The role of food preservatives in shaping metabolic profile and chemical sensitivity of fungi - an extensive study on crucial mycological food contaminants from the genus Neosartorya (Aspergillus spp.)

Food preservatives are crucial in fruit production, but fungal resistance is a challenge. The main objective was to compare the sensitivity of Neosartorya spp. isolates to preservatives used in food security applications and to assess the role of metabolic properties in shaping Neosartorya spp. resistance. Sodium metabisulfite, potassium sorbate, sodium bisulfite and sorbic acid showed inhibitory effects, with sodium metabisulfite the most effective. Tested metabolic profiles included fungal growth intensity and utilization of amines and amides, amino acids, polymers, carbohydrates and carboxylic acids. Significant decreases in the utilization of all tested organic compound guilds were observed after fungal exposure to food preservatives compared to the control. Although the current investigation was limited in the number of predominately carbohydrate substrates and the breadth of metabolic responses, extensive sensitivity panels are logical step in establishing a course of action against spoilage agents in food production being important approach for innovative food chemistry.

The wood decay fungus Cerrena unicolor adjusts its metabolism to grow on various types of wood and light conditions

Cerrena unicolor is a wood-degrading basidiomycete with ecological and biotechnological importance. Comprehensive Biolog-based analysis was performed to assess the metabolic capabilities and sensitivity to chemicals of C. unicolor FCL139 growing in various sawdust substrates and light conditions. The metabolic preferences of the fungus towards utilization of specific substrates were shown to be correlated with the sawdust medium applied for fungus growth and the light conditions. The highest catabolic activity of C. unicolor was observed after fungus precultivation on birch and ash sawdust media. The fungus growing in the dark showed the highest metabolic activity which was indicated by capacity to utilize a broad spectrum of compounds and the decomposition of 74/95 of the carbon sources. In all the culture light conditions, p-hydroxyphenylacetic acid was the most readily metabolized compound. The greatest tolerance to chemicals was also observed during C. unicolor growth in darkness. The fungus was the most sensitive to nitrogen compounds and antibiotics, but more resistant to chelators. Comparative analysis of C. unicolor and selected wood-decay fungi from different taxonomic and ecological groups revealed average catabolic activity of the fungus. However, C. unicolor showed outstanding capabilities to catabolize salicin and arbutin. The obtained picture of C. unicolor metabolism showed that the fungus abilities to decompose woody plant material are influenced by various environmental factors.

The impact of Andean Patagonian mycoflora in the search for new lead molecules

Secondary metabolites from fungi have become a major source of chemical innovation in programs searching for lead molecules with bioactivities, especially over the last 50 years. In this review, we discuss the fundamental considerations in the discovery of molecules for agricultural and medicinal uses. This group of organisms possesses a strong potential for scientific and industrial communities. Recently, the incorporation of new technologies for the artificial cultivation of fungi and the use of better equipment to isolate and identify active metabolites has allowed the discovery of leading molecules for the design of new and safer drugs and pesticides. The geographical region including the Patagonian Andes mountains harbors a wide diversity of fungi, many of them still unknown and so far associated with Chilean-Argentinian Andean endemic forests. There have been very few chemical studies of the fungi located in this region. However, those few studies have allowed the discovery of new molecules. We argue that the richness of fungal biodiversity in this region offers an interesting source for the discovery of bioactive molecules for the basic and applied sciences.

Phenotype MicroArray™ system in the study of fungal functional diversity and catabolic versatility

Fungi cover a range of important ecological functions associated with nutrient and carbon cycling in leaf litter and soil. As a result, research on existing relationships between fungal functional diversity, decomposition rates and competition is of key interest. Indeed, availability of nutrients in soil is largely the consequence of organic matter degradation dynamics. The Biolog^® Phenotype MicroArrays™ (PM) system allows for the testing of fungi against many different carbon sources at any one time. The use and potential of the PM system as a tool for studying niche overlap and catabolic versatility of saprotrophic fungi is discussed here, and examples of its application are provided.

Carbon source utilization by the marine Dendryphiella species D. arenaria and D. salina

Carbon utilization by the marine Dendryphiella species, D. arenaria and D. salina, was investigated to detect differences in utilization and traits associated with their adaptation to the marine habitat. Fifty-four strains were isolated world-wide and tested for the utilization of various carbon sources using BIOLOG phenotype MicroArray (PM) and for the production of extracellular enzymes on solid culture media and on API ZYM assay strips. PM analysis showed that the fastest growth occurred on several monosaccharides and amino acids, 2-keto-d-gluconic acid, succinamide and turanose. Some polyols were poor carbon sources. However, the two species differed in their utilization rates of carbon sources, forming three major clusters: two separate clusters for D. arenaria and D. salina and a third cluster in which strains of the two species formed separate subclades that correlated with geographic origin. Several carbon sources were also found useful in differentiating the two speices. Dendryphiella salina did not utilize xylitol and quinic acid, whereas D. arenaria grew well on these substrates. The latter failed to grow on sorbitol and grew slowly on mannitol, both were good substrates for the former. There were also no qualitative differences between the extracellular enzymes produced, although laccase and peroxidase activities were confined only to some strains. The physiological similarities exhibited by the two species support the close relationship between D. arenaria and D. salina.

The influence of genotypic variation on metabolite diversity in populations of two endophytic fungal species

The relationship between metabolite production and genotypic diversity in two endophytic fungi was investigated. We selected populations of Cylindrocarpon destructans and Heliscus lugdunensis from the roots of a single tree. A total of 49 isolates of both species were selected and classified by simple genotypic tests (random amplified polymorphic DNA analysis and rDNA-ITS sequencing). In a blind test, the ability of these fungi to produce natural products was tested by ethyl acetate extraction of hyphae and culture filtrates, followed by high-performance liquid chromatography analysis (HPLC). A positive relationship was found between genotype classification and the pattern of natural products produced by a given isolate. To test the robustness of this correlation, a discriminate selection procedure was carried out by collecting fungal isolates from a second site and selecting a sub-set of the population, on the basis of genotypic variability. This sub-set of fungal isolates produced greater numbers of unique metabolites than those selected indiscriminately.

Genetic polymorphisms in three subtilisin-like protease isoforms (Pr1A, Pr1B, and Pr1C) from Metarhizium strains

Restriction fragment length polymorphisms (RFLP) were examined in three isoforms of a gene family encoding subtilisin-like proteases (Pr1A, Pr1B, and Pr1C) in several isolates of the entomopathogenic fungus Metarhizium anisopliae. RFLP variation was not observed in any of the Pr1 genes from isolates within the same genetically related group. Between genetically related groups and between isolates from disparate geographical areas, the greatest variation in RFLP patterns was observed for Pr1A. When variation does occur at Pr1B and Pr1C, it was generally observed at an EcoRI site. Metarhizium anisopliae var. majus strain 473 and a M. flavoviride isolate were most dissimilar in RFLP patterns at all Pr1 genes when compared to the M. anisopliae strains. We suggest that Pr1 genes represent a gene family of subtilisin-like proteases and that the Pr1A gene encodes for the ancestral subtilisin-like protease which has subsequently duplicated and rearranged within the genome.

Biosynthetically diverse compounds from a saltwater culture of sponge-derived Aspergillus niger

The new compound, asperic acid (1), and the known compounds hexylitaconic acid (2), malformin C (3), pyrophen (4), and asperazine (5) were isolated from the saltwater culture of Aspergillus niger derived from a Caribbean sponge, Hyrtios proteus. The structure elucidation of asperic acid is presented.

Genotypic variations among isolates ofMarasmius quercophilus, a white-rot fungus isolated from evergreen oak litter

Marasmius quercophilus is a white-rot basidiomycete isolated from evergreen oak litter. This fungus plays an extensive role in litter degradation because of its cellulase, pectinase, and laccase production. Our objective was to investigate the potential genotypic polymorphism of this species using RAPD (random amplified polymorphic DNA) and the amplification and the sequencing of fragments ITS (internal transcribed spacer) from the rRNA repeat. An intraspecies polymorphism was observed for the M. quercophilus isolates studied as suggested by the tree found with RAPD data: seven subgroups were defined. The minimum similarity coefficient observed in these groups was 0.278. The sizes of fragments ITS 1 and ITS 2 were the same for each isolate (ITS 1: 320 bp and ITS 2: 450 bp), and the percentages of nucleotide variation were 1.25 and 1.11%, respectively. Few isolates from the studied population had the same RAPD pattern that would suggest a clonal development in some zones of the site of La Gardiole.Key words: Marasmius quercophilus, intraspecific variability, ITS, RAPD.