Aspergillus section Nidulantes (formerly Emericella): Polyphasic taxonomy, chemistry and biology

Abstract

Aspergillus section Nidulantes includes species with striking morphological characters, such as biseriate conidiophores with brown-pigmented stipes, and if present, the production of ascomata embedded in masses of Hülle cells with often reddish brown ascospores. The majority of species in this section have a sexual state, which were named Emericella in the dual name nomenclature system. In the present study, strains belonging to subgenus Nidulantes were subjected to multilocus molecular phylogenetic analyses using internal transcribed spacer region (ITS), partial β-tubulin (BenA), calmodulin (CaM) and RNA polymerase II second largest subunit (RPB2) sequences. Nine sections are accepted in subgenus Nidulantes including the new section Cavernicolus. A polyphasic approach using morphological characters, extrolites, physiological characters and phylogeny was applied to investigate the taxonomy of section Nidulantes. Based on this approach, section Nidulantes is subdivided in seven clades and 65 species, and 10 species are described here as new. Morphological characters including colour, shape, size, and ornamentation of ascospores, shape and size of conidia and vesicles, growth temperatures are important for identifying species. Many species of section Nidulantes produce the carcinogenic mycotoxin sterigmatocystin. The most important mycotoxins in Aspergillus section Nidulantes are aflatoxins, sterigmatocystin, emestrin, fumitremorgins, asteltoxins, and paxillin while other extrolites are useful drugs or drug lead candidates such as echinocandins, mulundocandins, calbistrins, varitriols, variecolins and terrain. Aflatoxin B1 is produced by four species: A. astellatus, A. miraensis, A. olivicola, and A. venezuelensis.

Structural and stereochemical diversity in prenylated indole alkaloids containing the bicyclo[2.2.2]diazaoctane ring system from marine and terrestrial fungi

“…116 Finally, Aspergillus subgenus Nidulantes section Versicolores contains producers of “Aspergamides”: A. amoenus and A. protuberus , 35 but “Aspergamides” could not be found in any species in section Nidulantes . 130 Further studies will show whether the producing species in these sections of Aspergilli all have stereochemical diversity in their production of these compounds.…”

Cryptic Aspergillus from clinical samples in the USA and description of a new species in section Flavipedes

“…On the other hand, A. pachycristatus is the only species of the section Nidulantes identified here that has not been reported from clinical samples before. This species was described from Chinese soil, and morphologically also resembles A. nidulans , but the ascospores of A. pachycristatus show thicker crests . The closest related species to A. pachycristatus is A. rugulosus ; however, the latter can be distinguished by the rugulose ornamentation on the convex surface of ascospores; in A. pachycristatus , the ascospore surface is smooth …”

“…Another difficulty in identifying cryptic species is the fact that the taxonomy is being continuously updated with new modifications due to the new criteria for fungal nomenclature, synonymisations and new species being constantly described in the current literature . For example, among the species reported in the isolates of this study, three of them ( A. europaeus , A. micronesiensis and A. spelaeus ) were not even described at the moment of their isolation from clinical samples.…”

“…Aspergillus unguis has been reported as causal agent of several cases of onychomycosis, and it has also been associated with cases of asthma in children . This latter species is also morphologically similar to A. nidulans, but they can be differentiated by the ability to grow at 40°C; while A. nidulans grows profusely, reaching 46 mm in 5 days, A. unguis is unable to grow at this temperature . On the other hand, A. pachycristatus is the only species of the section Nidulantes identified here that has not been reported from clinical samples before.…”

Polyphasic taxonomy ofAspergillussectionCervini

“…Based on morphological similarities Samson (1979) proposed that A. bisporus described by Kwon-Chung & Fennell (1971) also belongs to section Cervini . However, molecular studies revealed that A. bisporus is distantly related to this section, and belongs to subgenus Nidulantes , section Bispori (Peterson 2000, Peterson, 2008, Peterson et al., 2008, Chen et al., 2016). Udagawa et al.…”