Summary
The black yeast Aureobasidium pullulans is a textbook example of a generalistic and ubiquitous fungus thriving in a wide variety of environments. To investigate whether A. pullulans is a true ...generalist, or alternatively, whether part of its versatility can be attributed to intraspecific specialization masked by cryptic diversification undetectable by traditional phylogenetic analyses, we sequenced and analysed the genomes of 50 strains of A. pullulans from different habitats and geographic locations. No population structure was observed in the sequenced strains. Decay of linkage disequilibrium over shorter physical distances (<100 bp) than in many sexually reproducing fungi indicates a high level of recombination in the species. A homothallic mating locus was found in all of the sequenced genomes. Aureobasidium pullulans appears to have a homogeneous population genetics structure, which is best explained by good dispersal and high levels of recombination. This means that A. pullulans is a true generalist that can inhabit different habitats without substantial specialization to any of these habitats at the genomic level. Furthermore, in the future, the high level of A. pullulans recombination can be exploited for the identification of genomic loci that are involved in the many biotechnologically useful traits of this black yeast.
Abstract
Mycosporines and mycosporine-like amino acids (MAAs) are low-molecular-weight water-soluble molecules absorbing UV radiation in the wavelength range 310–365 nm. They are accumulated by a ...wide range of microorganisms, prokaryotic (cyanobacteria) as well as eukaryotic (microalgae, yeasts, and fungi), and a variety of marine macroalgae, corals, and other marine life forms. The role that MAAs play as sunscreen compounds to protect against damage by harmful levels of UV radiation is well established. However, evidence is accumulating that MAAs may have additional functions: they may serve as antioxidant molecules scavenging toxic oxygen radicals, they can be accumulated as compatible solutes following salt stress, their formation is induced by desiccation or by thermal stress in certain organisms, they have been suggested to function as an accessory light-harvesting pigment in photosynthesis or as an intracellular nitrogen reservoir, and they are involved in fungal reproduction. Here, the evidence for these additional roles of MAAs as ‘multipurpose’ secondary metabolites is reviewed, with special emphasis on their functions in the microbial world.
Modernisation of our households created novel opportunities for microbial growth and thus changed the array of microorganisms we come in contact with. While many studies have investigated ...microorganisms in the air and dust, tap water, another major input of microbial propagules, has received far less attention. The quality of drinking water in developed world is strictly regulated to prevent immediate danger to human health. However, fungi, algae, protists and bacteria of less immediate concern are usually not screened for. These organisms can thus use water as a vector of transmission into the households, especially if they are resistant to various water treatment procedures. Good tolerance of unfavourable abiotic conditions is also important for survival once microbes enter the household. Limitation of water availability, high or low temperatures, application of antimicrobial chemicals and other measures are taken to prevent indoor microbial overgrowth. These conditions, together with a large number of novel chemicals in our homes, shape the diversity and abundance of indoor microbiota through constant selection of the most resilient species, resulting in a substantial overlap in diversity of indoor and natural extreme environments. At least in fungi, extremotolerance has been linked to human pathogenicity, explaining why many species found in novel indoor habitats (such as dishwasher) are notable opportunistic pathogens. As a result, microorganisms that often enter our households with water and are then enriched in novel indoor habitats might have a hitherto underestimated impact on the well-being of the increasingly indoor-bound human population.
Key points
Domestic environment harbours a large diversity of microorganisms.
Microbiota of water-related indoor habitats mainly originates from tap water.
Bathrooms, kitchens and household appliances select for polyextremotolerant species.
Many household-related microorganisms are human opportunistic pathogens.
Deciphering the genetic code of organisms with unusual phenotypes can help answer fundamental biological questions and provide insight into mechanisms relevant to human biomedical research. The cave ...salamander Proteus anguinus (Urodela: Proteidae), also known as the olm, is an example of a species with unique morphological and physiological adaptations to its subterranean environment, including regenerative abilities, resistance to prolonged starvation, and a life span of more than 100 years. However, the structure and sequence of the olm genome is still largely unknown owing to its enormous size, estimated at nearly 50 gigabases. An international Proteus Genome Research Consortium has been formed to decipher the olm genome. This perspective provides the scientific and biomedical rationale for exploring the olm genome and outlines potential outcomes, challenges, and methodological approaches required to analyze and annotate the genome of this unique amphibian.
An international Proteus Genome Research Consortium has been formed to decipher the genome of Proteus anguinus (the olm). This perspective provides the scientific and biomedical rationale for exploring the olm genome and outlines potential outcomes, challenges, and methodological approaches required to analyze and annotate the genome of this unique amphibian.
The difference in antagonistic activity against the causal agent of grey mould (Botrytis cinerea) of tomato between Aureobasidium strains belonging to three different species, namely A. pullulans, A. ...melanogenum and A. subglaciale, was evaluated by in vitro and in vivo assays. In the yeast–pathogen direct interaction experiment, all the strains significantly reduced B. cinerea growth, with A. melanogenum the least efficient species (17.8% of reduction) compared to A. pullulans and subglaciale (22 and 27.8%). The non‐volatile metabolites produced by all three species reduced mycelial growth between 95 and 100%. These metabolites were characterised by FT‐IR spectroscopy as polysaccharides, lytic enzymes, siderophores and antibiotics. The inhibitory effect of Aureobasidium strains on pathogenic enzymes such as xylanase, polygalacturonase and pectinase was measured showing A. pullulans strains as capable of strong inhibition of xylanase, an enzyme directly related to the virulence of necrotrophic pathogens such as B. cinerea. Our data demonstrate that the different species of Aureobasidium isolated from a range of non‐conventional environments exerted variable efficacy against B. cinerea, with A. pullulans as the most active species followed by A. subglaciale and A. melanogenum as ineffective and not suitable for biocontrol applications.
Summary
Polycyclic aromatic hydrocarbons (PAHs) are among the most persistent xenobiotic compounds, with high toxicity effects. Mycoremediation with halophilic Aspergillus sydowii was used for their ...removal from a hypersaline medium (1 M NaCl). A. sydowii metabolized PAHs as sole carbon sources, resulting in the removal of up to 90% for both PAHs benzo a pyrene (BaP) and phenanthrene (Phe) after 10 days. Elimination of Phe and BaP was almost exclusively due to biotransformation and not adsorption by dead mycelium and did not correlate with the activity of lignin modifying enzymes (LME). Transcriptomes of A. sydowii grown on PAHs, or on glucose as control, both at hypersaline conditions, revealed 170 upregulated and 76 downregulated genes. Upregulated genes were related to starvation, cell wall remodelling, degradation and metabolism of xenobiotics, DNA/RNA metabolism, energy generation, signalling and general stress responses. Changes of LME expression levels were not detected, while the chloroperoxidase gene, possibly related to detoxification processes in fungi, was strongly upregulated. We propose that two parallel metabolic pathways (mitochondrial and cytosolic) are involved in degradation and detoxification of PAHs in A. sydowii resulting in intracellular oxidation of PAHs. To the best of our knowledge, this is the most comprehensive transcriptomic analysis on fungal degradation of PAHs.
Our planet offers many opportunities for life on the edge: high and low temperatures, high salt concentrations, acidic and basic conditions and toxic environments, to name but a few extremes. Recent ...studies have revealed the diversity of fungi that can occur in stressful environments that are hostile to most eukaryotes. We review these studies here, with the additional purpose of proposing some mechanisms that would allow for the evolutionary adaptation of eukaryotic microbial life under extreme conditions. We focus, in particular, on life in ice and life at high salt concentrations, as there is a surprising similarity between the fungal populations in these two kinds of environments, both of which are characterized by low water activity. We propose steps of evolution of generalist species towards the development of specialists in extreme habitats. We argue that traits present in some fungal groups, such as asexuality, synthesis of melanin-like pigments and a flexible morphology, are preadaptations that facilitate persistence and eventual adaptation to conditions on the ecological edge, as well as biotope switches. These processes are important for understanding the evolution of extremophiles; moreover, they have implications for the emergence of novel fungal pathogens.
The fungal genus
of the order
(Wallemiomycotina, Basidiomycota) comprises the most xerotolerant, xerophilic and also halophilic species worldwide.
spp. are found in various osmotically challenged ...environments, such as dry, salted, or highly sugared foods, dry feed, hypersaline waters of solar salterns, salt crystals, indoor and outdoor air, and agriculture aerosols. Recently, eight species were recognized for the genus
, among which four are commonly associated with foods:
,
,
and
. To date, only strains of
,
and
have been reported to be related to human health problems, as either allergological conditions (e.g., farmer’s lung disease) or rare subcutaneous/cutaneous infections. Therefore, this allergological and infective potential, together with the toxins that the majority of
spp. produce even under saline conditions, defines these fungi as filamentous food-borne pathogenic fungi.
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 and consequent damage to the paintings. We used this strategy for a deteriorated 17th century Celje Ceiling, tempera painting in a wooden frame, covering 143 m2 of the ceiling. An interdisciplinary approach, from monitoring microclimatic conditions and wood moisture content, to examinations using UV and VIS photography, analyses of paint layers and decay products by Raman and FTIR spectroscopy, SEM-EDS, and protein binders by ELISA, was used to assess current condition of the painting. Data from 535 painting's samples were subjected to analysis by machine learning methods. Moulding, the main cause of biodeterioration, was found to be strongly influenced by the position of the painting in the room and related microclimatic conditions. The presence of a coating layer, protein binders and pigments, such as goethite, ultramarine and kaolinite, had important role in mould development as well. The painting was mainly damaged by currently non-active, presumably xerophilic Aspergillus species, as determined by microscopy, cultivation and amplicon sequencing.
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•Four century-old tempera painting, Celje Cieling, covering 143 m2 of ceiling was analysed using a multidisciplinary approach.•Microclimatic conditions in the chamber and wood were monitored over three years.•Data obtained by painting analyses were subjected to machine learning to create a predictive model of further deterioration.•Microscopy, culture-dependent and -independent methods were used to assess microbial contamination in selected parts of the painting.
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