about glacier ice algae interactions with other microbial...

as it produces an extracellular polysaccharide, pullulan, that is used in cosmetics, medicine and the food industry [18,19], and numerous enzymes, including amylases, lipases, and hemicellulose and xylan-degrading enzymes, that have a variety of industrial applications [2,15,20,21]. In the first half of the twentieth century, this fungus, under the...

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 overgro...

Interdisciplinary investigations of damaged cultural heritage objects have nowadays become standard practise. Numerous techniques in various fields may generate large amounts of data, difficult to interpret. Machine learning was applied to data collected from samples of a painting to build a predictive model of potential further biodeterioration an...

Since the emergence of the first fungi some 700 million years ago, unicellular yeast-like forms have emerged multiple times in independent lineages via convergent evolution. While tens to hundreds of millions of years separate the independent evolution of these unicellular organisms, they share remarkable phenotypic and metabolic similarities, and...

The novel extremophilic yeast Rhodotorula frigidialcoholis, formerly R. JG1b, was isolated from ice-cemented permafrost in University Valley (Antarctic), one of coldest and driest environments on Earth. Phenotypic and phylogenetic analyses classified R. frigidialcoholis as a novel species. To characterize its cold-adaptive strategies, we performed...

Sampling campaigns in Greenland and Svalbard were executed to explore fungal diversity in cold habitats. Three very abundant groups of strains were discovered, consisting either of recently described or of yet-undescribed psychrophilic and oligotrophic yeasts and dimorphic fungi, accounting for around 50 % of the total cultivable diversity of basid...

Since the emergence of the first fungi some 700 million years ago, uni-cellular yeast-like forms have emerged multiple times in independent lineages via convergent evolution. While tens to hundreds of millions of years separate the independent evolution of these unicellular organisms, they share remarkable phenotypic and metabolic similarities, and...

The polyphyletic group of black fungi within the Ascomycota (Arthoniomycetes, Dothideomycetes, and Eurotiomycetes) is ubiquitous in natural and anthropogenic habitats. Partly because of their dark, melanin-based pigmentation, black fungi are resistant to stresses including UV-and ionizing-radiation, heat and desiccation, toxic metals, and organic p...

Lichenized fungi usually develop complex, stratified morphologies through an intricately balanced living together with their algal partners, but several species are known to form only more or less loose associations with algae. These borderline lichens are still little explored although they could inform us about early stages of lichen evolution. W...

Virusi v vodnih okoljih so bili v zadnjem desetletju intenzivno preučevani, vendar pa virusi v jamskih vodah ostajajo slabo opisani. Cilj raziskave je bila karakterizacija viroma vode vzorčene v različnih jamah, v katerih živijo tudi predstavniki vrste Proteus anguinus oziroma človeške ribice. Predstavniki dvoživk, ki živijo v tako občutljivih vodn...

Aquatic viruses have been extensively studied over the past decade, yet aspects of virus communities in cave waters remain poorly described. Our goal was to characterize viromes of cave water sampled in oligotrophic environments where Proteus anguinus, also known as olm or European cave salamander is present. Due to their dependence on, in many cas...

(1) Background: Mechanisms of cellular and molecular adaptation of fungi to salinity have been commonly drawn from halotolerant strains and few studies in basidiomycete fungi. These studies have been conducted in settings where cells are subjected to stress, either hypo- or hyperosmotic, which can be a confounding factor in describing physiological...

The polymorphic black yeast Hortaea werneckii (Capnodiales, Ascomycota) is extremely halotolerant (growth from 0 to 30% [w/v] NaCl) and has been extensively studied as a model for halotolerance in Eukaryotes for over two decades. Its most frequent sources are hypersaline environments and adjacent sea-water habitats in temperate, subtropical and tro...

Great Salt Lake, Utah, is thalassohaline, terminal lake that currently occupies the Bonneville Basin, a depression in the larger Great Basin area of the western United States. Natural processes and climate conditions create a dynamic ecosystem with shifting salinity gradients and lake levels. Great Salt Lake has also been subjected to anthropomorph...

A global set of clinical and environmental strains of the halotolerant black yeast-like fungus Hortaea werneckii are analyzed by multilocus sequencing and AFLP, and physiological parameters are determined. Partial translation elongation factor 1-α proves to be suitable for typing because of the presence/absence of introns and also the presence of s...

People in developed countries spend most of their time indoors, either in their homes or at work. They are thus exposed to a variety of microorganisms that can survive selectively in indoor environments despite of applied hygiene measures and sanitation procedures. Household appliances running at high or low temperatures and with detergents accommo...

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 metho...

Proteus anguinus is a neotenic cave amphibian endemic to the Dinaric Karst and represents a symbol of Slovenian natural heritage. It is classified as 'Vulnerable' by the International Union for Conservation of Nature (IUCN) and is one of the EU priority species in need of strict protection. Due to inaccessibility of its natural underground habitat,...

An inventory of culturable yeasts from the soil and water of natural CO2 springs (mofettes) in northeast Slovenia is presented. In mofettes, CO2 of geological origin reaches the soil surface causing temporarily and spatially stable hypoxic environments in soil and water. In total, 142 yeast strains were isolated and identified from high CO2 and con...

Background: The black yeast Hortaea werneckii (Dothideomycetes, Ascomycota) is one of the most extremely halotolerant fungi, capable of growth at NaCl concentrations close to saturation. Although dothideomycetous fungi are typically haploid, the reference H. werneckii strain has a diploid genome consisting of two subgenomes with a high level of he...

Over 80% of the Earth’s environments are permanently or periodically exposed to temperatures below 5 °C. Cold habitats harbour a wide diversity of psychrophilic and psychrotolerant yeasts. During ecological studies of yeast communities carried out in cold ecosystem in the Italian Alps, Svalbard (Norway, Arctic region), and Portugal, 23 yeast strain...

The finding of heavily damaged historic silks prompted this study to answer the title question on possible unwanted effects of fungal decontamination by gamma-irradiation. Although silk fiber constitutes of relatively stable protein fibroin heritage silk textiles need protection from biodegradation. Low-dose (0.5−2 kGy) gamma-irradiation is already...

Exophiala dermatitidis is an ascomycetous black yeast from the order Chaetothyriales. Its growth characteristics include the polymorphic life cycle, ability to grow at high and low temperatures, at a wide pH range, survival at high concentrations of NaCl, and survival at high UV and radioactive radiation. Exophiala dermatitidis causes deep or local...

Aspergillus section Restricti together with sister section Aspergillus (formerly Eurotium) comprises xerophilic species, that are able to grow on substrates with low water activity and in extreme environments. We adressed the monophyly of both sections within subgenus Aspergillus and applied a multidisciplinary approach for definition of species bo...

In modern society, people spend most of their time indoors and are exposed to a variety of selected air- and waterborne microorganisms that survive indoors despite sanitation chemicals, hygiene measures and occasional high temperatures. Although public health has focussed on bacteria and viruses, fungi are increasingly recognised as opportunistic i...

For a long time, halotolerant yeasts were known exclusively as contaminants of food preserved with high concentrations of salt or sugar. Their presence in natural thalassohaline hypersaline environments was unknown until 2000, when they were first reported to be active inhabitants of man-made solar salterns in Slovenia. Since then, they have been d...

As other amphibians kept in artificial or semi-natural environments, the specimens of troglomorphic Proteus anguinus are susceptible to opportunistic microbial infections, due to the suppressed defensive mechanisms of the host exposed to stress or suboptimal living conditions. Despite absence of published data on infection of Proteus in captivity,...

Halophilic fungal strains isolated from historical wooden staircase in a salt mine in Austria, and from wall biofilm and soil of a cave in the Coastal Range of the hyperarid Atacama Desert in Chile were characterised and described newly as Aspergillus salisburgensis and Aspergillus atacamensis. Morphological characters including solitary phialides...

The understanding of the biological, medical and technical importance of microbial biofilms continues to increase dramatically. Despite the hostile conditions in municipal and household water systems and in some common household appliances, such as dishwashers and washing machines, rich communities of extremotolerant microorganisms can develop. Few...

In the present study we describe the occurrence of fungi in 100 tap water and 16 groundwater samples from Slovenia. We used culture-dependent and culture-independent techniques. 28 fungal species belonging to 16 genera were isolated with selected culturing conditions, targeting human opportunistic yeasts and yeast-like fungi. Of special concern was...

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 d...

Background: Acetic acid is one of the major inhibitors in lignocellulose hydrolysates used for the production of second-generation bioethanol. Although several genes have been identified in laboratory yeast strains that are required for tolerance to acetic acid, the genetic basis of the high acetic acid tolerance naturally present in some Saccharo...

INTRODUCTION Over the last thirty years fungi in indoor and clinical environments have increasingly been recognized as a health problem. Reports show that one billion people around the world suffer from different fungal infections1. The European legislations for drinking water do not require l detection or monitoring of fungi2,3. In our study, we i...

The domestication of the wine yeast S. cerevisiae is thought to be contemporary with the development and expansion of viticulture along the Mediterranean basin. Until now, the unavailability of wild lineages prevented the identification of the closest wild relatives of wine yeasts. Here, we enlarge the collection of natural lineages and employ whol...

Wallemia sebi is a xerophilic food- and air-borne fungus. The name has been used for strains that prevail in cold, temperate and tropical climates. In this study, multi-locus phylogenetic analyses, using the internal transcribed spacer (ITS) regions, DNA replication licensing factor (MCM7), pre-rRNA processing protein (TSR1), RNA polymerase II larg...

Wallemia comprises air- and food-borne, mycotoxigenic contaminants including the halophilic W. ichthyophaga, xerotolerant W. sebi and xerophilic W. muriae. Wallemia isolates are easily overlooked and only a comparably small number of strains have been deposited in culture collections so far. In order to better understand the natural distribution of...

A worldwide survey of Wallemia occurring in house dust and indoor air was conducted. The isolated strains were identified as W. sebi and W. muriae. Previous studies suggested that the W. sebi phylogenetic clade contained cryptic species but conclusive evidence was lacking because only the internal transcribed spacer (ITS) marker was analyzed. The I...

The scope of this study was an analysis of the deterioration of cotton fibres caused by selected strains of fungal species from historical cotton textile objects. Aged and non-aged cotton fabric specimens were inoculated with representative strains of the six highest frequency fungal species isolated from museum textile objects from different Slove...

Energy constraints have altered consumer practice regarding the use of household washing machines. Washing machines were developed that use lower washing temperatures, smaller amounts of water and biodegradable detergents. These conditions may favour the enrichment of opportunistic human pathogenic fungi. We focused on the isolation of fungi from t...

Many species of dimorphic basidiomycetes are known only in their asexual phase and typically those pigmented in different hues of red have been classified in the large polyphyletic genus Rhodotorula. These yeasts are ubiquitous and include a few species of some clinical relevance. The phylogenetic distribution of Rhodotorula spans three classes: Mi...

Gospodinjski aparati kot so npr. pomivalni stroji predstavljajo poli-ekstremne ekološke niše. Čeprav temperature v pomivalnih strojih lahko dosežejo 74ºC in se pH lahko dvigne do 12, na račun novih ekoloških trendov in varčevanja z energijo vedno bolj uporabljamo temperature okoli 40ºC in biološko razgradljive detergente. V okviru globalne študije...

Vsak človek je upravičen do čiste pitne vode, nujno potrebne za preživetje ter vsakodnevna opravila. Evropska in slovenska direktiva o pitnih vodah predpisujeta mikrobiološke analize za detekcijo celokupnega števila aerobnih mikroorganizmov, koliformnih bakterij, bakterij Escherichia coli, Clostridium sp., za ustekleničene vode pa tudi Pseudomonas...

Skrajnostna okolja so ekološka niša s specifičnimi pogoji za življenje, z nizko mikrobno vrstno diverziteto, ki je na preživetje v takšnih razmerah dobro prilagojena ter številčneje zastopana. Skrajnostna okolja pa ne najdemo samo v naravi, temveč tudi v naših domovih. To so savne, kopalnice, kuhinje ter, kot se je izkazalo šele nedavno, tudi gospo...

Safe drinking water is essential for everyday human life. The European legislations for drinking water require microbiological analyses for the detection of bacteria like coliforms, Escherichia coli, Clostridium sp. and for bottled water also Pseudomonas sp. Regarding fungi no genera are mentioned. To meet the requirements, underground water source...

Dishwasher as potential sources of infections with human pathogenic black yeast: Plant, Human and animal pathogenesis and Disease control

Background Aureobasidium pullulans is a black-yeast-like fungus used for production of the polysaccharide pullulan and the antimycotic aureobasidin A, and as a biocontrol agent in agriculture. It can cause opportunistic human infections, and it inhabits various extreme environments. To promote the understanding of these traits, we performed de-novo...

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...

We report on the screening for biological activities of organic extracts from seven strains that represent four varieties of the fungus Aureobasidium pullulans, that is A. pullulans var. melanogenum, A. pullulans var. pullulans, A. pullulans var. subglaciale and A. pullulans var. namibiae. We monitored haemolysis, cytotoxicity, antioxidant capacity...

The Arctic area is a polar region at the northernmost part of the Earth, north of the Arctic Circle (66° 33′N). It is a region of an ice-covered Arctic ocean, surrounded by treeless permafrost. The climate within the Circle is extremely cold, and much of the area is permanently covered with ice. Unlike in the temperate zones, where filamentous fung...

Preservation of historical objects is of the utmost importance for future generations, as such objects have great social, historical, cultural and educational value. However, the preservation of organic materials often causes problems, as those involved can have little knowledge of biological decay. Fungal contaminations in particular can alter the...

BACKGROUND: Aureobasidium pullulans is a black-yeast-like fungus used for production of the polysaccharide pullulan and the antimycotic aureobasidin A, and as a biocontrol agent in agriculture. It can cause opportunistic human infections, and it inhabits various extreme environments. To promote the understanding of these traits, we performed de-nov...

Ecological niches with extreme conditions exist not only in nature, but also in our homes, in household appliances, such as dishwashers and washing machines. Extremes in appliances are often combined, due to variable temperatures, reaching up to 100 ºC, fluctuating moisture, and alcaline pH due to the addition of detergents. Acording to the global...

Extreme environments are not found only in nature, but are also created by human. For example, in our homes, many extreme ecological niches are generated inside of several household appliances. Such niches can be occupied by extremotolerant microorganisms, which may tolerate stress factors as high temperature, high or low pH and high concentration...

The aim of the research was to break the cell walls and membranes of Hortaea werneckii using SC CO2 and consecutively to release enzymes from cells with their unchanged activity after treatment.From the technical and economical reasons, microorganisms are still the most important source of enzymes. Therefore, the suspension culture of H. werneckii,...

Microbial mats are a laminated organic-sedimentary ecosystem, found in a wide range of habitats. Fluctuating diel and seasonal physicochemical gradients characterize these ecosystems, resulting in both strata and microenvironments that harbor specific microbial communities. This study was undertaken to compare two types of microbial mats across sea...

Solar salterns are constructed as shallow multi-pond systems for the production of halite through evaporation of seawater. The main feature of salterns is the discontinuous salinity gradient that provides a range of well-defined habitats with increasing salinities, from moderate to hypersaline. These present one of the most extreme environments, be...