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Taxonomic Characterization and Secondary Metabolite Profiling of Aspergillus Section Aspergillus Contaminating Feeds and Feedstuffs.

Greco M, Kemppainen M, Pose G, Pardo A - Toxins (Basel) (2015)

Bottom Line: All the isolates produced neoechinulin A, 17 isolates were positive for cladosporin and echinulin, and 18 were positive for neoechinulin B.Physcion and preechinulin were detected in a minor proportion of the isolates.This is the first report describing the detailed species composition and the secondary metabolite profiles of Aspergillus section Aspergillus contaminating animal feeds.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Micología Molecular, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Bernal 1876, Argentina. mariana.greco@gmail.com.

ABSTRACT
Xerophilic fungal species of the genus Aspergillus are economically highly relevant due to their ability to grow on low water activity substrates causing spoilage of stored goods and animal feeds. These fungi can synthesize a variety of secondary metabolites, many of which show animal toxicity, creating a health risk for food production animals and to humans as final consumers, respectively. Animal feeds used for rabbit, chinchilla and rainbow trout production in Argentina were analysed for the presence of xerophilic Aspergillus section Aspergillus species. High isolation frequencies (>60%) were detected in all the studied rabbit and chinchilla feeds, while the rainbow trout feeds showed lower fungal charge (25%). These section Aspergillus contaminations comprised predominantly five taxa. Twenty isolates were subjected to taxonomic characterization using both ascospore SEM micromorphology and two independent DNA loci sequencing. The secondary metabolite profiles of the isolates were determined qualitatively by HPLC-MS. All the isolates produced neoechinulin A, 17 isolates were positive for cladosporin and echinulin, and 18 were positive for neoechinulin B. Physcion and preechinulin were detected in a minor proportion of the isolates. This is the first report describing the detailed species composition and the secondary metabolite profiles of Aspergillus section Aspergillus contaminating animal feeds.

No MeSH data available.


Related in: MedlinePlus

Scanning electron microscopy photos of ascospores of A. montevidensis (A, 1–3); A. chevalieri (B, 1–3); A. pseudoglaucus (C, 1–3); A. ruber (D, 1–3) and A. proliferans (E, 1–3). Scale bars: A(1–3)-B(2,3)-C(1–3)-D(1–3)-E(1,3) = 1 µm; B1, E2 = 2 µm.
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toxins-07-03512-f001: Scanning electron microscopy photos of ascospores of A. montevidensis (A, 1–3); A. chevalieri (B, 1–3); A. pseudoglaucus (C, 1–3); A. ruber (D, 1–3) and A. proliferans (E, 1–3). Scale bars: A(1–3)-B(2,3)-C(1–3)-D(1–3)-E(1,3) = 1 µm; B1, E2 = 2 µm.

Mentions: Scanning electron microscopy (SEM) has traditionally been used as a tool for species classification in the section Aspergillus. Especially ascospore size, surface ornamentation and features of the equatorial region have offered characteristics of taxonomic value for species differentiation. To further confirm the species identity of the selected isolates, their ascospore micromorphology was analysed by SEM. The results were concordant with the growth morphological species identification and confirmed the isolates as representatives of the respective four Aspergillus section Aspergillus species. The ascospore characteristics did not significantly differ from those already described [8,47]. A set of representative SEM photos are shown in Figure 1 and a summary of the ascospores characteristics is presented in Table 3. Two isolates, originally identified based on the growth characters and light microcopy observation of the ascospores as A. montevidensis, were re-identified as A. chevalieri by SEM. In addition, one isolate originally considered as A. chevalieri was re-identified as A. ruber. These changes in the isolate species identity were further supported by DNA analyses (see below) and demonstrates the value of SEM as a complementary tool for species identification in the section Aspergillus. It is however noteworthy that the ascospores of A. proliferans and A. ruber have highly similar size and micromorphology and therefore SEM does not offer solid separation of these two species. Moreover, some strains of A. ruber are reported to show atypical ascospore morphology making spore size and surface ornamentation very weak identification characteristics for A. ruber and A. proliferans [42]. Our SEM study resulted in detection of slightly bigger and smoother surfaced ascospores in the case of the studied A. proliferans isolate; otherwise, the general morphological characteristics and the size of the ascopores between A. proliferans and A. ruber were highly similar. These results confirm the weak taxonomic resolution of SEM in separating A. ruber from A. proliferans, a goal that, besides some growth characteristics, can solidly be reached by DNA analyses.


Taxonomic Characterization and Secondary Metabolite Profiling of Aspergillus Section Aspergillus Contaminating Feeds and Feedstuffs.

Greco M, Kemppainen M, Pose G, Pardo A - Toxins (Basel) (2015)

Scanning electron microscopy photos of ascospores of A. montevidensis (A, 1–3); A. chevalieri (B, 1–3); A. pseudoglaucus (C, 1–3); A. ruber (D, 1–3) and A. proliferans (E, 1–3). Scale bars: A(1–3)-B(2,3)-C(1–3)-D(1–3)-E(1,3) = 1 µm; B1, E2 = 2 µm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4591650&req=5

toxins-07-03512-f001: Scanning electron microscopy photos of ascospores of A. montevidensis (A, 1–3); A. chevalieri (B, 1–3); A. pseudoglaucus (C, 1–3); A. ruber (D, 1–3) and A. proliferans (E, 1–3). Scale bars: A(1–3)-B(2,3)-C(1–3)-D(1–3)-E(1,3) = 1 µm; B1, E2 = 2 µm.
Mentions: Scanning electron microscopy (SEM) has traditionally been used as a tool for species classification in the section Aspergillus. Especially ascospore size, surface ornamentation and features of the equatorial region have offered characteristics of taxonomic value for species differentiation. To further confirm the species identity of the selected isolates, their ascospore micromorphology was analysed by SEM. The results were concordant with the growth morphological species identification and confirmed the isolates as representatives of the respective four Aspergillus section Aspergillus species. The ascospore characteristics did not significantly differ from those already described [8,47]. A set of representative SEM photos are shown in Figure 1 and a summary of the ascospores characteristics is presented in Table 3. Two isolates, originally identified based on the growth characters and light microcopy observation of the ascospores as A. montevidensis, were re-identified as A. chevalieri by SEM. In addition, one isolate originally considered as A. chevalieri was re-identified as A. ruber. These changes in the isolate species identity were further supported by DNA analyses (see below) and demonstrates the value of SEM as a complementary tool for species identification in the section Aspergillus. It is however noteworthy that the ascospores of A. proliferans and A. ruber have highly similar size and micromorphology and therefore SEM does not offer solid separation of these two species. Moreover, some strains of A. ruber are reported to show atypical ascospore morphology making spore size and surface ornamentation very weak identification characteristics for A. ruber and A. proliferans [42]. Our SEM study resulted in detection of slightly bigger and smoother surfaced ascospores in the case of the studied A. proliferans isolate; otherwise, the general morphological characteristics and the size of the ascopores between A. proliferans and A. ruber were highly similar. These results confirm the weak taxonomic resolution of SEM in separating A. ruber from A. proliferans, a goal that, besides some growth characteristics, can solidly be reached by DNA analyses.

Bottom Line: All the isolates produced neoechinulin A, 17 isolates were positive for cladosporin and echinulin, and 18 were positive for neoechinulin B.Physcion and preechinulin were detected in a minor proportion of the isolates.This is the first report describing the detailed species composition and the secondary metabolite profiles of Aspergillus section Aspergillus contaminating animal feeds.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Micología Molecular, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Bernal 1876, Argentina. mariana.greco@gmail.com.

ABSTRACT
Xerophilic fungal species of the genus Aspergillus are economically highly relevant due to their ability to grow on low water activity substrates causing spoilage of stored goods and animal feeds. These fungi can synthesize a variety of secondary metabolites, many of which show animal toxicity, creating a health risk for food production animals and to humans as final consumers, respectively. Animal feeds used for rabbit, chinchilla and rainbow trout production in Argentina were analysed for the presence of xerophilic Aspergillus section Aspergillus species. High isolation frequencies (>60%) were detected in all the studied rabbit and chinchilla feeds, while the rainbow trout feeds showed lower fungal charge (25%). These section Aspergillus contaminations comprised predominantly five taxa. Twenty isolates were subjected to taxonomic characterization using both ascospore SEM micromorphology and two independent DNA loci sequencing. The secondary metabolite profiles of the isolates were determined qualitatively by HPLC-MS. All the isolates produced neoechinulin A, 17 isolates were positive for cladosporin and echinulin, and 18 were positive for neoechinulin B. Physcion and preechinulin were detected in a minor proportion of the isolates. This is the first report describing the detailed species composition and the secondary metabolite profiles of Aspergillus section Aspergillus contaminating animal feeds.

No MeSH data available.


Related in: MedlinePlus