Welcome to the IUMS 2022 Interactive Program

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In this talk we aim to provide a review on the most relevant data we have obtained in the last decade with regards to the temporal impacts of interacting climate change related abiotic factors of temperature (30, 37^oC) water availability (0.985 and 0.93 water activity (a_w) and exposure to CO₂ (400, 1000 ppm) on A. flavus when colonizing maize. Among the data we included the examination of the temporal changes in aflatoxin biosynthesis genes, global transcriptomic response of this species using RNA sequencing and effects on the metabolite profiles using LC-MS/MS. Effects of CO₂ x temperature x water stress impacted on a number of genes co-expressed in relation to temporal colonisation patterns. Co-expressed genes with a high association with modules were also correlated with increased CO₂ levels. Heat maps of temporal differential expression of the aflatoxin gene cluster genes relative to the control conditions (30^oC, 400 ppm CO₂ and 0.985 a_w) showed earlier activation at elevated temperature x CO₂ and water stress compared with control conditions. In addition, there was a stimulation of temporal aflatoxin B₁ (AFB₁) by A. flavus, especially under water stress + elevated CO₂ or temperature. There was also a change in the relative production of AFB₁ and aflatoxin B₂ (AFB₂) and cyclopiazonic acid (CPA). Under elevated temperature and CO₂ at both a_w levels, there was a stimulation of CPA relative to the AF’s. Production of up to 20 secondary metabolites showed that there was a switch in clusters of compounds during the early stages of colonization. These included from 3-nitropropionic acid to kojic acid and CPA. These results help in understanding the relationship between climate-related abiotic factors and functional effects on A. flavus in stored maize.

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Due to their high adaptability and resilience, filamentous fungi are widespread throughout the
world. In recent years there has been a sharp increase in fungal infections in humans and animals
and contaminations of crops, as well as the development of resistance to common fungicides
and antifungals. In particular, fungi that produce toxic secondary metabolites such as
mycotoxins are of concern from a food safety perspective.

Especially in regions of the world with humid climates, epidemic outbreaks of mycotoxicosis
are regularly described. In addition, climate change favors the spread and migration of
pathogenic and mycotoxic fungal species. Evidence suggests that the production of secondary
metabolites by fungi may thereby be viewed as a form of compensation for unfavorable
conditions to which the fungus is exposed, and thus may support adaptation to, for example,
new temperature regimes and competing microbial populations. Understanding the
physiological drivers behind the formation of a particular secondary metabolite by the fungus
will allow the development of strategies to reduce it.

But, if the production of a metabolite offers a survival advantage for the fungus, then there is a
selection pressure to maintain the formation of this metabolite. This is an important aspect in
the development of sustainable prevention strategies against fungal infestation and mycotoxin
contamination.

Background and Aims

Aspergillus is an important genus of filamentous fungi with more than 400 accepted species and a large number of newly described species every year.

Recent taxonomic studies dealing with the section Flavipedes left some confusion and several new species were recently described so we decided to clarify the taxonomy of this section with a proper revision.

The number of species in series Versicolores rose to 17 in recent years, however, the identification to species level is problematic even if molecular methods are used.

Methods

We have revised the section Flavipedes and series Versicolores using modern species delimitation methods (several single-locus and one multi-locus method) and traditional morphological analysis. In the case of section Flavipedes, we used a dataset of 90 strains and partial DNA sequences of three genes. For series Versicolores, we employed an extensive dataset of more than 500 calmodulin sequences and a reduced dataset of 215 strains and partial DNA sequences of five genes.

Results

In section Flavipedes, we described four new species and synonymized one of the accepted species, so the section currently harbors 18 species.

The analysis of our large dataset of series Versicolores members resulted in a dramatic reduction of species number from 17 to four. Despite the reduction in species count, phenotype-based identification remains challenging.

Conclusions

We have clarified the taxonomy of section Flavipedes and increased its known phylogenetic and morphological variability.

The results of series Versicolores revision with an unprecedented large dataset revealed the importance of sampling in taxonomic studies.

Background and Aims

Aspergillus niger is the most commonly reported etiology of otomycosis based on morphological characteristics. This fungus is a member of Aspergillus section Nigri, a set of morphologically indistinguishable species that can harbor various antifungal susceptibility patterns. The aim of this study was to accurately identify and determine the susceptibility pattern of a set of black aspergilli isolated from otomycosis patients.

Methods

Forty-three black Aspergillus isolates from otomycosis patients were identified by using the PCR-sequencing of the b-tubulin gene. Furthermore, the susceptibility of isolates to three antifungal drugs, including fluconazole (FLU), clotrimazole (CLT) and nystatin (NS), were tested according to CLSI M38-A2. The data were analyzed using the SPSS software (version 15).

Results

The majority of isolates were identified as A. tubingensis (32/43, 74.42%) followed by A. niger (11/43, 25.58%). The lowest minimum inhibitory concentration (MIC) values were observed for NS with geometric means (GM) of 4.65 mg/mL and 4.83 mg/mL against A. tubingensis and A. niger isolates, respectively. CLT showed wide MIC ranges and a statistically significant inter-species difference was observed between A. tubingensis and A. niger isolates (P < 0.05). FLU was inactive against both species with GMs > 64 mg/mL.

Conclusions

Species other than A. niger can be more frequent as observed in our study. In addition, considering the low and variable activity of tested antifungal drugs, empirical treatment can result in treatment failure. Accurate identification and antifungal susceptibility testing of isolates is, however, recommended.