Chemotaxonomy and Morphology of Aspergillus Fumigatus and Related Taxa

Frisvad, Jens Christian; Samson, Robert A.

doi:10.1007/978-1-4899-3579-3_17

Cited by 44 publications

(28 citation statements)

References 32 publications

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“…A previous recommendation to elevate A. fumigatus var. ellipticus to the species A. neoellipticus based on mitospore ornamentation (Kozakiewicz 1989) was not followed by Frisvad and Samson (Frisvad and Samson 1990) for similar reasons; only one individual of A. fumigatus var. ellipticus was shown to have the unusual ornamentation and the spore morphology of A. fumigatus sensu stricto were found to be extremely variable.…”

Section: Cryptic Speciesmentioning

confidence: 99%

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Cryptic Speciation in the Cosmopolitan and Clonal Human Pathogenic Fungus Aspergillus Fumigatus

et al. 2005

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Abstract. Microbes and other organisms smaller than one to a few millimeters in size are hypothesized to have global populations, in contrast to the geographically restricted ranges of larger organisms. However, fungi, which routinely have reproductive propagules no larger than 10 micrometers, challenge the generality of this hypothesis because recent studies have shown that globally distributed morphological species embrace two or more geographically restricted phylogenetic species. We used the concordance of gene genealogies to recognize phylogenetic species in the globally distributed opportunistic human pathogenic fungus, Aspergillus fumigatus. Based on DNA sequence data of five loci for each of 63 individuals collected from five continents, we have delineated two phylogenetic species in this single morphological species. Unlike all other fungi examined to date, both genetically isolated groups showed a global distribution with no evidence of a correlation between genotype and geographic location. Sexual reproduction has never been observed in A. fumigatus, but when the same data were used to explore the association of alleles at the five loci for one of the phylogenetic species, evidence was found to support recombination. The discovery of a cryptic species is medically relevant because different species are likely to differ in virulence or drug resistance. The discovery of a globally distributed A. fumigatus species clade highlights the need for ecological studies of the fungus to either document global dispersal or propose alternative mechanisms by which it persists as single, global phylogenetic population.

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Section: Cryptic Speciesmentioning

confidence: 99%

“…ellipticus was shown to have the unusual ornamentation and the spore morphology of A. fumigatus sensu stricto were found to be extremely variable. Moreover, Frisvad and Samson (1990) reported that individuals labeled as A. fumigatus var. fumigatus or A. fumigatus var.…”

Section: Cryptic Speciesmentioning

confidence: 99%

Cryptic Speciation in the Cosmopolitan and Clonal Human Pathogenic Fungus Aspergillus Fumigatus

et al. 2005

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“…Aspergillus fumigatus and Neosartorya fischeri are two closely related euascomycete molds (Eurotiomycetes, Pezizomycotina) in the genus Aspergillus, subgenus Fumigati, section Fumigati (12,33,36,42). A. fumigatus is the most common cause of invasive aspergillosis infection in humans (8,22) and is only known to reproduce by asexual means involving the production of masses of mitotic conidiospores.…”

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DNA Sequence Characterization and Molecular Evolution of MAT1 and MAT2 Mating-Type Loci of the Self-Compatible Ascomycete Mold Neosartorya fischeri

2007

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Degenerate PCR and chromosome-walking approaches were used to identify mating-type (MAT) genes and flanking regions from the homothallic (sexually self-fertile) euascomycete fungus Neosartorya fischeri, a close relative of the opportunistic human pathogen Aspergillus fumigatus. Both putative alpha-and high-mobilitygroup-domain MAT genes were found within the same genome, providing a functional explanation for selffertility. However, unlike those in many homothallic euascomycetes (Pezizomycotina), the genes were not found adjacent to each other and were termed MAT1 and MAT2 to recognize the presence of distinct loci. Complete copies of putative APN1 (DNA lyase) and SLA2 (cytoskeleton assembly control) genes were found bordering the MAT1 locus. Partial copies of APN1 and SLA2 were also found bordering the MAT2 locus, but these copies bore the genetic hallmarks of pseudogenes. Genome comparisons revealed synteny over at least 23,300 bp between the N. fischeri MAT1 region and the A. fumigatus MAT locus region, but no such long-range conservation in the N. fischeri MAT2 region was evident. The sequence upstream of MAT2 contained numerous candidate transposase genes. These results demonstrate a novel means involving the segmental translocation of a chromosomal region by which the ability to undergo self-fertilization may be acquired. The results are also discussed in relation to their significance in indicating that heterothallism may be ancestral within the Aspergillus section Fumigati.

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“…Members of the Aspergillus section Fumigati are distinguished by the profiles of mycotoxins and secondary metabolites that they produce (2) and, in the case of species with known sexual states (genus Neosartorya), the morphology of the ascospores (17). The evolutionary relationship of A. fumigatus to other species from Aspergillus section Fumigati has been investigated using DNA sequence data obtained from the ␤-tubulin gene (3), the hydrophobin gene (3), and the mitochondrial cytochrome b gene (21).…”

mentioning

confidence: 99%

“…The evolutionary relationship of A. fumigatus to other species from Aspergillus section Fumigati has been investigated using DNA sequence data obtained from the ␤-tubulin gene (3), the hydrophobin gene (3), and the mitochondrial cytochrome b gene (21). These analyses have shown that morphological variation in isolates of A. fumigatus is not necessarily accompanied by variation in chemical profiles or DNA sequences (2,21).…”

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Multiple Genetically Distinct Groups Revealed among Clinical Isolates Identified as Atypical Aspergillus fumigatus

et al. 2005

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To investigate whether genetic variants of A. fumigatus are found among clinical isolates, four isolates that were originally identified as poorly sporulating strains of Aspergillus fumigatus were subjected to molecular analysis. DNA sequence analysis of the alkaline protease genes of these isolates showed that each is genetically distinct and each shows substantial variation (7 to 11%) from the A. fumigatus nucleotide sequence. Subsequent morphological examination suggested that all of the isolates could be classified as Aspergillus viridinutans. To clarify the taxonomic status of these four clinical isolates and of two previously identified as atypical A. fumigatus isolates, partial ␤-tubulin and 18S rRNA gene sequences were determined. Each of the six atypical strains had a unique ␤-tubulin sequence, whereas the sequences of three standard isolates of A. fumigatus, which were included as controls, were identical to the published A. fumigatus ␤-tubulin sequence. The very low level of DNA sequence variation detected in standard isolates of A. fumigatus compared with other isolates from members of Aspergillus section Fumigati suggests that it may be a relatively recently evolved species. The 18S rRNA gene of two of the atypical isolates differed from that of A. fumigatus at a single nucleotide position. Phylogenetic analyses do not support the classification of all of these isolates as A. viridinutans. Thus, some of these isolates represent new species which are potential opportunistic pathogens.Aspergillus fumigatus is the species most commonly associated with aspergillosis in immunocompromised patients. A number of DNA-based methods have been developed to detect A. fumigatus for diagnostic purposes and to type strains to study the origin and transmission of nosocomial infections. Diagnostic methods using PCR rely on amplification of specific DNA sequences, which could vary between strains. Sequence analysis of protein coding genes such as the cytochrome b gene (21) has revealed little or no sequence variation between standard isolates of A. fumigatus. In contrast, seven isolates of Aspergillus viridinutans, another asexual species in the section Fumigati, showed considerable genetic variability in ␤-tubulin gene sequences (19).Members of the Aspergillus section Fumigati are distinguished by the profiles of mycotoxins and secondary metabolites that they produce (2) and, in the case of species with known sexual states (genus Neosartorya), the morphology of the ascospores (17). The evolutionary relationship of A. fumigatus to other species from Aspergillus section Fumigati has been investigated using DNA sequence data obtained from the ␤-tubulin gene (3), the hydrophobin gene (3), and the mitochondrial cytochrome b gene (21). These analyses have shown that morphological variation in isolates of A. fumigatus is not necessarily accompanied by variation in chemical profiles or DNA sequences (2, 21).In a previous study, DNA sequence analysis of the alkaline protease gene (Alp) was used to investigate two atypical iso...

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Chemotaxonomy and Morphology of Aspergillus Fumigatus and Related Taxa

Abstract: SUMMARY

Cited by 44 publications

References 32 publications

Cryptic Speciation in the Cosmopolitan and Clonal Human Pathogenic Fungus Aspergillus Fumigatus

Cryptic Speciation in the Cosmopolitan and Clonal Human Pathogenic Fungus Aspergillus Fumigatus

DNA Sequence Characterization and Molecular Evolution of MAT1 and MAT2 Mating-Type Loci of the Self-Compatible Ascomycete Mold Neosartorya fischeri

Multiple Genetically Distinct Groups Revealed among Clinical Isolates Identified as Atypical Aspergillus fumigatus

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