Pseudallescheria Negr. & I. Fisch., Revista Inst. Bacteriol.

Yang, Erfu, Karunarathna, Samantha C., Shao, Shicheng, Han, Lisu, Samarakoon, Milan C., Elgorban, Abdallah M., Chiu, Chuni, Tibpromma, Saowaluck & Promputtha, Itthayakorn, 2025, Additions to Termitomyces aurantiacus growing termite comb-associated fungi, Phytotaxa 690 (2), pp. 212-230 : 223-225

Pseudallescheria Negr. & I. Fisch., Revista Inst. Bacteriol. 'Dr. Carlos G. Malbrán' 12(no. 201): 5–9 (1944)

Index Fungorum number: IF4403

Type species: Pseudallescheria shearii Negroni & I. Fisch. 1944

Notes: Pseudallescheria ( Microascaceae ) are usually polymorphic; the sexual state is defined by closed, globose ascomata (cleistothecia) surrounded by a peridium of epidermoid texture, the asci are widely club-shaped or spherical and ephemeral, containing ellipsoidal or fusiform ascospores that range from hyaline to pale brown ( Gilgado et al. 2007). In addition, Pseudallescheria can exhibit two types of asexual forms. Scedosporium is identified by cylindrical, hyaline conidiogenous cells developed from undifferentiated hyphae, producing obovoidal and sticky conidia ( Gilgado et al. 2007); Graphium is identified by substantial, synnemaous, upright hyphal bundles culminating in a dense cluster of conidiogenous cells and conidia are produced from short extensions of these cells with annellidic development ( Abrantes et al. 2021). Sometimes, three morphs can be observed in the same culture. They are associated with diverse ecological niches, primarily including soils and streams polluted with aliphatic and aromatic chemicals, cattle dung, and sewage ( Abrantes et al. 2021). More importantly, Scedosporium species such as S. apiospermum , S. aurantiacum , S. prolificans , and Pseudallescheria boydii are common human pathogens, Scedosporium infections result in many clinical manifestations, including osteomyelitis, keratitis, lymphocutaneous infection, and sinusitis ( Lu et al. 2011, Abrantes et al. 2021). In addition, the phylogram of Pseudallescheria is presented in Figure 9 .

Pseudallescheria angusta (Malloch & Cain) McGinnis, A.A. Padhye & Ajello [as 'angustum'], Mycotaxon 14(1): 97 (1982)

Index Fungorum number: IF110949

Harboured in termite fungus gardens. Sexual morph: Ascomata 75–115 × 70–100 µm (x = 93 × 86 µm, n = 20), pale brown to black brown, globose, superficial, solitary. Peridium consists of brown cell that are hypha-like and amorphous textura epidermoidea. Asci 11–18 × 7–12 µm (x = 14 × 9 µm, n = 20), globose to subglobose, hyaline, thin-walled, eight-spored, short pedicellate. Ascospores 5–6.5 × 3–4 µm (x = 5.5 × 3.5 µm, n = 20), subglobose, one-celled, hyaline to yellow-brown on maturity, thick-walled, smooth, with obtuse ends, often containing 2–3 distinct oil droplets. Asexual morph: Hyphae 3–5 µm wide, branched, hyaline to pale brown, with thick walls and septa. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 5–9 × 3–5 µm (x = 6.5 × 4 µm, n = 20), solitary, holoblastic, cylindrical, straight, hyphae-like, emerging terminally or laterally from hypha, smooth-walled. Conidia 5–8.5 × 3–5 µm (x = 7 × 4 µm, n = 20), ovoid, ellipsoidal, thick-walled, pale brown to dark brown, often with two distinct oil droplets, rounded at the end, flat at base. Synnemata not observed.

Substrata: Sewage half digestion tank, soil ( Lu et al. 2011); termite fungus gardens (this study).

Distribution: The USA, Zaire ( Lu et al. 2011); China (this study).

Culture characteristics: Colonies on PDA exhibit moderate growth, reaching approximately 30 mm in diameter after one month. Obverse: flat or effuse, circular, pale brown; Reverse: pale brown. In PDA, no pigments were observed.

Material examined: China, Yunnan Province, Xishuangbanna Tropical Botanical Garden, 20 July 2022, E.F. Yang, C1 ( HKAS 129050) living culture KUNCC 22-12515, KUNCC 23-13359. GenBank numbers, KUNCC 22-12515 = LSU: PP911541, ITS: PP915827, tub2: PP918926. KUNCC 23-13359 = LSU: PP911542, ITS: PP915828, tub2: PP918927.

Notes: Our isolates produced both asexual morph and sexual morph in PDA media, and the morphological characteristics match the concept of Scedosporium and Pseudallescheria ( Figure 10 ), producing hyaline asci filled with eight fusiform, one-celled, pale brown ascospores and enteroblastic, one-celled, solitary, hyaline to sub-hyaline, ovoid to subglobose conidia ( De Hoog et al. 2000, Lu et al. 2011, Abrantes et al. 2021). According to results from BLASTn searches, ITS and LSU genes of our isolates share 98–99% base pair similarities with Pseudallescheria ellipsoidea ( LMA 40407486), Pseudallescheria angusta ( CBS 254.72) and Scedosporium boydii ( CBS:127829, DMic 083389, DMic 165279); while the tub2 gene only showed 98–99% similarities with Pseudallescheria angusta ( CBS 116894, CBS 108.54, CBS 106.53). In addition, the phylogram also indicated that our isolates ( KUNCC 22-12515, 23-13359) were specifically placed in the clade of Pseudallescheria angusta ( Figure 9 ). Therefore, we illustrate a new collection record of P. angusta from termite fungus gardens.

Figures

FIGURE 9. Phylogram of Scedosporium constructed using maximum likelihood analysis, based on a combined ITS and tub2 sequence dataset.The analysis encompassed 52 strains and a total of 1082 characters (ITS: 1–557 bp, tub2: 558–1082 bp). Newly introduced species are highlighted in red, and the type strains are indicated in bold. Bootstrap values equal to or higher than 60% (ML, left) and Bayesian posterior probabilities equal to or higher than 0.95 (BI, right) are indicated at the nodes, while hyphens (-) denote values below these thresholds for ML/BI.

FIGURE 10. Scedosporium angusta (HKAS129050): (a) Colonies in PDA, (b–d) Ascomata on PDA, (e) Ascomata and ascomatal wall, (f) Asci, (g) Asci stained by congo red dye, (h,i) Mycelium on PDA, (j) Conidiogenous cells connected with developing conidia, (k) Ascospores, (l) Conidia.