Fungal diversity
Table 1 shows the identity of the twenty-two fungal strains studied. The highest number of strains corresponded to Auxarthron umbrinum (4), followed by Auxarthron alboluteum (2), Auxarthron conjugatum (2), and Malbranchea aurantiaca (2). Auxarthron zuffianum, Currahmyces indicus and Malbrancea flocciformis were represented by one strain each. Eight strains were only identified at genus-level (three belonging to Malbranchea, two to Spiromastigoides, two to Arachnomyces, and one to Arthropsis), one strain (FMR 17684) only at family-level (Onygenaceae).
Molecular phylogeny
Our phylogenetic study included 92 sequences corresponding to 75 species with a total of 1,213 characters (700 ITS and 513 LSU) including gaps, of which 579 were parsimony informative (402 ITS and 177 LSU). The ML analysis was congruent with that obtained in the BI analysis, both displaying trees with similar topologies. The datasets did not show conflict with the tree topologies for the 70% reciprocal bootstrap trees, which allowed the two genes to be combined for the multi-locus analysis.
Twenty of our strains were placed into a main clade corresponding to the members of the Onygenales (100% BS / 1 PP), while two were placed in the Arachnomycetales (100% BS / 1 PP) (Fig. 2). The Onygenales clade was divided into eight clades corresponding to the families Onygenaceae (100% BS / 1 PP), Gymnascaceae (98% BS / 1 PP), Nannizziopsiaceae (100% BS / 1 PP), Helicoarthrosporaceae (100% BS / 1 PP), Arthrodermataceae (100% BS / 1 PP), Ajellomycetaceae (97% BS / 1 PP), Ascosphaeraceae (100% BS / 1 PP), and Spiromastigaceae (92% BS / 0.99 PP), which included a basal terminal branch for Pseudospiromastix tentaculata. Most of our strains (17/22) were distributed into several subclades of the Onygenaceae: 15/22 into Auxarthron/Malbranchea subclade (100% BS / 1 PP), one into a terminal branch (FMR 17683) together Currahmyces indicus (100% BS / 1 PP), and another one (FMR 17684) into a distant, independent terminal branch. One strain (FMR 17692) was placed into the Gymnascaceae, in a terminal branch together with Arthropsis cirrhata (100% BS / 1 PP). The Spiromastigaceae included the last two strains (FMR 17686 and FMR 17696), placed into a terminal branch together Malbranchea gypsea (100% BS / 1 PP).
Taxonomy
Since the strains FMR 17685 and FMR 17691 represented two species of Arachnomyces that were different from the other species of the genus, they are proposed as new, i.e. Arachnomyces bostrychodes and Arachnomyces graciliformis, respectively.
Arachnomyces bostrychodes Rodr.-Andr., Cano & Stchigel, sp. nov. Fig. 3. MycoBank MB 834921.
Etymology: From Greek βοστρυχος-, curl, due to the appearance of the reproductive hyphae.Diagnosis: The phylogenetically closest species to Arachnomyces bostrychodes is A. peruvianum (Fig. 2). Nevertheless, Arachnomyces botrychodes lacks of a sexual morph and racket hyphae (both present in A. peruvianum), and produces longer conidia than A. peruvianum (4.0–8.0 × 1.0–2.0 μm vs. 4.0–5.0 × 1.0–3.0 μm); also, A. bostrychodes grows more slowly on OA (13–14 mm diam. after 14 days at 25 ºC) than A. peruvianum (30 mm diam.) (Cain 1957, Brasch et al. 2016). Arachnomyces bostrychodes resembles morphologically Arachnomyces gracilis, but the former grows faster, and produces more twisted branches and lacks sexual morph.Type: United States of America: Texas, from a human´s scalp, 2008, N. Wiederhold (CBS H-24452 – holotype; CBS 146926 = FMR 17685 = UTHSCSA DI18-91 – ex-type cultures; LSU sequences GenBank LR701766).Description: Vegetative hyphae hyaline, septate, branched, smooth- and thin-walled, 1.0–2.0 μm wide. Fertile hyphae well-differentiated, arising as lateral branches from the vegetative hyphae, successively branching to form dense clusters, arcuate, sinuous, contorted or tightly curled, 1.0–2.0 μm wide, forming randomly intercalary and terminally arthroconidia. Conidia enteroarthric, hyaline, one-celled, smooth-walled, cylindrical, barrel-shaped, and finger-like-shaped when terminal, 4.0–8.0 × 1.0–2.0 μm, mostly curved and truncated at one or (mostly) both ends, separated from the fertile hyphae by rhexolysis. Chlamydospores, racquet hyphae, setae, and sexual morph not observed.
Culture characteristics: Colonies on PYE reaching 19–20 mm diam. after 2 weeks at 25 °C, elevated, cottony, margins regular, white (5A1), sporulation absent; reverse light orange (5A4). Colonies on PDA reaching 11–12 mm diam. after 2 weeks at 25 °C, elevated, velvety with floccose patches, margins regular, yellowish white (4A2), sporulation abundant; reverse greyish yellow (4B6). Colonies on PDA reaching 13–14 mm diam. after 2 weeks at 30 ºC, slightly elevated, velvety to floccose, regular margins, white (4A1), sporulation sparse; reverse, greyish yellow (4B6). Colonies on OA researching 13–14 mm diam. after 2 weeks at 25 °C, flattened, smooth and granulose, irregular margins, yellowish white (2A2) at centre and light yellow (2A5) at edge, sporulation abundant. Exudate and diffusible pigment absent.
Minimum, optimal and maximum temperature of growth (on PDA): 10 °C, 30 °C, and 37 °C, respectively. Non-haemolytic. Casein not hydrolysed. Not inhibited by cycloheximide. Urease and esterase (TOTM) tests positive. Growth occurs at NaCl 10 % w/w, but not at 20 % w/w.
Arachnomyces graciliformis Rodr.-Andr., Stchigel & Cano, sp. nov. Fig. 4. MycoBank MB 834923.
Etymology: Because the morphological similarity with Arachnomyces gracilis.Diagnosis: Arachnomyces graciliformis is phylogenetically close to A. glareosus and to A. minimus (Fig. 2). These three species form common clade together with A. nodosetosus and A. jinanicus (84 BS / 1 PP). Unlike A. glareosus and A. minimus, A. graciliformis does not produces racquet hyphae nor sexual morph (Gibas et al. 2004) but produces longer conidia than A. glareosus (4.0–10.0 × 1.5–2.0 μm vs. 2.5–4.5 × 1.5–2.0 μm), which are not produced by A. minimus. Arachnomyces graciliformis resembles morphologically Arachnomyces gracilis, but the former grows more slowly, produces more twisted fertile branches and does not form a sexual morph (Udagawa & Uchiyama 1999).Type: United States of America: Massachusetts, from an animal´s bone, 2012, N. Wiederhold (CBS H-24453 – holotype; CBS 146927 = FMR 17691 = UTHSCSA DI18-97 – ex-type cultures; LSU sequence GenBank LR743668).Description: Vegetative hyphae hyaline, septate, branched, smooth- and thin-walled, 1.0–2.0 μm wide. Fertile hyphae well-differentiated, arising as lateral branches from the vegetative hyphae, branching repeatedly, sinuous to arcuate or apically coiled, 1.5–2.0 μm wide, forming randomly intercalary and terminally arthroconidia. Conidia enteroarthric, hyaline, unicellular, smooth- and thin-walled, cylindrical or finger-like-shaped when terminal, 4.0–10.0 × 1.5–2.0 μm, mostly curved, detached from the fertile hyphae by rhexolysis. Chlamydospores, racquet hyphae, setae, and sexual morph not observed.
Culture characteristics: Colonies on PYE reaching 12–13 mm diam. after 2 weeks at 25 °C, elevated, velvety to floccose, margins regular, slightly furrowed, yellowish white (3A2), sporulation absent; reverse greyish orange (5B3). Colonies on PDA reaching 9–10 mm diam. after 2 weeks at 25 °C, slightly elevated, velvety to floccose, margins regular, slightly furrowed, yellowish white (1A2), sporulation absent; reverse greyish yellow (4B3). Colonies on PDA reaching 3–4 mm diam. after 2 weeks at 30 ºC, slightly elevated, velvety to floccose, margins regular, slightly furrowed, yellowish white (1A2), sporulation absent; reverse, greyish yellow (4B3). Colonies on OA researching 6–7 mm diam. after 2 weeks at 25 °C, flattened, velvety and granulose, margins irregular, pale yellow (4A3), sporulation absent (conidia appear after 5-6 weeks incubation). Exudate and diffusible pigment absent. Minimum, optimal and maximum temperature of growth (on PDA): 10 °C, 25 °C, and 30 °C, respectively. Non-haemolytic. Casein not hydrolysed. Not inhibited by cycloheximide. Urease and esterase tests positive. Growth occurs at NaCl 10 % w/w, but not at 20 % w/w.
Dichotomous key to Arachnomyces (adapted from Sun et al. 2019).
1a. Homothallic; asexual morph present or not....................................................................... 2
1b. Heterothallic; asexual morph present ............................................................................... 6
2a. Peridial setae coiled or circinate; asexual morph absent................................................... 3
2b. Peridial setae straight, tapering towards the apex; asexual morph arthroconidia……………........................................................................................ A. gracilis
3a. Peridial setae slightly nodose; ascospores mostly < 3.5 μm diameter……..………….... 4
3b. Peridial setae smooth-walled; ascospores mostly > 3.5μm diamater................................ 5
4a. Ascospores smooth-walled................................................................................ A. minimus
4b. Ascospores echinulate .................................................................................. A. peruvianus
5a. Ascomata 100–300 μm diameter.......................................................................... A. nitidus
5b. Ascomata 500–700 μm diam......................................................................... A. sulphureus
6a. Arthroconidia alternate...................................................................................................... 7
6b. Arthroconidia in persistent chains................................................................................... 12
7a. Arthroconidia cylindrical or barrel-shaped; sclerotia present........................................... 8
7b. Arthroconidia distinct; sclerotia absent..............................................................................9
8a. Colonies becoming greyish brown, not growing at 35 ºC................................. A. glareosus
8b. Colonies white to pale brown, growing at 35 ºC............................................. A. scleroticus
9a. Arthroconidia subglobose to pyriform............................................................................. 10
9b. Arthroconidia cylindrical to finger-like-shaped.............................................................. 11
10a. Arthroconidia smooth-walled to finely asperulate; setae (produced on the vegetative mycelium) smooth-walled to slightly nodose............................................................... A. kanei
10b. Mature arthroconidia coarsely verrucose; setae (produced on the vegetative mycelium) strongly nodose......................................................................................................... A. pilosus
11a. Fertile hyphae successively branching to form dense clusters, arcuate, sinuous, contorted or tightly curled............................................................................................... A. bostrychodes
11b. Fertile hyphae branching but not in clusters; branches only apically coiled............................................................................................................... A. graciliformis
12a. Setae (produced on the vegetative mycelium) strongly nodose, circinate or loosely coiled at the apex......................................................................................................... A. nodosetosus
12b. Setae (produced on the vegetative mycelium) strongly nodose, tip straight................................................................................................................... A. jinanicus
Since the strain FMR 17692 was placed in the same terminal clade than Arthropsis cirrhata, while the type species of the genus (Arthropsis truncata) is phylogenetically far away (into the order Sordariales; Giraldo et al. 2013), we propose the erection of the new genus Pseudoarthropsis for A. cirrhata, and the new species Pseudarthropsis crassispora.
Pseudoarthropsis Stchigel, Rodr.-Andr. & Cano, gen. nov. MycoBank MB 834925.
Etymology: From Greek ψευδής-, resembling, because the morphological semblance to Arthropsis.
Diagnosis: Mycelium composed by hyaline to orange, septate hyphae. Conidiophores consisting in fertile lateral branches and a part of the main hyphae, which disarticulate in yellowish orange, thin-walled, cylindrical to cuboid enteroarthric conidia, or in hyaline, thick-walled, ellipsoidal, globose to barrel-shaped holoarthric conidia.
Type species: Pseudoarthropsis cirrhata (Oorschot & de Hoog) Stchigel, Rodr.-Andr. & Cano.
Pseudoarthropsis cirrhata (Oorschot & de Hoog) Stchigel, Rodr.-Andr. & Cano, comb. nov. MycoBank MB 834928.
Basionym: Arthropsis cirrhata Oorschot & de Hoog, Mycotaxon 20: 130 (1984).
Description: Vegetative hyphae septate, pale yellowish orange, smooth- and thin-walled, dichotomously branched, 2–3 μm wide. Fertile hyphae well differentiated, arising at right angles as recurved lateral branches of the vegetative hyphae, forming septa basipetally to produce chains of enteroarthric conidia. Arthroconidia yellowish orange, smooth- and thin-walled, cylindrical to cuboid, often broader than long, 2.5–4.0 × 2–3 μm, truncated at both ends, separated by trapezoid connectives, secession rhexolytic. Colonies on PYE reaching 4–5 mm diam. after 10 days at 25 °C, powdery, fealty, slightly raised, orange (5A7), pale orange (5A5) at centre; reverse brownish orange (7C8), diffusible pigment brown.
Type: CBS 628.83, 1984, from a wall near Schiphol, The Netherlands, collector C.A.N. van Oorschot.
Pseudoathropsis crassispora Rodr.-Andr., Stchigel & Cano, sp. nov. Fig. 5. MycoBank MB 834930.
Etymology: From Latin crassus-, thick, and -sporarum, spore, because of the thick wall of the conidia.Diagnosis: Pseudoarthropsis crassispora is phylogenetically close to P. cirrhata. Nevertheless, the former produces holoarthric conidia, while they are enteroarthric in the latter. Also, the conidia of P. crassispora are ellipsoidal, globose or broadly barrel-shaped, while these are cylindrical to cuboid (often wider than they are long) in P. cirrhata (van Oorschot & de Hoog 1984). Moreover, the conidia are bigger in P. crassispora than in P. cirrhata (4.5–5.5 × 2.5–3.5 μm vs. 2.5–4.0 × 2.0–3.0 μm). Also, P. crassispora grows faster than P. cirrhata (on PYE at 25 ºC), and the maximum temperature of growth is at 37 ºC and 30 ºC, respectively.Type: United States of America: Minnesota, from a human´s bronchial washing, 2012, N. Wiederhold (CBS H-24454 – holotype; CBS 146928 = FMR 17692 = UTHSCSA DI18-98 – ex-type cultures; LSU sequence GenBank LR701763).Description: Vegetative hyphae septate, hyaline, smooth- and thin-walled, mostly straight, occasionally branched, 1.5–2.0 μm wide. Fertile hyphae well-differentiated, arising as lateral branches of the vegetative hyphae, hyaline, septate, smooth- and thin-walled, erect, simple or branched up to 3 times at the apex, stipe 10–20 × 1.5–2.0 μm, branches 10–70 × 1.5–2.0 μm, forming septa basipetally to produce chains of arthroconidia. Conidia holoarthric, unicellular, hyaline, smooth- and thick-walled, ellipsoidal, globose or barrel-shaped, transiently presents as bi-cellular conidia, 2.5–3.5 × 4.5–5.5 μm, in chains of up to 20, separate from the fertile hyphae by schizolysis, rarely by rhexolysis. Chlamydospores, racquet hyphae, setae, and sexual morph not observed.
Culture characteristics: Colonies on PYE reaching 13–14 mm diam. after 2 weeks at 25 °C, slightly elevated, velvety, margins regular, furrowed, yellowish white (3A2) and yellowish grey (4B2) at centre, sporulation abundant; reverse pale yellow (4A3. Colonies on PDA reaching 14–15 mm diam. after 2 weeks at 25 °C, flattened, velvety, margins regular, greenish white (30A2) and pastel green (30A4) at centre, sporulation abundant; reverse pastel yellow (3A4). Colonies on PDA reaching 15–16 mm diam. after 2 weeks at 30 ºC, slightly elevated, velvety, margins regular, furrowed, yellowish white (3A2), sporulation sparse; reverse yellow (3A6), with a scarce production of yellowish diffusible pigment. Colonies on OA researching 10–11 mm diam. after 2 weeks at 25 °C, flattened, velvety to floccose, margins irregular, greenish white (30A2) and pale green (28A3) at centre, sporulation abundant. Exudate and diffusible pigment absent, except on PDA. Minimum, optimal and maximum temperature of growth on PDA: 10 °C, 30 °C, and 37 °C, respectively. Non-haemolytic. Casein hydrolyzed without pH change. Not inhibited by cycloheximide. Urease and esterase tests positive. The fungus grows up to NaCl 10 % w/w, but not at 20 % w/w.
Due to the strain FMR 17683 being placed into a terminal branch of the Onygenaceae together with Currahmyces indicus (Sharma & Shouche 2019), and because they differ molecularly and phenotypically, we propose the erection of the new species Currahmyces sparsispora.
Currahmyces sparsispora Rodr.-Andr., Cano & Stchigel, sp. nov. Fig. 6. MycoBank MB 835692.
Etymology: From Latin sparsa-, splashed, -sporarum, spore, due to the disposition of the conidia along the hyphae.
Diagnosis: Currahmyces sparsispora is phylogenetically close to Currahmyces indicus; however, they can be differentiated because the former has broader hyphae (1.5–2.0 μm vs. 0.7–1.1 μm) and lacks a sexual morph (typical gymnothecial ascomata are produced on hair-baited soil plates by C. indicus).
Type: United States of America: Florida, from human sputum, 2007, N. Wiederhold (CBS H-24455 – holotype; CBS 146929 = FMR 17683 = UTHSCSA DI18-89 – ex-type cultures; LSU sequence GenBank LR723273).
Description: Vegetative hyphae septate, hyaline, smooth- and thin-walled, mostly straight, rarely branched, 1.5–2.0 μm wide. Fertile hyphae undifferentiated from the vegetative hyphae. Conidia enteroarthric, hyaline, unicellular, smooth- and thin-walled, disposed relatively far from each other along the fertile hyphae, separated by 1–2 evanescent connective cells, cylindrical to slightly barrel-shaped, 3.0–12.0 × 1.0–2.0 μm, separated by rhexolysis. Chlamydospores, racquet hyphae, setae, and sexual morph not observed.
Culture characteristics: Colonies on PYE reaching 27–28 mm diam. after 2 weeks at 25 °C, slightly elevated, velvety to floccose, margins regular, pale orange (5A3) at centre and white (5A1) at edge, sporulation sparse; reverse orange (5A6). Colonies on PDA reaching 23–24 mm diam. after 2 weeks at 25 °C, slightly elevated, velvety, margins regular, light orange (5A5) at centre and orange white (5A2) at edge, sporulation sparse; reverse deep orange (6A8). Colonies on PDA reaching 30–31 mm diam. after 2 weeks at 30 ºC, slightly elevated, velvety, slightly furrowed, margins regular, orange (5A6), sporulation sparse; reverse brownish orange (6C8). Colonies on OA reaching 20–21 mm diam. after 2 weeks at 25 °C, slightly elevated, velvety, margins regular, orange white (5A2) at centre and white (5A1) at edge, sporulation sparse. Exudate and diffusible pigment absent in all culture media tested. Minimum, optimal and maximum temperature of growth on PDA: 10 °C, 30 °C, and 37 °C, respectively. Haemolytic. Casein not hydrolysed. Not inhibited by cycloheximide. Urease and esterase tests positive. Growth occurs at NaCl 3 % w/w and 10 % w/w, but not at 20 % w/w.
Taking into account that Auxarthron and Malbranchea are congeneric, as has been in previous studies (Sigler et al. 2002, Sarroco et al. 2015) and here (Fig. 2), and that Malbranchea (Saccardo 1882) has historical priority (International Code of Nomenclature for algae, fungi, and plants; Turland et al. 2018) on Auxarthron (Orr, Kuehn and Plunkett 1963), we transfer the species of Auxarthron (Orr et al. 1963) to Malbranchea as follows:
Malbranchea californiensis (G.F. Orr & Kuehn) Rodr.-Andr., Stchigel & Cano, comb. nov.
MycoBank MB 835229.
Basionym: Auxarthron californiense G.F. Orr & Kuehn, Can. J. Bot. 41: 1442 (1963).
Synonym: Gymnoascus californiensis (G.F. Orr & Kuehn) Apinis, Mycol. Pap. 96: 12 (1964).
Malbranchea chlamydospora (M. Solé, Cano & Guarro) Rodr.-Andr., Cano & Stchigel, comb. nov. MycoBank MB 835230.
Basionym: Auxarthron chlamydosporum M. Solé, Cano & Guarro, Stud. Mycol. 47: 108 (2002).
Malbranchea compacta (G.F. Orr & Plunkett) Rodr.-Andr., Cano & Stchigel, comb. nov.
MycoBank MB 835231.
Basionym: Auxarthron compactum G.F. Orr & Plunkett, Can. J. Bot. 41: 1453 (1963).
Malbranchea concentrica (M. Solé, Cano & Guarro) Rodr.-Andr., Stchigel & Cano, comb. nov. MycoBank MB 835232.
Basionym: Auxarthron concentricum M. Solé, Cano & Guarro, Stud. Mycol. 47: 106 (2002).
Malbranchea conjugata (Kuehn) Rodr.-Andr., Cano & Stchigel, comb. nov. MycoBank MB 835233.
Basionym: Myxotrichum conjugatum Kuehn, Mycologia 47: 883 (1956) [1955].
Synonym: Auxarthron conjugatum (Kuehn) G.F. Orr & Kuehn, Mycotaxon 24: 148 (1985).
Malbranchea longispora (Stchigel, Y. Marín, Guarro & Cano) Rodr.-Andr., Stchigel & Cano, comb. nov. MycoBank MB 835235.
Basionym: Auxarthron longisporum Stchigel, Y. Marín, Guarro & Cano, Persoonia 31: 267 (2013).
Malbranchea ostraviensis (Hubka, Dobiášová & M. Kolařík) Rodr.-Andr., Cano & Stchigel, comb. nov. MycoBank MB 835236.
Basionym: Auxarthron ostraviense Hubka, Dobiášová & M. Kolařík, Med. Mycol. 50: 619 (2012).
Malbranchea pseudauxarthron (G.F. Orr & Kuehn) Rodr.-Andr., Stchigel & Cano, comb. nov. MycoBank MB835237.
Basionym: Auxarthron pseudauxarthron G.F. Orr & Kuehn, Mycologia 64: 67 (1972).
Malbranchea umbrina (Boud.) Rodr.-Andr., Cano & Stchigel, comb. nov. MycoBank MB 835238.
Basionym: Gymnoascus umbrinus Boud., Bull. Soc. mycol. Fr. 8: 43 (1892).
Synonym: Auxarthron brunneum (Rostr.) G.F. Orr & Kuehn, Can. J. Bot.41: 1446 (1963).
Auxarthron umbrinum (Boud.) G.F. Orr & Plunkett, Can. J. Bot. 41: 1449 (1963).
Auxarthron thaxteri (Kuehn) G.F. Orr & Kuehn, Mycologia 63: 200 (1971).
Gymnoascus subumbrinus A.L. Sm. & Ramsb., Trans. Br. Mycol. Soc. 5: 424 (1917) [1916].
Gymnoascus umbrinus var. thaxteri (Kuehn) Apinis, Mycol. Pap. 96: 14 (1964).
Myxotrichum brunneum Rostr., Bot. Tidsskr. 19: 216 (1895).
Myxotrichum thaxteri Kuehn, Mycologia 47: 878 (1956) [1955].
Malbranchea zuffiana (Morini) Rodr.-Andr., Stchigel & Cano, comb. nov. MycoBank MB 835239.
Basionym: Gymnoascus zuffianus Morini, Mem. R. Accad. Sci. Ist. Bologna, Ser. 4 10: 205 (1889).
Synonym: Auxarthron zuffianum (Morini) G.F. Orr & Kuehn, Can. J. Bot. 41: 1445 (1963).
We also revalidate the Malbranchea species listed below:
Malbranchea albolutea Sigler & J.W. Carmich., Mycotaxon 4(2): 416 (1976).
Synonym: Auxarthron alboluteum Sigler, Hambl. & Flis, Stud. Mycol. 47: 118 (2002).
Malbranchea filamentosa Sigler & J.W. Carmich., Mycotaxon 15: 468 (1982).
Synonym: Auxarthron filamentosum Sigler, Hambl. & Flis, Stud. Mycol. 47: 116 (2002).
Because in a Blast search using the ITS and LSU nucleotide sequences from the ex-type strains, Malbranchea circinata and Malbranchea flavorosea match with taxa into the family Myxotrichaceae, both species are excluded to the genus.
After examination of the lectotype of Auxarthron indicum (Patil & Pawar 1987), we concluded that this fungus must be excluded from Malbranchea because its sexual morph differs mainly from all species described for the former genus. Whereas Auxarthron indicum produces smooth-walled ellipsoidal ascospores and gymnothecial ascomata lacking of true appendages, in Malbranchea spp. the ascospores are globose and mostly ornamented, and the ascomata have appendages. Based on the fact that there is no type strain of this species, we consider it as invalid.
Consequently, an emended description of the genus Malbranchea is provided as follows:
Malbranchea Sacc. MycoBank MB 8833.
Vegetative hyphae septate, hyaline, smooth- and thin-walled, straight or branched. Asexual morph consisting in undifferentiated fertile hyphae, and/or well-differentiated lateral branches, curved or not, which form randomly or basipetally terminal and intercalary arthroconidia. Conidia enteroarthric, rarely holoarthric, unicellular, hyaline, smooth- and thin-walled, mostly cylindrical, barrel-shaped, or irregularly shaped, sometimes cylindrical, detached from the fertile hyphae by rhexolysis. Sexual morph (when present) consisting in ascomata formed by of an anastomosing network of orange to brown, ornamented or not thick-walled hyphae (gymnothecia), bearing elongate appendages and/or spine projections, within there are small, evanescent, inflated asci which forms eight globose to oblate ascospores, whose cell wall is ornamented with a (coarse or thin) reticulate pattern. Species homothallic or heterothallic, thermotolerant or thermophilic, keratinolytic, chitinolytic or cellulolytic.
Despite the strain FMR 17681 being placed phylogenetically close to Malbranchea ostraviense and Malbranchea umbrina, it differs genetically and phenotypically from both species, therefore we propose the new species Malbranchea gymnoascoidea as follows:
Malbranchea gymnoascoides Rodr.-Andr., Stchigel & Cano, sp. nov. Fig. 7. MycoBank
MB 835212.
Etymology: Because to the ascomata are morphologically like to those of Gymnoascus reessii.Diagnosis: Malbranchea gymnoascoides is phylogenetically close to M. ostraviensis and M. umbrina (Fig. 2). Nevertheless, M. gymnoascoides produces smaller ascomata (up to 250 μm diam. in M. gymnoascoides vs. up to 450 and up to 600 μm diam. in both, M. ostraviensis and M. umbrina, respectively) (Orr et al. 1963, Hubka et al. 2013). Also, the peridial appendages of M. gymnoascoides are longer than those of M. umbrina (250–400 μm vs. 5–72 μm), but shorter than those of M. ostraviensis (of 350–600 μm long). The ascospores of M. gymnoascoides are like to those of M. ostraviensis (smooth-walled under the bright field microscope, oblate to globose, 2.5–3.5 μm diam), whereas those of M. umbrina are lenticular and measure 2.8–4.0 × 2.1–2.6 μm. Moreover, the arthroconidia of M. gymnoascoides are larger than those of M. umbrina (6.0–10.0 × 1.5–2.0 μm and 2.6–7.0 × 1.4 μm, respectively). Malbranchea ostraviensis also produces a pinkish to red diffusible pigment on MEA, PDA and SDA, a feature not observed in M. gymnoascoides nor in M. umbrina. Both Malbranchea gymnoascoides as well as of M. umbrina can grow slowly at 35 ºC, whereas the maximum temperature of growth for M. ostraviensis is of 32 ºC.Type: United State of America: Texas, from human’s bronchial washing, 2005, N. Wiederhold (CBS H-24456 – holotype; CBS 146930 = FMR 17681 = UTHSCSA DI18-87 – ex-type cultures; LSU sequence GenBank LR701758).
Description: Vegetative hyphae septate, hyaline, smooth- and thin-walled, mostly straight, rarely branched, 1.5–2.5 μm wide. Asexual morph consisting in undifferentiated fertile hyphae which form randomly intercalary and terminally arthroconidia. Conidia enteroarthric, unicellular, hyaline, smooth- and thin-walled, mostly barrel-shaped, sometimes cylindrical or irregularly-shaped, 6.0–10.0 × 1.5–2.0 μm, detached by rhexolysis. Ascomata gymnothecial, solitary or in clusters, hyaline at first, becoming orange brown with the age, globose or nearly so, 130–250 μm diam. excluding the appendages, which cover entirely the surface. Peridial hyphae septate, orange brown, branching and anastomosing to form a reticulate network, asperulate, very thick-walled, 3.5–5.5 μm wide, fragmenting by the septa when ageing, with lateral appendages. Appendages 0–1-septate, orange brown, asperulate, thick-walled, progressively tapering towards the apex, apex sinuous, 250–400 μm long, connected by basal knuckle joints. Asci 8-spored, globose or nearly so, 4–7 μm diam., soon deliquescent. Ascospores unicellular, hyaline at first, yellowish in mass when mature, smooth-walled under bright field microscope, globose, 2.5–3.5 μm diam.
Culture characteristics: Colonies on PYE reaching 46–47 mm diam. after 2 weeks at 25 °C, slightly elevated, velvety to floccose, margins regular, pale orange (5A3) at centre and white (5A1) at edge, sporulation sparse; reverse orange (5A6). Colonies on PDA reaching 36–37 mm diam. after 2 weeks at 25 °C, slightly elevated, velvety, margins regular, light orange (5A5) at centre and orange white (5A2) at edge, sporulation sparse; reverse deep orange (6A8). Colonies on PDA reaching 31–32 mm diam. after 2 weeks at 30 °C, slightly elevated, velvety, margins regular, slightly furrowed, orange (5A6), sporulation sparse; reverse brownish orange (6C8). Colonies on OA reaching 21–22 mm diam. after 2 weeks at 25 °C, slightly elevated, velvety, margins regular, orange white (5A2) at centre and white (5A1) at edge, sporulation sparse. Exudate and diffusible pigment absent in all culture media tested. Minimum, optimal and maximum temperature of growth on PDA: 10 °C, 25 °C, and 35 °C, respectively. Non-haemolytic. Casein hydrolysed without pH change. Not inhibited by cycloheximide. Urease and esterase tests positive. Growth occurs at NaCl 10 % w/w, but not at 20 % w/w.
Despite the strain FMR 17695 being phylogenetically close to Malbranchea longispora, it differs phylogenetically and morphologically from it. Consequently, we propose the erection of the new species Malbranchea multiseptata.
Malbranchea multiseptata Rodr.-Andr., Cano & Stchigel, sp. nov. Fig. 8. MycoBank MB 835213.
Etymology: From Latin multi-, many, and –septatae, septa, because the vegetative hyphae are multiseptate.Diagnosis: Malbranchea multiseptata is phylogenetically linked to M. longispora. Nevertheless, M. multiseptata does not form chlamydospores nor a sexual morph as in M. longispora (Crous et al. 2013). Also, M. multiseptata produces shorter conidia (3.0–9.0 × 1.5–2.0 μm) than those of M. longispora (4.0–24.0 × 1.0–5.5 μm).Type: United States of America: Texas, from human’s bronchial washing, 2014, N. Wiederhold (CBS H-24457 – holotype; CBS 146931 = FMR 17695 = UTHSCSA DI18-101 – ex-type cultures; LSU sequence GenBank LR701760).Description: Vegetative hyphae hyaline, smooth- and thin-walled straight to sinuous, sparsely branched, 1.0–2.0 μm wide, becoming highly septate with the age, septa thickened. Fertile hyphae arising as lateral branches (sometimes arranged opposite each other) from the vegetative hyphae, unbranched, straight or slightly sinuous, 1.5–2.0 μm wide, forming randomly intercalary and terminally arthroconidia. Conidia enteroarthric, unicellular, hyaline, smooth- and thin-walled, separated by evanescent connective cells, cylindrical, 3.0–9.0 × 1.5–2.0 μm, rounded at the end when terminal, rhexolytic secession. Chlamydospores, racquet hyphae, setae, and sexual morph not observed.
Culture characteristics: Colonies on PYE reaching 35–36 mm diam. after 2 weeks at 25 °C, elevated, velvety to floccose, margins regular, white (5A1), sporulation sparse; reverse greyish yellow (4B4). Colonies on PDA reaching 34–35 mm diam. after 2 weeks at 25 °C, slightly elevated, velvety to floccose, margins regular, white (5A1), sporulation absent; reverse yellowish white (3A2). Colonies on PDA reaching 27–28 mm diam. after 2 weeks at 30 ºC, slightly elevated, velvety to floccose, margins regular, white (5A1), sporulation absent; reverse pale yellow (3A3). Colonies on OA researching 37–38 mm diam. after 2 weeks at 25 °C, flattened, barely perceptible growth, not distinguishable colour, sporulation sparse. Exudate and diffusible pigment absent in all culture media tested. Minimum, optimal and maximum temperature of growth on PDA: 10 °C, 25 °C, and 35 °C, respectively. Haemolytic. Casein hydrolyzed without pH change. Not inhibited by cycloheximide. Urease positive. Growth occurs at NaCl 3 % w/w, but not at 10 %w/w. Neither grow on TOTM.
Because the strain FMR 17680 was placed phylogenetically close to Malbranchea filamentosa but in a separate terminal branch, and because both differ morphologically and genotypically, the new species Malbranchea stricta is proposed.
Malbranchea stricta Rodr.-Andr., Stchigel & Cano, sp. nov. Fig. 9. MycoBank MB 835219.
Etymology: Latin stricta, strict, due to the production of the typical reproductive structures of the genus.Diagnosis: Malbranchea stricta is phylogenetically close to M. filamentosa. Also, both species lack of a sexual morph (Sigler et al. 2002). However, M. filamentosa produces more regularly shaped conidia than M. stricta, and forms thick-walled brown setae, structures absent in M. stricta.Type: United States of America: Florida, human nail, 2003, N. Wiederhold (CBS H-24458 – holotype; CBS 146932 = FMR 17680 = UTHSCSA DI18-86 – ex-type cultures; LSU sequence GenBank LR701639).
Description: Vegetative hyphae hyaline, smooth- and thin-walled, straight to sinuous, sparsely branched, 1.5–2.0 μm wide. Fertile hyphae well-developed, arising as lateral branches from the vegetative hyphae, mostly unbranched, right or slightly sinuous, contorted or arcuate at the end, up to 25 μm long, 1.5–2.0 μm wide, or developing at the extremes of the vegetative hyphae, in both cases forming arthroconidia randomly intercalary and terminally. Arthroconidia enteroarthric, hyaline, becoming yellowish with the age, barrel-shaped, “T”-shaped, “Y”-shaped, finger-shaped or irregularly-shaped 2.0–6.0 × 1.0–2.0 μm, with rhexolytic secession. Chlamydospores, racquet hyphae, and sexual morph not observed.
Culture characteristics: Colonies on PYE reaching 32–33 mm diam. after 2 weeks at 25 °C, flattened, velvety, regular margins, furrowed, white (4A1), sporulation sparse; reverse pale orange (5A3). Colonies on PDA reaching 20–21 mm diam. after 2 weeks at 25 °C, slightly elevated, velvety to floccose, regular margins, white (3A1), sporulation abundant; reverse pale yellow (4A3). Colonies on PDA reaching 20–21 mm diam. after 2 weeks at 30 ºC, slightly elevated, velvety to floccose, margins regular, white (3A1), sporulation abundant; reverse yellowish brown (5E8) at centre and greyish yellow (4B5) at the margins. Colonies on OA researching 16–17 mm diam. after 2 weeks at 25 °C, flattened, granulose, white (3A1), margins regular, sporulation sparse. Exudate and diffusible pigment absent. Minimum, optimum and maximum temperature of growth on PDA: 10 °C, 30 °C, and 37 °C, respectively. Colonies haemolytic (on BA), and casein hydrolyzed without pH changes at 25 °C (on BCP-MS-G). Not inhibited by cycloheximide. Urease and esterase tests positive. Growth occurs at NaCl 10 % w/w, but not at 20 % w/w.
Dichotomous key to Malbranchea spp. (adapted from Sigler & Carmichael 1976, Solé et al. 2002, and Hubka et al. 2013).
1a. Homothallic species.......................................................................................................... 2
1b. Heterothallic species....................................................................................................... 13
2a. Peridial appendages longer than 150 μm long................................................................... 3
2b. Peridial appendages shorter or absent...………….………………......……..................... 8
3a. Appendages 350–600 μm in length; diffusible pigment pinkish to reddish; not growing at 35 ºC…............................................................................................................. M. ostraviensis
3b. Those features not combined............................................................................................. 4
4a. Ascospores smooth-walled under bright field microscope.................... M. gymnoascoides
4b. Ascospores reticulate........................................................................................................ 5
5a. Peridial cells short, 4–12 μm in length; peridial projections with truncate ends...................................................................................................................... M. compacta
5b. Peridial cells longer; peridial projections with mostly acute ends.................................... 6
6a. Ascospores usually exceeding 4 μm diameter.......................................... M. californiensis
6b. Ascospores ≤ 4 μm diam................................................................................................... 7
7a. Species growing at 37 °C………………........………………............…........ M. conjugata
7b. No growth at 37 °C........................................................................................... M. umbrina
8a. Asexual morph not produced............................................................ M. pseudoauxarthron
8b. Malbranchea-like asexual morph present…………...……………............................... 9
9a. Ascomata with spine-like peridial projections, 27–40 μm in length................. M. zuffiana
9b. Ascomata without peridial projections……………………….........….……............... 10
10a. Colonies on PDA brown................................................................................... M. kuehnii
10b. Colonies on PDA otherwise.......................................................................................... 11
11a. Peridial hyphae smooth-walled................................................................. M. concentrica
11b. Peridial hyphae strongly ornamented; chlamydospores present…...........…….….....…12
12a. Arthroconidia 2–10 × 2.5–3.5 µm; growing above 30 ºC…............… M. chlamydospora
12b. Arthroconidia 4–24 × 1.0–5.5 µm; not growing above 30 ºC..................... M. longispora
13a. Fertile hyphae arcuate or curved.................................................................................... 14
13b. Fertile hyphae straight to sinuous, branched or not....................................................... 21
14a. Fertile hyphae coiled..................................................................................................... 15
14b. Fertile hyphae curved or arcuate.................................................................................... 16
15a. Thermophilic; conidia 2.5–4.5 μm wide.................................................. M. cinnamomea
15b. Not thermophilic; conidia narrower.............................................................. M. pulchella
16a. Colonies orange............................................................................................................. 17
16b. Colonies different.......................................................................................................... 18
17a. Aleuroconidia laterally or terminally dispersed................................. M. chrysosporoidea
17b. Aleuroconidia absent.................................................................................. M. aurantiaca
18a. Colonies golden yellow, exudate brown, diffusible pigment yellow......... M. graminicola
18b. Features are not combined.............................................................................................19
19a. Sexual morph produced by in vitro mating of compatible strains................. M. albolutea
19b. Sexual morph not formed.............................................................................................. 20
20a. Thick-walled brown setae produced on OA from the vegetative mycelium.......................................................................................................... M. filamentosa
20b. Setae not produced........................................................................................... M. arcuata
21a. Fertile hyphae unbranched or scarcely branched........................................................... 22
21b. Fertile hyphae branched................................................................................................ 23
22a. Arthroconidia cylindrical; becoming many septate with the age............. M. multiseptata
22b. Arthroconidia barrel-shaped, “T”-shaped, “Y”-shaped, finger-shaped or more irregular; vegetative hyphae regularly septate........................................................................... M. stricta
23a. Fertile hyphae branching acutely, displaying a tree-like appearance........... M. dendritica
23b. Fertile hyphae branching pattern otherwise................................................................... 24
24a. Fertile hyphae repeatedly branched, in dense tufts.................................... M. flocciformis
24b. Fertile hyphae more restrictedly branched.....................................................................25
25a. Colonies buff or tan.............................................................................................. M. fulva
25b. Colonies lemon yellow......................................................................................... M. flava
Despite the strain FMR 17684 being placed phylogenetically into the Onygenaceae, is paraphyletic and distant from the other members of the family, therefore this fungus is proposed as the type species of the new genus Pseudomalbranchea.
Pseudomalbranchea Rodr.-Andr., Cano & Stchigel, gen. nov. MycoBank MB 835220.
Etymology: Because the morphological similarity with Malbranchea.
Description: Mycelium sparse, composed of hyaline, smooth- and thin-walled septate hyphae. Asexual morph consisting of mostly enteroarthric -occasionally holoarthric- conidia, intercalary disposed along unbranched vegetative hyphae, solitary or in short chains, with rhexolytic or rarely schizolysic secession. Arthroconidia one-celled, hyaline, smooth- and thick-walled, cylindrical but becoming globose with the age. Chlamydospores, racquet hyphae and sexual morph not observed.
Type species: Pseudomalbranchea gemmata Rodr.-Andr., Cano & Stchigel. MycoBank MB 835221.
Pseudomalbranchea gemmata Rodr.-Andr., Cano & Stchigel, sp. nov. Fig. 10. MycoBank MB 835221.
Etymology: From the Latin gemmatum, jewelled, because the swollen conidia disposed in chains.
Diagnosis: Pseudomalbranchea gemmata is phylogenetically close to Uncinocarpus reesii and Amauroascus volatilis-patellis. However, it does not produce a sexual morph and it differs from U. reessi and A. volatilis-patellis by the production of longer arthroconidia (4.0–11.0 × 2.0–3.5 μm in P. gemmata vs. 3.5–6.0 × 2.5–3 μm in U. reessi, and 4.0–5.4 × 2.0–3.0 in A. volatilis-patellis; Orr & Kuehn 1972, Sigler & Carmichael 1976, Currah 1985). As well as A. volatilis-patellis, P. gemmata lacks appendages, which are present and similar to the asexual morph in U. reessi (Currah 1985).Type: United States of America: Florida, from human’s bronchial washing, 2014, N. Wiederhold (CBS H-24459 – holotype, CBS 146933 = FMR 17684 = UTHSCSA DI18-90 – ex-type cultures; LSU sequence GenBank LR701762).Description: Mycelium sparse, composed of hyaline, smooth- and thin-walled, sparsely septate hyphae, 1.0–2.0 μm wide. Conidia enteroarthric (occasionally holoarthric), intercalary disposed along unbranched vegetative hyphae, one-celled, solitary or in short chains of up to 7, one-celled, hyaline, smooth- and thick-walled, cylindrical but becoming globose with the age, 4.0–11.0 × 2.0–3.5 μm, liberated from the fertile hyphae by rhexolysis (rarely by schizolysis). Chlamydospores, racquet hyphae and sexual morph not observed.
Culture characteristics: Colonies on PYE reaching 22–23 mm diam. after 2 weeks at 25 °C, slightly elevated, velvety, margins regular, pale yellow (3A3), sporulation sparse; reverse brown (6E6). Colonies on PDA reaching 24–25 mm diam. after 2 weeks at 25 °C, slightly elevated, velvety, margins regular, pale yellow (3A3), sporulation sparse; reverse light yellow (4A5). Colonies on PDA reaching 25–26 mm diam. after 2 weeks at 30 ºC, flattened, radially folded, velvety, margins regular, pale yellow (3A3), sporulation sparse; reverse light yellow (4A5). Colonies on OA reaching 28–29 mm diam. after 2 weeks at 25 °C, flattened, velvety to granulose, irregular margins, white (6A1), sporulation sparse. Exudate and diffusible pigment lacking. Minimum, optimum and maximum temperature of growth on PDA: 10 °C, 30 °C, and 37 °C, respectively. Colonies haemolytic, casein not hydrolyzed. The fungus was not inhibited by cycloheximide. Urease and esterase tests positive. Growth occurs at NaCl 3 % w/w, but not higher concentration.
Because the strains FMR 17686 and FMR 17696 were placed together in a terminal branch close related to the ex-type strain of M. gypsea into the Spiromastigaceae clade (Fig. 2), M. gypsea is renamed as Spiromastigoides gypsea, and the former strains are proposed as belonging to the new species Spiromastigoides geomyces.
Spiromastigoides geomycoides Stchigel, Rodr.-Andr. & Cano, sp. nov. Fig. 11. MycoBank MB 835222.
Etymology:Because produce conidiophores morphologically similar to those of the genus Geomyces.Diagnosis: Spiromastigoides geomycoides is phylogenetically close to S. gypsea. However, S. geomycoides produces smaller conidia (1.5–2.5 × 1.0–2.0 μm) than S. gypsea [(2.5)3–6(9) × 2–2.5 μm] (Sigler & Carmichael 1976). Also, S. geomycoides grows faster than S. gypsea on PYE at 35 ºC.Type: United States of America: Illinois, from a human foot skin, 2014, N. Wiederhold (CBS H-24460 – holotype, CBS 146934 = FMR 17696 = UTHSCSA DI18-102 – ex-type cultures; LSU sequence GenBank LR701768).Description: Mycelium abundant, composed of hyaline, smooth- and thin-walled, septate, branched, 1.0–2.0 μm wide hyphae, septa thickened with age. Fertile hyphae arising as lateral branches, straight or slightly curved, unbranched or, rarely, with a branching pattern similar to that of the conidiophores of Geomyces, septate, hyaline, smooth- and thin-walled, producing intercalary and terminally arthroconidia separated by 1-2 empty intermediary cells. Conidia enteroarthic, unicellular, hyaline, mostly barrel-shaped, less frequently “T”-shaped or cylindrical, 1.5–2.5 × 1.0–2.0 μm, rhexolytic dehiscence. Chlamydospores, racquet hyphae and sexual morph not observed.
Culture characteristics: Colonies on PYE reaching 24–25 mm diam. after 2 weeks at 25 °C, flattened, velvety, furrowed, regular margins, white (4A1), abundant sporulation; reverse, pale orange (5A3). Colonies on PDA reaching 26–27 mm diam. after 2 weeks at 25 °C, flattened, velvety, regular margins, white (4A1), abundant sporulation; reverse, yellowish white (4A2). Colonies on PDA reaching more than 90 mm diam. after 2 weeks at 30 ºC, flattened, velvety, regular margins, yellowish white (4A2), sporulation absent; reverse, pale yellow (4A3). Colonies on OA researching 20–21 mm diam. after 2 weeks at 25 °C, flattened, granulose, regular margins, white (4A1), abundant sporulation. Exudate and diffusible pigment absent in all culture media tested. Minimum, optimum and maximum temperature of growth on PDA: 5 °C, 30 °C, and 37 °C, respectively. Colonies non-haemolytic. Casein not hydrolyzed. Resistent to cycloheximide. Urease negative and esterase positive. Growth occurs at NaCl 10 % w/w, but not at 20 % w/w.
Other specimens examined: United States of America: Minnesota, from blood, 2009, N. Wiederhold (FMR 17686).
Spiromastigoides gypsea (Sigler & Carmichael) Stchigel, Rodr.-Andr. & Cano, comb. nov. MycoBank MB 835228.
Basionym: Malbranchea gypsea Sigler & Carmichael, Mycotaxon 4: 455 (1976). MycoBank MB 317129.
Description (adapted from the original work): Arthroconidia produced intercalary or terminally along of straight primary hyphae, or on short or long lateral branches, separated each one by one or more alternate empty cells, or, rarely, formed immediately adjacent to each other. Arthroconidia unicellular, hyaline, smooth- and thin-walled, cylindrical or slightly barrel-shaped, (2.5) 3–6 (9) × 2–2.5 μm, slightly broader than the interconnecting cells. No sexual morph obtained by matting. Colonies on PYE reaching 17–39 mm after three weeks at room temperature, chalky white to creamy white, downy to velvety, slightly raised, surface folded to convoluted, umbonated at centre, reverse buff. Optimum temperature of growth 25–30 ºC. Maximum temperature of growth 37 ºC (but strain depending).
Dichotomous key to Spiromastigoides spp. (adapted from Hirooka et al. 2016).
1a. Homothallic....................................................................................................................... 2
1b. Heterothallic..................................................................................................................... 6
2a. Ascospores globose to subglobose, reticulate............................................ S. sphaerospora
2b. Ascospores oblate, equatorial thickening present or not................................................... 3
3a. Ascospores with equatorial thickening.............................................................................. 4
3b. Ascospores without such equatorial thickening................................................................ 5
4a. Ascomata appendages straight or slightly undulate; ascospores yellow, smooth-walled, pitted under SEM................................................................................................. S. alatospora
4b. Ascomata appendages slightly undulate or wavy; ascospores pale yellowish brown, minutely punctate under SEM.......................................................................... S. saturnispora
5a. Ascospores punctate, sometimes with a few fine grooves in the polar region, 2.5–2.9 × 2.0–2.5 μm.............................................................................................................. S. warcupii
5b. Ascospores lens-shaped, regularly pitted, 3.0 × 2.0 μm.................................. S. sugiyamae
6a. Asexual morph chrysosporium-like; sterile ascomata present.......................... S. asexualis
6b. Asexual morph not so........................................................................................................ 7
7a. Asexual morph malbranchea-like...................................................................................... 8
7b. Asexual morph more complex......................................................................................... 11
8a. Fertile hyphae straight, branched.......................................................................... S. gypsea
8b. Fertile hyphae curved........................................................................................................ 9
9a. Fertile hyphae successively branched to form sporodochia-like structures........... S. albida
9b. Fertile hyphae unbranched or scarcely branched............................................................. 10
10a. Fertile hyphae unbranched or sparsely branched, curved, up to 28 μm long; chlamydospores present............................................................................................ S. curvata
10b. Fertile hyphae unbranched, slightly curved, up to 15 μm long; chlamydospores absent....................................................................................................................... S. minimus
11a. Conidiophores unbranched or scarcely branched..................................... S. geomycoides
11b. Conidiophores branched several times.......................................................................... 12
12a. Conidiophores up to 300 μm in length, verticillate........................................ S. kosraensis
12b. Conidiophores 100–150 μm in length, with pyramidal or bush-like branching............ 13
13a. Conidiophores up to 150 μm long, with pyramidal branching.................... S. pyramidalis
13b. Conidiophores up to 100 μm long, with bush-like branching.............................. S. frutex
In vitro antifungal susceptibility testing
The results of the antifungal susceptibility test are summarized in Table 2. In general, the echinocandins (AFG, CFG and MFG) displayed the most potent in vitro antifungal activity, but TRB and PSC also demonstrated a good activity against these fungi. In contrast, limited to no inhibition of growth was observed with AMB, FLC, ITC and 5-FC. Antifungal activity was evaluated against all strains with the exception of FMR 17691, due to the scarce production of conidia and because this strain does not grow in RPMI medium, even after two weeks of incubation.