Aspergillus Section Flavi, Need for a Robust Taxonomy.
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ABSTRACT:
SUBMITTER: Arias RS
PROVIDER: S-EPMC8638576 | biostudies-literature | 2021 Dec
REPOSITORIES: biostudies-literature
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Aspergillus Section Flavi, Need for a Robust Taxonomy.
Arias Renee S RS Orner Valerie A VA Martinez-Castillo Jaime J Sobolev Victor S VS
Microbiology resource announcements 20211202 48
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Project description:Aflatoxins and ochratoxins are among the most important mycotoxins of all and producers of both types of mycotoxins are present in Aspergillus section Flavi, albeit never in the same species. Some of the most efficient producers of aflatoxins and ochratoxins have not been described yet. Using a polyphasic approach combining phenotype, physiology, sequence and extrolite data, we describe here eight new species in section Flavi. Phylogenetically, section Flavi is split in eight clades and the section currently contains 33 species. Two species only produce aflatoxin B1 and B2 (A. pseudotamarii and A. togoensis), and 14 species are able to produce aflatoxin B1, B2, G1 and G2: three newly described species A. aflatoxiformans, A. austwickii and A. cerealis in addition to A. arachidicola, A. minisclerotigenes, A. mottae, A. luteovirescens (formerly A. bombycis), A. nomius, A. novoparasiticus, A. parasiticus, A. pseudocaelatus, A. pseudonomius, A. sergii and A. transmontanensis. It is generally accepted that A. flavus is unable to produce type G aflatoxins, but here we report on Korean strains that also produce aflatoxin G1 and G2. One strain of A. bertholletius can produce the immediate aflatoxin precursor 3-O-methylsterigmatocystin, and one strain of Aspergillus sojae and two strains of Aspergillus alliaceus produced versicolorins. Strains of the domesticated forms of A. flavus and A. parasiticus, A. oryzae and A. sojae, respectively, lost their ability to produce aflatoxins, and from the remaining phylogenetically closely related species (belonging to the A. flavus-, A. tamarii-, A. bertholletius- and A. nomius-clades), only A. caelatus, A. subflavus and A. tamarii are unable to produce aflatoxins. With exception of A. togoensis in the A. coremiiformis-clade, all species in the phylogenetically more distant clades (A. alliaceus-, A. coremiiformis-, A. leporis- and A. avenaceus-clade) are unable to produce aflatoxins. Three out of the four species in the A. alliaceus-clade can produce the mycotoxin ochratoxin A: A. alliaceus s. str. and two new species described here as A. neoalliaceus and A. vandermerwei. Eight species produced the mycotoxin tenuazonic acid: A. bertholletius, A. caelatus, A. luteovirescens, A. nomius, A. pseudocaelatus, A. pseudonomius, A. pseudotamarii and A. tamarii while the related mycotoxin cyclopiazonic acid was produced by 13 species: A. aflatoxiformans, A. austwickii, A. bertholletius, A. cerealis, A. flavus, A. minisclerotigenes, A. mottae, A. oryzae, A. pipericola, A. pseudocaelatus, A. pseudotamarii, A. sergii and A. tamarii. Furthermore, A. hancockii produced speradine A, a compound related to cyclopiazonic acid. Selected A. aflatoxiformans, A. austwickii, A. cerealis, A. flavus, A. minisclerotigenes, A. pipericola and A. sergii strains produced small sclerotia containing the mycotoxin aflatrem. Kojic acid has been found in all species in section Flavi, except A. avenaceus and A. coremiiformis. Only six species in the section did not produce any known mycotoxins: A. aspearensis, A. coremiiformis, A. lanosus, A. leporis, A. sojae and A. subflavus. An overview of other small molecule extrolites produced in Aspergillus section Flavi is given.
| S-EPMC6080641 | biostudies-literature
Project description:Increased frequencies of Aspergillus section Flavi and aflatoxins in cereal grains have been seen in recent years due to changes in climate circumstances, such as high temperatures and drought. To assess the microbiological risks of contamination, it is critical to have a reliable and accurate means of identifying the fungi. The main goal of this study was to characterize Aspergillus species from section Flavi obtained from twenty-three samples of barley and maize grains, gathered from different markets in Qena, Egypt, using morphological and molecular techniques. Twenty-three isolates were chosen, one isolate from each sample; they were identified as A. aflatoxiformans (4 isolates), A. flavus (18), and A. parasiticus (1). The existence of four aflatoxin biosynthesis genes was also investigated in relation to the strains' ability to produce total aflatoxins and aflatoxin B1, focusing on the regulatory gene aflR and the structural genes aflD and aflM. All strains producing aflatoxins were linked to the presence of aflR1 and/or aflR2, except two isolates that exhibited aflatoxins but from which aflR1 or aflR2 were not detected, which may be due to one or more missing or unstudied additional genes involved in aflatoxin production. AflD and aflM genes were amplified by 10 and 9 isolates, respectively. Five samples of barley and maize were contaminated by aflatoxins. Fifteen isolates were positive for producing total aflatoxins in the range of 0.1-240 ppm. Antagonistic activity of Trichoderma viride against A. flavus (F5) was assessed at 31.3%. Trichoderma reduced total aflatoxins in all treated seeds, particularly those subjected to Trichoderma formulation.
| S-EPMC10834605 | biostudies-literature
Project description:Aspergillus ustus is a very common species in foods, soil and indoor environments. Based on chemical, molecular and morphological data, A. insuetus is separated from A. ustus and revived. A. insuetus differs from A. ustus in producing drimans and ophiobolin G and H and not producing ustic acid and austocystins. The molecular, physiological and morphological data also indicated that another species, A. keveiisp. nov. is closely related but distinct from A. insuetus. Aspergillus section Usti sensu stricto includes 8 species: A. ustus, A. puniceus, A. granulosus, A. pseudodeflectus, A. calidoustus, A. insuetus and A. keveii together with Emericella heterothallica.
| S-EPMC2275196 | biostudies-literature
Project description:Aspergillus section Sparsi includes species which have large globose conidial heads with colours ranging from light grey to olive-buff. In this study, we examined isolates of species tentatively assigned to section Sparsi using a polyphasic approach. The characters examined include sequence analysis of partial β-tubulin, calmodulin and ITS sequences of the isolates, morphological and physiological tests, and examination of the extrolite profiles. Our data indicate that the revised section Sparsi includes 10 species: A. anthodesmis, A. biplanus, A. conjunctus, A. diversus, A. funiculosus, A. implicatus, A. panamensis, A. quitensis, A. sparsus, and the new taxon A. haitiensis. The recently described A. quitensis and A. ecuadorensis are synonyms of A. amazonicus based on both molecular and physiological data. The white-spored species A. implicatus has also been found to belong to this section. Aspergillus haitiensis sp. nov. is characterised by whitish colonies becoming reddish brown due to the production of conidial heads, and dark coloured smooth stipes. The taxon produces gregatins, siderin and several unknown but characteristic metabolites.
| S-EPMC3348776 | biostudies-literature
Project description:Section Flavi encompasses both harmful and beneficial Aspergillus species, such as Aspergillus oryzae, used in food fermentation and enzyme production, and Aspergillus flavus, food spoiler and mycotoxin producer. Here, we sequence 19 genomes spanning section Flavi and compare 31 fungal genomes including 23 Flavi species. We reassess their phylogenetic relationships and show that the closest relative of A. oryzae is not A. flavus, but A. minisclerotigenes or A. aflatoxiformans and identify high genome diversity, especially in sub-telomeric regions. We predict abundant CAZymes (598 per species) and prolific secondary metabolite gene clusters (73 per species) in section Flavi. However, the observed phenotypes (growth characteristics, polysaccharide degradation) do not necessarily correlate with inferences made from the predicted CAZyme content. Our work, including genomic analyses, phenotypic assays, and identification of secondary metabolites, highlights the genetic and metabolic diversity within section Flavi.
| S-EPMC7046712 | biostudies-literature
Project description:Microfungal isolates were routinely identified depending on both macro and micro morphological characteristics, sometimes, some fungal isolates appeared to be similar and such cases caused severe confusion for mycologists during the preliminary identification. During our previous studies dealing with isolation of fungi for some biotechnological applications; two mystifying species Aspergillus flavus and Aspergillus oryzae showed similar cultural and macroscopic features. Therefore, the current study aimed to easily distinguish between these two species depending on simple approaches which are routinely followed by a large segment of researchers. Investigation of the macroscopic features was performed to check the fungal growth on four different media (PDA, MEA, YES, and CYA) followed by microscopic examination using an ordinary light microscope, and scanning electron microscope SEM. Also, screening of secondary metabolites for both strains was preliminarily identified to find out the difference between their metabolic profiles. Finally, ITS rDNA was involved to clarify the molecular differences along their partial sequence. Conclusively, the BLAST strategy confirmed the similarity of ITS rDNA segments of both fungal strains that supported our hypothesis. The color of the fungal growth is a very critical factor whereas it is extensively influenced by the type of cultivation media. Accordingly, the YES medium was an inspiring tool assisting in prompt differentiation during the culture investigation step whereas A. oryzae and A. flavus appeared significant mustard yellow and olive green respectively. During the microscopic examination, the CYA medium also had a robust effect on the formation of the conidial chain whereas the knit long chain was observed in A. oryzae while the conidia appeared scattered and not in a chain in the case of A. flavus. Likewise, both two strains possessed different metabolic profiles where A. oryzae is not an Afla toxin producer, unlike A. flavus.
| S-EPMC10015910 | biostudies-literature
Project description:Spices are used extensively in Lebanon not only to flavour foods but also for their medicinal properties. To date, no data are available regarding the nature of the toxigenic fungal species that may contaminate these products at the marketing stage in this country. Eighty samples corresponding to 14 different types of spices were collected throughout Lebanon to characterize the Aspergillus section Flavi contaminating spices marketed in Lebanon and the toxigenic potential of these fungal species. Most fungal genera and species were identified as belonging to Aspergillus section Flavi. Aspergillus flavus was the most frequent species, representing almost 80% of the isolates. Although identified as A. flavus by molecular analysis, some strains displayed atypical morphological features. Seven strains of A. tamarii and one A. minisclerotigenes were also isolated. Analyses of toxigenic potential demonstrated that almost 80% of strains were able to produce mycotoxins, 47% produced aflatoxins, and 72% produced cyclopiazonic acid, alone or in combination with aflatoxins.
| S-EPMC6437153 | biostudies-literature
Project description:The fungal genus Aspergillus contains a diversity of species divided into taxonomic sections of closely related species. Section Flavi contains 33 species, many of industrial, agricultural, or medical relevance. Here, we analyze the mitochondrial genomes (mitogenomes) of 20 Flavi species-including 18 newly assembled mitogenomes-and compare their evolutionary history and codon usage bias patterns to their nuclear counterparts. Codon usage bias refers to variable frequencies of synonymous codons in coding DNA and is shaped by a balance of neutral processes and natural selection. All mitogenomes were circular DNA molecules with highly conserved gene content and order. As expected, genomic content, including GC content, and genome size differed greatly between mitochondrial and nuclear genomes. Phylogenetic analysis based on 14 concatenated mitochondrial genes predicted evolutionary relationships largely consistent with those predicted by a phylogeny constructed from 2,422 nuclear genes. Comparing similarities in interspecies patterns of codon usage bias between mitochondrial and nuclear genomes showed that species grouped differently by patterns of codon usage bias depending on whether analyses were performed using mitochondrial or nuclear relative synonymous usage values. We found that patterns of codon usage bias at gene level are more similar between mitogenomes of different species than the mitogenome and nuclear genome of the same species. Finally, we inferred that, although most genes-both nuclear and mitochondrial-deviated from the neutral expectation for codon usage, mitogenomes were not under translational selection while nuclear genomes were under moderate translational selection. These results contribute to the study of mitochondrial genome evolution in filamentous fungi.
| S-EPMC9836360 | biostudies-literature
Project description:For genetic identification of Aspergillus Section Flavi isolates and detection of intraspecific variation, we developed a novel method for heteroduplex panel analysis (HPA) utilizing fragments of the internal transcribed spacer (ITS) regions (ITS1-5.8S-ITS2) of the rRNA gene that was PCR amplified with universal primers. The method involves formation of heteroduplexes with a set of reference fragments amplified from Aspergillus flavus, A. parasiticus, A. tamarii, and A. nomius and subsequent minislab vinyl polymer gel electrophoresis. The test panel is compared with species-specific standard panels (F-1, P-1, T-1, and N-1) generated by pairwise reannealing among four reference fragments. Of 90 test panels, 89 succeeded in identifying the species and 74 were identical to one of the four standard panels. Of the 16 new panels, 11 A. flavus/A. oryzae panels were identical and typed as F-2 and 4 of 5 A. nomius panels were typed as N-2 or N-3. The other strain, A. nomius IMI 358749, was unable to identify the species because no single bands were formed with any of the four reference strains. DNA sequencing revealed that our HPA method has the highest sensitivity available and is able to detect as little as one nucleotide of diversity within the species. When Penicillium or non-Section Flavi Aspergillus was subjected to HPA, the resulting bands of heteroduplexes showed apparently lower mobility and poor heteroduplex formation. This indicates that HPA is a useful identification method without morphological observation and is suitable for rapid and inexpensive screening of large numbers of isolates. The HPA typing coincided with the taxonomy of Section Flavi and is therefore applicable as an alternative to the conventional methods (Samson, R. A., E. S. Hoekstra, J. C. Frisvad, and O. Filtenborg, p. 64-97, in Introduction to Food- and Airborne Fungi, 6th ed., 2000).
| S-EPMC93133 | biostudies-literature
Project description:For Aspergillus flavus, a pathogen of considerable economic and health concern, successful gene knockout work for more than a decade has relied nearly exclusively on using nonhomologous end-joining pathway (NHEJ)-deficient recipients via forced double-crossover recombination of homologous sequences. In this study, a simple CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR-associated nuclease) genome editing system that gave extremely high (>95%) gene-targeting frequencies in A. flavus was developed. It contained a shortened Aspergillus nidulans AMA1 autonomously replicating sequence that maintained good transformation frequencies and Aspergillus oryzae ptrA as the selection marker for pyrithiamine resistance. Expression of the codon-optimized cas9 gene was driven by the A. nidulans gpdA promoter and trpC terminator. Expression of single guide RNA (sgRNA) cassettes was controlled by the A. flavus U6 promoter and terminator. The high transformation and gene-targeting frequencies of this system made generation of A. flavus gene knockouts with or without phenotypic changes effortless. Additionally, multiple-gene knockouts of A. flavus conidial pigment genes (olgA/copT/wA or olgA/yA/wA) were quickly generated by a sequential approach. Cotransforming sgRNA vectors targeting A. flavus kojA, yA, and wA gave 52%, 40%, and 8% of single-, double-, and triple-gene knockouts, respectively. The system was readily applicable to other section Flavi aspergilli (A. parasiticus, A. oryzae, A. sojae, A. nomius, A. bombycis, and A. pseudotamarii) with comparable transformation and gene-targeting efficiencies. Moreover, it gave satisfactory gene-targeting efficiencies (>90%) in A. nidulans (section Nidulantes), A. fumigatus (section Fumigati), A. terreus (section Terrei), and A. niger (section Nigri). It likely will have a broad application in aspergilli. IMPORTANCE CRISPR/Cas9 genome editing systems have been developed for many aspergilli. Reported gene-targeting efficiencies vary greatly and are dependent on delivery methods, repair mechanisms of induced double-stranded breaks, selection markers, and genetic backgrounds of transformation recipient strains. They are also mostly strain specific or species specific. This developed system is highly efficient and allows knocking out multiple genes in A. flavus efficiently either by sequential transformation or by cotransformation of individual sgRNA vectors if desired. It is readily applicable to section Flavi species and aspergilli in other sections ("section" is a taxonomic rank between genus and species). This cross-Aspergillus section system is for wild-type isolates and does not require homologous donor DNAs to be added, NHEJ-deficient strains to be created, or forced recycling of knockout recipients to be performed for multiple-gene targeting. Hence, it simplifies and expedites the gene-targeting process significantly.
| S-EPMC9927283 | biostudies-literature