Corresponding author: Cobus M. Visagie ( email@example.com )
Academic editor: Cecile Gueidan
© 2017 Cobus M. Visagie, Neriman Yilmaz, Justin B. Renaud, Mark W. Sumarah, Vit Hubka, Jens C. Frisvad, Amanda J. Chen, Martin Meijer, Keith A. Seifert.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Visagie CM, Yilmaz N, Renaud JB, Sumarah MW, Hubka V, Frisvad JC, Chen AJ, Meijer M, Seifert KA (2017) A survey of xerophilic Aspergillus from indoor environment, including descriptions of two new section Aspergillus species producing eurotium-like sexual states. MycoKeys 19: 1-30. https://doi.org/10.3897/mycokeys.19.11161
Xerophilic fungi grow at low water activity or low equilibrium relative humidity and are an important part of the indoor fungal community, of which Aspergillus is one of the dominant genera. A survey of xerophilic fungi isolated from Canadian and Hawaiian house dust resulted in the isolation of 1039 strains; 296 strains belong to Aspergillus and represented 37 species. Reference sequences were generated for all species and deposited in GenBank. Aspergillus sect. Aspergillus (formerly called Eurotium) was one of the most predominant groups from house dust with nine species identified. Additional cultures deposited as Eurotium were received from the Canadian Collection of Fungal Cultures and were also re-identified during this study. Among all strains, two species were found to be new and are introduced here as A. mallochii and A. megasporus. Phylogenetic comparisons with other species of section Aspergillus were made using sequences of ITS, β-tubulin, calmodulin and RNA polymerase II second largest subunit. Morphological observations were made from cultures grown under standardized conditions. Aspergillus mallochii does not grow at 37 °C and produces roughened ascospores with incomplete equatorial furrows. Aspergillus megasporus produces large conidia (up to 12 µm diam) and roughened ascospores with equatorial furrows. Echinulin, quinolactacin A1 & A2, preechinulin and neoechinulin A & B were detected as major extrolites of A. megasporus, while neoechinulin A & B and isoechinulin A, B & C were the major extrolites from A. mallochii.
BenA, CaM, indoor environments, mycotoxin, RPB2
Species of Aspergillus section Aspergillus, the “A. glaucus” group of
Xerophily is a common physiological property of many Aspergillus species from several subgenera and sections, enabling those species to grow at low water activity (aw) or equilibrium relative humidity (ERH) (
Species of section Aspergillus produce many extrolites exhibiting a wide range of biological activities (
Xerophilic fungi are well studied from a morphological point of view, but much work remains to develop reference sequence data for them. In this paper, we report on the diversity of Aspergillus isolated from house dust using media with low aw that select for the growth of xerophiles. Reference sequences are released for all species, including those received as Eurotium from the Canadian Collection of Fungal Cultures and re-identified here. Furthermore, we describe two new species and report on their extrolite production.
House dust samples were received from various areas in North America. A modified dilution-to-extinction method (
In addition to newly obtained house dust isolates, several strains, including unidentified isolates and some reference or ex-type cultures, of Aspergillus sect. Aspergillus were obtained from the Canadian Collection of Fungal Cultures, Canada (DAOMC) and the CBS-KNAW Fungal Biodiversity Centre, the Netherlands (CBS).
Colony characters were recorded from cultures grown for 7 d on various media, including CYA (Czapek yeast autolysate agar), MEA (Blakeslee’s malt extract agar), CREA (Creatine sucrose agar), CY20S (CYA with 20% sucrose agar), MEA20S (MEA with 20% sucrose agar), DG18, YES (yeast extract sucrose agar), M40Y (Harrold’s agar; 2% malt, 0.5% yeast extract, 40% sucrose), MY50G and MY10-12 (
DNA was extracted from 8–10 d old colonies grown on DG18 using the UltracleanTM Microbial DNA isolation Kit (MoBio Laboratories Inc., Solana Beach, USA). Loci chosen for amplification included ITS barcodes (internal transcribed spacer rDNA region, including ITS1-5.8S-ITS2) (
As a preliminary step in identification, CaM sequences derived from the newly isolated cultures were compared to an ex-type reference sequence database published by
MP analyses were run in PAUP* v. 4.0b10 (
BI analyses were run in MrBayes v. 3.2.5 (
For extrolite analysis, all strains were grown on 9 cm polystyrene Petri dishes on MEA supplemented with 7.5% NaCl at 25 °C for 14 d. Six agar plugs from each fungal isolate were removed with a sterilized 7 mm cork borer and placed into a 13 mL polypropylene tube. Ethyl acetate (2 mL) was added to the tubes and vortexed for 30 s, followed by 1 h of sonication at 30 °C and vortexed again for 30 s. The supernatants were transferred into clean polypropylene tubes and dried on a centrifugal vacuum concentrator at 35 °C. Extracts were reconstituted in 1 mL of 8:2 methanol:water and filtered into 2 mL amber glass HPLC vials using a 0.45 µm PVDF syringe filter. Extracts were immediately stored at -20 °C until LC-MS analysis. Extracts were analyzed on a Q-Exactive orbitrap coupled to a 1290 Agilent HPLC in both positive and negative polarities. Chemical formula of observed extrolites were determined with Xcalibur® software using accurate mass measurements and manually verified by isotopic pattern. Chemical formulae were searched against AntiBase2013 and Scifinder and putatively confirmed by comparing product ions observed with those published in the literature or though manual interpretation. The fungi were also analysed using the HPLC-DAD method described by
Isolations from house dust collected in Canada and Hawaii resulted in 1039 isolates of xerophilic/xerotolerant fungi. 296 isolates were identified as Aspergillus, of which members from sections Aspergillus, Nidulantes (A. versicolor clade) and Restricti were most abundant. Strains were identified to species using CaM sequences and identities confirmed by morphological examination. They include A. chevalieri, A. cibarius, A. montevidensis, A. proliferans, A. pseudoglaucus, A. ruber and A. tonophilus from sect. Aspergillus. In section Nidulantes (A. versicolor clade), A. jensenii and A. sydowii were isolated most frequently, while A. creber, A. fructus, A. protuberus, A. tenneseensis and A. versicolor were also recovered. A large degree of sequence diversity was observed in sect. Restricti and will be presented in a separate study. Other Aspergillus species identified include A. aureolatus, A. candidus, A. calidoustus, A. flavus, A. japonicus, A. lentulus, A. luchuensis, A. micronesiensis, A. niger, A. pragensis, A. tamarii, A. terreus, A. tubingensis, A. welwitschiae and A. westerdijkiae. Reference sequences, mostly CaM, obtained for these species were uploaded to GenBank under accession numbers KX894565–KX894666 and KY351765–KY351785, and are included in Suppl. material
To demonstrate genealogical concordance for the two new species, phylogenies for all known species of sect. Aspergillus were prepared (Table
One of the most parsimonious trees of Aspergillus sect. Aspergillus based on ITS, CaM, BenA and RPB2. Trees were rooted to A. xerophilus, A. leucocarpus and A. osmophilus. Support in nodes higher than 80% bootstrap values and 0.95 posterior probabilities are shown above thickened branches. New species are shown in bold and colour, while ex-type strains are followed by T.
One of the most parsimonious trees of Aspergillus sect. Aspergillus based on a combined dataset of ITS, BenA, CaM and RPB2. The tree was rooted to A. xerophilus, A. leucocarpus and A. osmophilus. Support in nodes higher than 80% bootstrap values and 0.95 posterior probabilities are shown above thickened branches. New species are shown in bold and colour, while ex-type strains are followed by T.
Strains used for phylogenetic analyses.
|Species||Strains||Origin||GenBank accession numbers|
|Aspergillus appendiculatus||CBS 374.75T; DAOMC 231665; IMI 278374; ETH 8286||Smoked sausage, Switserland||HE615132||HE801318||HE801333||HE801307|
|Aspergillus appendiculatus||CBS101746; AS 3.4673||Sheep dung, China||HE615133||HE801319||HE801334||HE801308|
|Aspergillus brunneus||CBS 112.26T; NRRL131; ATCC 1021; IMI 211378; MUCL 15646||Fig, USA||EF652060||EF651998||EF651907||EF651939|
|Aspergillus brunneus||CBS 113.27; NRRL124; ATCC 1036; IMI 029188||Unknown||EF652056||EF651997||EF651904||EF651938|
|Aspergillus brunneus||NRRL 133||Unknown||EF652061||EF651999||EF651908||EF651940|
|Aspergillus chevalieri||CBS 522.65T; NRRL 78; ATCC 16443; IMI 211382||Coffee beans, USA||EF652068||EF652002||EF651911||EF651954|
|Aspergillus chevalieri||NRRL 4755||Contaminated culture, USA||EF652071||EF652004||EF651913||EF651956|
|Aspergillus chevalieri||NRRL 79||Unknown, USA||EF652069||EF652003||EF651912||EF651955|
|Aspergillus cibarius||KACC 46346T||Meju, Korea||JQ918177||JQ918183||JQ918180||JQ918186|
|Aspergillus cibarius||KACC 46764||Meju, Korea||JQ918178||JQ918184||JQ918181||JQ918187|
|Aspergillus cibarius||KACC 46765||Meju, Korea||JQ918179||JQ918185||JQ918182||JQ918188|
|Aspergillus costiformis||CBS 101749T; AS 3.4664||Rotten paper, China||HE615136||HE801320||HE801338||HE801309|
|Aspergillus cristatus||CBS 123.53T; NRRL 4222; ATCC 16468; IMI 172280; MUCL 15644||Unknown, South Africa||EF652078||EF652001||EF651914||EF651957|
|Aspergillus cumulatus||KACC 47316T||Rice straw, Korea||KF928303||KF928300||KF928297||KF928294|
|Aspergillus cumulatus||KACC 47513||Indoor air from meju fermentation room, Korea||KF928304||KF928301||KF928298||KF928295|
|Aspergillus cumulatus||KACC 47514||Indoor air from meju fermentation room, Korea||KF928305||KF928302||KF928299||KF928296|
|Aspergillus glaucus||CBS 516.65T; NRRL 116; ATCC 16469; IMI 211383||Unpainted basement board, USA||EF652052||EF651989||EF651887||EF651934|
|Aspergillus glaucus||NRRL 117; ATCC 66470||Unpainted basement board, USA||EF652053||EF651990||EF651888||EF651935|
|Aspergillus glaucus||NRRL 120; ATCC 16925; FRR 120||Unknown||EF652054||EF651991||EF651889||EF651936|
|Aspergillus glaucus||NRRL 121; IMI 313756||Unknown||EF652055||EF651992||EF651890||EF651937|
|Aspergillus intermedius||CBS 377.75; IMI 278376; ETH 8277||Soil, Spain||HE974459||HE974437||HE974432||HE974425|
|Aspergillus intermedius||CBS 523.65T; NRRL 82; ATCC 16444; IMI 089278; IMI 089278ii; DSM 2830||Unknown, United Kingdom||EF652074||EF652012||EF651892||EF651958|
|Aspergillus intermedius||NRRL 4817; IMI 313754||Unknown||EF652072||EF652014||EF651894||EF651960|
|Aspergillus intermedius||NRRL 84||Unknown||EF652070||EF652013||EF651893||EF651959|
|Aspergillus leucocarpus||CBS 353.68T; NRRL3497; IMI 278375||Raw sausage, Germany||EF652087||EF652023||EF651925||EF651972|
|Aspergillus mallochii||DAOMC 146054T = CBS 141928 = DTO 357A5 = KAS 7618||Pack rat dung, USA||KX450907||KX450902||KX450889||KX450894|
|Aspergillus mallochii||CBS 141776 = DTO 343G3||'Chocolat miroir' icing for cake, the Netherlands||KX450908||KX450903||KX450890||KX450895|
|Aspergillus megasporus||DAOMC 250799T = CBS 141929 = DTO 356H7 = KAS 6176||House dust, Canada||KX450910||KX450905||KX450892||KX450897|
|Aspergillus megasporus||DAOMC 250800 = DTO 356H1 = KAS 5973||House dust, Canada||KX450909||KX450904||KX450891||KX450896|
|Aspergillus megasporus||CBS 141772 = DTO 048I3||Dutch chocolate butter, the Netherlands||KX450911||KX450906||KX450893||KX450898|
|Aspergillus montevidensis||CBS 491.65T; NRRL 108; ATCC 10077; IMI 172290; IHEM 3337||Human tympanic membrane, unknown||EF652077||EF652020||EF651898||EF651964|
|Aspergillus montevidensis||CBS 518.65; NRRL90; ATCC 16464; IMI 229971; IFO 33018||Unknown, USA||EF652076||EF652017||EF651897||EF651963|
|Aspergillus montevidensis||NRRL 4716; IMI 350348||Candied grapefruit rind, USA||EF652079||EF652018||EF651899||EF651965|
|Aspergillus montevidensis||NRRL 89; ATCC 10065; IMI 211806||Unknown||EF652075||EF652016||EF651896||EF651962|
|Aspergillus neocarnoyi||CBS 471.65T; NRRL126; ATCC 16924; IMI 172279||Unknown||EF652057||EF651985||EF651903||EF651942|
|Aspergillus niveoglaucus||CBS 101750; AS 3.4665||Soil, China||HE615135||HE801323||HE801331||HE801312|
|Aspergillus niveoglaucus||CBS 114.27T; NRRL127; NRRL 129; NRRL 130; ATCC 10075; CBS 517.65; IMI 032050; IMI 032050ii||Unknown||EF652058||EF651993||EF651905||EF651943|
|Aspergillus niveoglaucus||NRRL 128; FRR 128; IMI 091871||Unknown||EF652059||EF651994||EF651906||EF651944|
|Aspergillus niveoglaucus||NRRL 136||Unknown||EF652062||EF651995||EF651909||EF651945|
|Aspergillus niveoglaucus||NRRL 137; IMI 091872||Unknown||EF652063||EF651996||EF651910||EF651946|
|Aspergillus osmophilus||CBS 134258T; IRAN 2090C||Leaf of Triticum aestivu, Iran||KC473921||KC473918||KC473924||KX512310|
|Aspergillus proliferans||CBS 121.45T; NRRL 1908; CBS 528.65; ATCC 16922; IMI 016105; IMI 016105ii; IMI 016105iii; MUCL 15625||Cotton yarn, United Kingdom||EF652064||EF651988||EF651891||EF651941|
|Aspergillus proliferans||NRRL 114; ATCC 10076; IMI 211808||Unknown, USA||EF652051||EF651987||EF651886||EF651933|
|Aspergillus proliferans||NRRL 62482; CCF 4096||Palm skin, Czech Republic||FR848827||HE650908||FR775375||HE801303|
|Aspergillus proliferans||NRRL 62494; CCF 4146||Toenail, Czech Republic||HE578067||HE650909||HE578076||HE801304|
|Aspergillus proliferans||NRRL 62497; CCF 4115||Toenail, Czech Republic||FR851850||HE578090||FR851855||HE578107|
|Aspergillus proliferans||NRRL 71||Leafhoppers, USA||EF652047||EF651986||EF651885||EF651932|
|Aspergillus pseudoglaucus||CBS 123.28T; NRRL 40; ATCC 10066; IMI 016122; IMI 016122ii; MUCL 15624||Unknown||EF652050||EF652007||EF651917||EF651952|
|Aspergillus pseudoglaucus||CBS 379.75; IMI 278373; ETH 8218; DSM 1370||Leaf from Vaccinium myrtillus, Switserland||HE615131||HE801322||HE801336||HE801311|
|Aspergillus pseudoglaucus||CBS 529.65; NRRL13; NRRL 24; ATCC 9294; IMI 016114; IMI 016114ii; MUCL 15649||Prunus domestica, France||EF652048||EF652005||EF651915||EF651950|
|Aspergillus pseudoglaucus||CBS101747; AS 3.4674||Animal dung, China||HE615130||HE801321||HE801335||HE801310|
|Aspergillus pseudoglaucus||NRRL 17; ATCC 10079; UAMH 6580||Skin from wrist, USA||EF652049||EF652006||EF651916||EF651951|
|Aspergillus ruber||CBS 101748; AS 3.4632||Soil, China||HE615134||HE801325||HE801337||HE801315|
|Aspergillus ruber||CBS 464.65; NRRL5000; ATCC 16923; IMI 32048||Coffee beans, United Kingdom||EF652080||EF652010||EF651922||EF651949|
|Aspergillus ruber||CBS 530.65T; NRRL 52; ATCC 16441; IMI 211380||Unknown||EF652066||EF652009||EF651920||EF651947|
|Aspergillus ruber||NRRL 76; IMI 91868||Unknown||EF652067||EF652011||EF651921||EF651948|
|Aspergillus sloanii||CBS 138176; DTO 244-I8||House dust, United Kingdom||KJ775539||KJ775308||KJ775073||KX463364|
|Aspergillus sloanii||CBS 138177T; DTO 245-A1||House dust, United Kingdom||KJ775540||KJ775309||KJ775074||KX463365|
|Aspergillus sloanii||CBS 138178; DTO 245-A8||House dust, United Kingdom||KJ775542||KJ775313||KJ775076||KX450900|
|Aspergillus sloanii||CBS 138179; DTO 245-A9||House dust, United Kingdom||KJ775543||KJ775314||KJ775077||KX450901|
|Aspergillus sloanii||CBS 138231; DTO 245-A6||House dust, United Kingdom||KJ775541||KJ775311||KJ775075||KX450899|
|Aspergillus tonophilus||CBS 405.65T; NRRL 5124; ATCC 14567; ATCC 16440; ATCC 36504; DSM 3462; IFO 6529; IMI 108299; IMI 108299ii||Binocular lens, Japan||EF652081||EF652000||EF651919||EF651969|
|Aspergillus xerophilus||CBS 938.73T; NRRL6131; FRR 2804; IMI 278377||Desert soil, Egypt||EF652085||EF651983||EF651923||EF651970|
|Aspergillus xerophilus||NRRL 6132||Desert soil, Egypt||EF652086||EF651984||EF651924||EF651971|
The ITS alignment was 535 bp long and contained 68 variable characters, of which 27 were parsimony informative. MP analysis resulted in two equally parsimonious trees (length 79 steps, CI = 0.987, RI = 0.992). HKY+I was found to be the most suitable model for BI analysis. ITS is highly conserved in sect. Aspergillus, as demonstrated in the phylogenetic analysis, making it uninformative as an identification barcode in section Aspergillus. Of the 22 species, including the two new species described here, only A. cumulatus, A. leucocarpus, A. osmophilus and A. xerophilus have unique ITS barcodes. The alignments for the BenA, CaM and RPB2 datasets were respectively 389 (151 variable, 136 parsimony informative), 556 (221 variable, 177 parsimony informative) and 871 bp (202 variable, 162 parsimony informative) long. MP analyses resulted in 84 (length 287 steps, CI = 0.728, RI = 0.923), 12 (length 275 steps, CI = 0.7, RI = 0.904), 28 (length 364 steps, CI = 0.648, RI = 0.911) and 24 (length 798 steps, CI = 0.692, RI = 0.907) equally parsimonious trees for BenA, CaM, RPB2 and concatenated dataset. K80+G (BenA), SYM+G (CaM) and SYM+I+G (RPB2) were the most suitable models for BI.
Tree topologies did not differ for respective genes between MP and BI; therefore, MP trees were used to present results. Some species are consistently resolved as sister species such as A. proliferans and A. glaucus, A. brunneus and A. niveoglaucus, A. montevidensis and A. intermedius, and A. osmophilus and A. xerophilus. On a deeper level, however, the backbones in all gene trees were generally poorly supported, resulting in inconsistent clades among different gene trees. The addition of more newly discovered species of section Aspergillus in future may result in better backbone support. With regards to the new species, A. mallochii was sister to A. appendiculatus, although RPB2 placed it on a unique branch. Aspergillus megasporus resolves in different positions depending on gene analyzed, but based on the concatenated phylogeny belongs in a clade with A. brunneus, A. niveoglaucus, A. neocarnoyi, A. glaucus and A. proliferans. For species identifications, it is clear that all three of these genes are superior to ITS and distinguish between all 22 accepted species in sect. Aspergillus.
Aspergillus mallochii and A. megasporus produced several related tryptophan derived alkaloids including, echinulins, neoechinulins and isoechinulins, but in varying amounts (Table
Base peak chromatograms observed in positive ionization mode. a Aspergillus mallochii (DAOMC 146054 = KAS 7618) b Aspergillus megasporus (DAOMC 250799 = KAS 6176). Both species show some production of echinulin class of alkaloids to varying amounts. Quinolactacin A1, A2 and B were not detected in A. mallochii.
Overview of the major extrolites detected and product ions.
|Extrolite||m/z||Formula||RT (min)||Product ions m/z|
Latin, mallochii, named after Prof. David Malloch, a Canadian specialist in ‘Plectomycetes’ who first collected this species in the 1960’s.
USA, California, San Mateo, pack rat dung, added to DAOMC in 1969, collected by David Malloch, Holotype DAOM 740296, culture ex-type DAOMC 146054 = CBS 141928 = DTO 357-A5 = KAS 7618.
The Netherlands, ‘chocolat miroir’ icing for a cake, unknown date and collector, culture CBS 141776 = DTO 343-G3.
7 d (in mm), 25 °C. CYA 6–8; CY20S 14–17; MEA 3–4; MEA20S 29–31; DG18 48–50; YES 9–10; M40Y 48–50; MY50G 35–40; MY10-12 29–30; CY20S, DG18, MEA20S at 37 °C no growth; CREA no growth.
CYA: Colonies with restricted growth; conidiophores sparse; cleistothecia absent. CY20S: Colonies grow faster than on CYA; sporulation sparse to moderately dense, greyish to dark green (30E5–F5); cleistothecia dark yellow, abundant at colony centre. MEA: Colonies with restricted growth; conidiophores and cleistothecia absent. MEA20S: Colonies grow faster than on MEA; sporulation sparse, greyish to dark green (30E5–F5); cleistothecia yellow to orange, abundant. DG18: Colonies very fluffy with aerial mycelia giving rise to conidiophores; sporulation sparse to moderately dense, greyish to dark green (30E5–F5); cleistothecia abundant at colony centre, yellow to orange. Homothallic.
Cleistothecia eurotium-like, wall consisting of one layer of flattened cells, yellow to orange, turning deep brown with age, globose, 95–250 μm diam. Asci eight-spored, globose, ellipsoidal to pyriform, 10–15 μm diam, maturing after 7–14 d. Ascospores lenticular, equatorial crest present but incomplete, convex surface roughened, 4.5–6 × 3.5–4.5 μm (5.1±0.3 × 3.9±0.3), n = 52. Conidiophores radiate and columnar, uniseriate; stipes smooth, 200–1000 × 7.5–17(–19) μm; vesicle globose, (25–)40–65 μm diam; phialides ampulliform, covering 80–100% of vesicle, 7–11 × 3–5 μm; conidia roughened to spiny, ellipsoidal, connectives easily visible, 4.5–6.5 × 4–5.5 μm (5.4±0.4 × 4.5±0.3), average width/length = 0.83, n = 68.
Isoechinulin A, B & C; neoechinulin A & B; unknowns C20H18O9, C19H32O3N2, C19H21O3N3, C24H30O3N3, C39H43O6N5. Additionally, echinulin, erythroglaucin, auroglaucin, flavoglaucin, dihydroauroglaucin, tetrahydroauroglaucin were found in CBS 141776. Some extrolites tentatively identified as tetracyclic compounds were detected in CBS 141776.
Aspergillus mallochii is phylogenetically and morphologically most similar to A. appendiculatus. Both are unable to grow at 37 °C and both have ascospores with incomplete equatorial furrows. Ascospores of the new species, however, are generally smaller and at least finely roughened compared to the smoother ascospores of A. appendiculatus.
Latin, megasporus, in reference to the large conidia produced by this species.
Canada, Nova Scotia, Wolfville, house dust, 29 January 2015, collected by Allison Walker, isolated by Cobus M. Visagie, holotype DAOM 741781, culture ex-type DAOMC 250799 = CBS 141929 = DTO 356-H7 = KAS 6176.
Canada, New Brunswick, Little Lepreau, house dust, 29 January 2015, collected by Allison Walker, isolated by Cobus M. Visagie, culture DAOMC 250800 = DTO 356-H1 = KAS 5973. The Netherlands, Dutch chocolate butter, August 2007, collected and isolated by Martin Meijer, culture CBS 141772 = DTO 048-I3.
7 d (in mm), 25 °C. CYA 3–8; CY20S 30–35; MEA 3–5; MEA20S 24–35; DG18 47–50; YES 15–16; M40Y 45–47; MY50G 35–40; MY10-12 40–44; CY20S, DG18, MEA20S at 37 °C no growth, CREA no growth.
CYA: Colonies with restricted growth; conidiophores and cleistothecia absent. CY20S: Colonies grow faster than on CYA; sporulation moderately dense, greyish to dark green (30E5–F5); cleistothecia yellow, sparse. MEA: Colonies with restricted growth; conidiophores and cleistothecia absent. MEA20S: Colonies grow faster than on MEA; sporulation moderately dense, greyish to dark green (30E5–F5); cleistothecia yellow, moderately abundant. DG18: Colonies very fluffy with abundant aerial mycelia giving rise to conidiophores; sporulation moderately dense, dull to dark green (28E3–F3); cleistothecia abundant, dark yellow to orange. Homothallic.
Cleistothecia eurotium-like, wall consisting of one layer of flattened cells, yellow to orange, globose, 115–205 μm diam. Asci eight-spored, globose, ellipsoidal to pyriform, 14–19.5 μm diam. Ascospores lenticular, equatorial crest roughened, convex surface smooth, 5–8 × 3.5–6 μm (6.4±0.6 × 4.9±0.5), n = 51. Conidiophores radiate and columnar, uniseriate; stipes smooth, (30–)60–1000 × (9–)13–20 μm; vesicle globose, (8.5–)20–60 μm diam; phialides ampulliform, covering 70–100% of vesicle, (9–)11–15 × 5–7 μm; conidia roughened to spiny, ellipsoidal, connectives often visible, 7–12 × 6–8.5 μm (9.5±1.0 × 6.9±0.5), average width/length = 0.72, n = 85.
Echinulin; neoechinulin A & B; preechinulin; quinolactacin A1 & A2; unknowns C15H20O2, C21H37N, C24H30O6, C29H37O2N3, C21H44O2. In addition, asperflavin, emodin, erythroglaucin, physcion and bisanthron were found in CBS 141772. Some additional extrolites, tentatively identified as tetracyclic compounds, were detected in CBS 141772
The concatenated phylogeny of BenA, CaM and RPB2 resolves A. megasporus in a clade with A. brunneus, A. niveoglaucus, A. neocarnoyi, A. glaucus and A. proliferans. None of these species are able to grow on CY20S at 37 °C. Aspergillus niveoglaucus and A. megasporus can be distinguished from other species by their large conidia, which are up to 11 and 12 μm in the longest axis respectively. Aspergillus megasporus colonies grow faster than A. niveoglaucus on DG18.
Species of Aspergillus section Aspergillus are xerophilic and widespread in nature. Indoor environments, including homes and public buildings, are designed to be as dry as possible, especially in temperate countries, and these conditions select for these xerophiles to thrive. This partially explains the dominance of Aspergillus, Penicillium, Cladosporium and Wallemia in indoor fungal communities (
Aspergillus megasporus was isolated from Canadian house dust collected in Wolfville, Nova Scotia and Little Lepreau, New Brunswick, and was also isolated from chocolate butter in the Netherlands. Phylogenetically, the position of this species varies depending on which gene is analysed; CaM resolves it in its own distinct clade, BenA in a clade with a poorly supported branch with A. glaucus and A. proliferans, and RPB2 closest to A. niveoglaucus. The multigene phylogeny places it in a large clade, including A. brunneus, A. niveoglaucus, A. neocarnoyi, A. glaucus and A. proliferans. Both A. niveoglaucus and A. megasporus produces conidia respectively reaching 11 and 12 µm, easily distinguishing them from other species of section Aspergillus. Aspergillus megasporus can be distinguished from A. niveoglaucus based on its faster growth on DG18. Aspergillus megasporus produces extrolites commonly detected in species of section Aspergillus, including echinulin, neoechinulin and preechinulin. However, we also detected quinolactacin, a first report for the group. In an independent study using different methods and media, compounds detected from CBS 141772 include asperflavin, auroglaucin, bisanthrons, dihydroauroglaucin, echinulin, emodin, erythroglaucin, flavoglaucin, isoechinulins, neoechinulins, preechinulin, physcion, quinolactacin, tetracyclic compounds, and tetrahydroauroglaucin (Frisvad, personal communication).
Aspergillus mallochii was isolated from pack rat dung collected from San Mateo, California, USA. An additional strain was recently isolated from ‘Chocolat miroir’ icing for a cake in the Netherlands. Phylogenetically, it has A. appendiculatus as sister species, originally described by
Quinolactacin A1, A2 & B were the major compounds produced by A. megasporus, the only species of section Aspergillus that produces these. These quinolone structures with a γ-lactam ring were first characterized from fermentations of an unknown Penicillium species (
Recently, the International Code of Nomenclature for algae fungi and plants (ICN, Melbourne Code; (
This research was supported by a grant from the Alfred P. Sloan Foundation Program on the Microbiology of the Built Environment. We thank our dust collectors, Allison Walker, Bryce Kendrick and Anthony Amend.