Tropis tropicalis is part of the family Hymenochaetaceae, and was recently renamed to Tropicoporus tropicalis from Inonotus tropicalis, which is part of the Inonotus clade B.[1] Tropicoporus tropicalis is a wood-decaying basidiomycetes that rarely causes disease in animals and human, and is commonly found in humid climate such as Brazil.[2][3][4][5][6] In its natural environment, the fungus is associated with white rot woody angiosperms, and has its annual fruiting body on tree trunks and branches.[3] Tropicoporus tropicalis has two kinds of hyphae (a dimitic hyphal system), generative and skeletal, that lack clamp connections.[2][3][7][8]
Taxonomy, classification, and phylogeny
The earliest record of Tropicoporus tropicalis is by the name Poria rickii, which is then modified into Phellinus rickii, and then renamed to Phellinus tropicalis.[8] However, it is later suggested that Phellinus tropicalis should belong to one of the Inonotus sensu stricto clade after phylogenetic analysis of the fungus's rDNA nuclear LSU sequence.[9] The name Inonotus rickii was also used to describe this fungus, and it is also a species of Inonotus sensu stricto.[10]
The genus Inonotus contains at least three clades (A, B, and C), and Clade B and C have species from the Inonotus linteus complex, which was transferred from Inonotus sensu stricto.[1][7] However, the Inonotus linteus complex is later divided into Sanghuangporus and Tropicoporus.[1] After the transfer from Inonotus sensu stricto to Inonotus linteus, and then to Tropicoporus, the fungus is currently named as Tropicoporus tropicalis.[1]
Description and characteristics
Tropicoporus tropicalis is a fungus with the growth characteristics of being appressed, short-downy, homogeneous, adherent, even margins, indistinct, and odourless.[8] It is also woolly and yellowish-orange colonies,[2] with annual fruiting bodies and dimitic hyphal system,[9] which refers to the appearance of two kinds of hyphae: generative (2.5 – 4 ɥm in diameter, thin-walled, simple-septate, and pale yellowish brown), and skeletal (3.5 – 4.5 ɥm in diameter, thick-walled, infrequently simple-septate, and dull yellowish brown).[3][7][8] Moreover, the fungus lacks setal hyphae and clamp connections in its hyphae, which is either thin or thick walled.[2][7] However, it has numerous reddish brown Hymenial setae that has a maximum length of 25 ɥm,[7][10] and has dull brown pores that becomes whiter near the margin.[8][10] The Basidiocarp of Tropicoporus tropicalis is annual, resupinate, and hyaline.[1][7] The abundant fungal spores are coloured yellowish to ochraceous, and shaped ovoid to broadly ellipsoid and smooth when mature.[10] Both the spores (7 - 9 per mm) and the basidiospores are small, with basidiospores having more than 3.5 um wide when it is ellipsoid, and are less than 3.5 um wide when it is sub-globose.[1][7]
Physiology
The fungus grows:
- Moderately rapid in MEA (Malt Extract Agar)[8]
- In 0.05% cycloheximide[2]
The mat diameter of the fungus depends on temperature, but the optimal growth temperature is around 36 °C, and the maximum temperature without growth (not killed) is 44 °C.[8] Even though all parts of the fungus could be darkened by 2% KOH, only the hyphae can be stained by phloxine, a reddish dye.[8] Furthermore, Tropicoporus tropicalis is also found to be highly resistant to caspofungin and posaconazole, two different anti-fungal compounds.[2]
Ecology and habitat
Tropicoporus tropicalis is a poroid wood-decaying basidiomycete[3][4] that is usually associated with white rot woody angiosperms,[2] grow on deciduous wood,[5] and have fruiting body on infected tree trunks and branches.[3] It is mainly found in the tropical zone[1] and humid climate,[5] such as Brazil; but is present in Mississippi, Florida, Georgia, Jamaica, Guadeloupe, Costa Rica, Colombia, East Africa, and Malaya, Johore, and Mawaii Malaysia.[6]
Diseases
Tropicoporus tropicalis rarely causes diseases in animals and human.[2] However, it is an opportunistic pathogen that has the potential to induce allergic and invasive diseases in mammals.[2]
Animal
The fungus has been recorded to cause fungal pericardial effusion and myocarditis in a French bulldog, that was under immunosuppressive therapy (species was non-pigmented, and has indication of a hyalohyphomycosis infection);[4] and induced a granulomatous mediastinal mass in an immunocompromised Irish Wolfhound dog.[11]
Human
The first association of an invasive infection on human occurred on a patient with chronic granulomatous disease.[6][12] In addition, two similar chronic granulomatous disease cases of I. tropicalis infection were later found in immunodeficient children and adults that had caused osteomyelitis.[5]