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Identification of fungi of the genus Aspergillus section nigri using polyphasic taxonomy.

ABSTRACT: In spite of the taxonomy of the Aspergillus species of the Nigri Section being regarded as troublesome, a number of methods have been proposed to aid in the classification of this Section. This work aimed to distinguish Aspergillus species of the Nigri Section from foods, grains and caves on the basis in Polyphasic Taxonomy by utilizing morphologic and physiologic characters, and sequencing of ß-tubulin and calmodulin genes. The morphologic identification proved useful for some species, such as A. carbonarius and Aspergillus sp UFLA DCA 01, despite not having been totally effective in elucidating species related to A. niger. The isolation of the species of the Nigri Section on Creatine Sucrose Agar (CREA) enabled to distinguish the Aspergillus sp species, which was characterized by the lack of sporulation and by the production of sclerotia. Scanning Electron microscopy (SEM) allowed distinguishing the species into two distinct groups. The production of Ochratoxin A (OTA) was only found in the A. carbonarius and A. niger species. The sequencing of ?-tubulin gene was efficient in differing most of the Aspergillus species from the Nigri Section with the exception of Aspergillus UFLA DCA 01, which could not be distinguished from A. costaricaensis. This species is morphologically similar to A. costaricaencis for its low sporulation capacity and high sclerotia production, but it differs morphologically from A. costaricaensis for its conidial ornamentation and size of vesicles. Equally, based on partial calmodulin gene sequence data Aspergillus UFLA DCA 01 differs from A. costaricaensis.

SUBMITTER: Silva DM

PROVIDER: S-EPMC3769849 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature

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Identification of fungi of the genus Aspergillus section nigri using polyphasic taxonomy.

Silva Daiani M DM Batista Luís R LR Rezende Elisângela F EF Fungaro Maria Helena P MH Sartori Daniele D Alves Eduardo E

Brazilian journal of microbiology : [publication of the Brazilian Society for Microbiology] 20110401 2

In spite of the taxonomy of the Aspergillus species of the Nigri Section being regarded as troublesome, a number of methods have been proposed to aid in the classification of this Section. This work aimed to distinguish Aspergillus species of the Nigri Section from foods, grains and caves on the basis in Polyphasic Taxonomy by utilizing morphologic and physiologic characters, and sequencing of ß-tubulin and calmodulin genes. The morphologic identification proved useful for some species, such as ...[more]

PMID: 24031691

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Project description:Aspergillus section Candidi historically included a single white-spored species, A. candidus. Later studies clarified that other species may also belong to this section. In this study, we examined isolates of species tentatively assigned to section Candidi using a polyphasic approach. The characters examined include sequence analysis of partial beta-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 Candidi includes 4 species: A. candidus, A. campestris, A. taichungensis and A. tritici. This is strongly supported by all the morphological characteristics that are characteristic of section Candidi: slow growing colonies with globose conidial heads having white to yellowish conidia, conidiophores smooth, small conidiophores common, metulae present and covering the entire vesicle, some large Aspergillus heads with large metulae, presence of diminutive heads in all species, conidia smooth or nearly so with a subglobose to ovoid shape, and the presence of sclerotia in three species (A. candidus, A. taichungensis and A. tritici). Aspergillus tritici has been suggested to be the synonym of A. candidus previously, however, sequence data indicate that this is a valid species and includes isolates came from soil, wheat grain, flour and drums from India, Ghana, Sweden, The Netherlands and Hungary, making it a relatively widespread species. All species produce terphenyllins and candidusins and three species (A. candidus, A. campestris and A. tritici) produce chlorflavonins. Xanthoascins have only been found in A. candidus. Each of the species in section Candidi produce several other species specific extrolites, and none of these have been found in any other Aspergillus species. A. candidus has often been listed as a human pathogenic species, but this is unlikely as this species cannot grow at 37 degrees C. The pathogenic species may be A. tritici or white mutants of Aspergillus flavus.

Project description:Four new species, Aspergillus eucalypticola, A. neoniger, A. fijiensis and A. indologenus are described and illustrated. Aspergillus eucalypticola was isolated from Eucalyptus leaf from Australia, and is related to A. tubingensis and A. costaricaensis, but could clearly be distinguished from them based on either ?-tubulin or calmodulin sequence data. Aspergillus eucalypticola produced pyranonigrin A, funalenone, aurasperone B and other naphtho-?-pyrones. Aspergillus neoniger is also a biseriate species isolated from desert sand in Namibia, and mangrove water in Venezuela, which produces aurasperone B and pyranonigrin A. Aspergillus fijiensis is a uniseriate species related to A. aculeatinus, and was isolated from soil in Fiji, and from Lactuca sativa in Indonesia. This species is able to grow at 37 °C, and produces asperparalines and okaramins. Aspergillus indologenus was isolated from soil, India. This species also belongs to the uniseriate group of black aspergilli, and was found to be related to, but clearly distinguishable from A. uvarum based on ?-tubulin, calmodulin and ITS sequence data. Aspergillus indologenus produced the insecticidal compounds okaramins A, B, H, and two types of indol-alkaloids which have not been structure elucidated. Two other species, A. violaceofuscus and A. acidus, are revalidated based on molecular and extrolite data. Aspergillus violaceofuscus was found to be related to A. japonicus, and produced some of the same interesting indol-alkaloids as A. indologenus, and also produced several families of partially characterised extrolites that were also found in A. heteromorphus. Aspergillus acidus (previously known as A. foetidus var. pallidus and A. foetidus var. acidus) is also a valid species, while A. foetidus is a synonym of A. niger based on molecular and physiological data. Two other species described previously, A. coreanus and A. lacticoffeatus, were found to be colour mutants of A. acidus and A. niger, respectively. Methods which could be used to distinguish the two closely related and economically important species A. niger and A. awamori are also detailed. Although these species differ in their occurrence and several physiological means (elastase activities, abilities to utilise 2-deoxy-D-glucose as sole carbon source), our data indicate that only molecular approaches including sequence analysis of calmodulin or ?-tubulin genes, AFLP analysis, UP-PCR analysis or mtDNA RFLP analysis can be used reliably to distinguish these sibling species. Aspergillus section Nigri now includes 26 taxa.

Dataset Information

Identification of fungi of the genus Aspergillus section nigri using polyphasic taxonomy.

Publications

Identification of fungi of the genus Aspergillus section nigri using polyphasic taxonomy.

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