Capronia mansonii

Capronia mansonii is a type of black yeast that was first discovered from an isolated strain in 1968.[2][3] The fungus was originally described from a strain in vitro found in Norway by Marie Beatrice Schol-Schwarz on an aspen tree, and it has not yet been described in situ.[3][5] This fungus was the first species in Herpotrichiellaceae discovered to create ascomata in an isolated culture.[4] It is one of the only five species out of thirty Capronia species that has successfully produced ascomata in vitro.[5] The basionym for this species is Dictyotrichiella mansonii.[6] Its anamorph is thought to be Exophiala mansonii but uncertainty and discourse remains.[3][7] The original anamorph was first thought to be Rhinocladiella atrovirens and then Exophiala castellanii [8][7] An analysis of rRNA gene sequences concluded that C. mansonii is the same biological species as E. castellanii.[7] Capronia mansonii is often misidentified as its sister species Capronia munkii but can be differentiated by its larger and thicker cell walls and more frequent ascospores that transversely septate.[3] It is also differentiated from its anamorph because it lacks conidia, slimy colonies, and aerial hyphae.[9]

This fungus is a teleomorph or sexual form that is formed in vitro. This species has yet to be described in situ.[5] The fungus is thought to be closely related to Exophiala dermatitidis, and is often hypothesized in literature to be the teleomorph of E. dermatitidis.[3] The fungus is a part of the ascomycota phylum, also commonly defined as sac fungi. This phylum is often defined by its possession of asci, a microscope sexual structure that produces non-motile spores called ascospores. The asci of C. mansonii produce 8 ascospores upon germination.[3] These ascospores begin with a glassy transparent appearance and then progress to a more grey-yellow, olive, and finally brown colour.[3][6] These ascospores have 4–5 transverse thick-walled septa and 1 incomplete longitudinal septum.[6] The spores have been described in literature as not tight at the septa.[3] Juvenile asci have thicker, longer, and more lightly coloured ascus walls whereas as fully matured asci form thinner dark brown walls that are filled with ascospores.[3] The ascomatal wall itself can range from a brown-yellow to a light brown colour which is commonly seen in other black yeasts.[3]

This mesophilic fungus has been successfully cultured by Untereiner at room temperature ranging from 20–25 °C.[5][10] C. mansonii has also been observed in a yeast budding form.[2] This fungus has a homothallic breeding system indicating that it does not need a partner to sexually reproduce.[5] The ascospores of this fungus have been described to germinate within 12 hours on Oatmeal Agar.[5][4] They appear slimy and resemble yeast within 48 hours, reaching full maturity at 16 weeks.[5] The ascomata that have been grown in lab have been shown to fully mature and develop septae but are unable to produce asci and ascospores.[5] Artificial daylight is thought to be the limiting factor that prevents the production of asci.[10] Further replications of the above experiments revealed that the structure formed may actually be a pseudothecium, an ascocarp that resembles a ascocarp but whose asci do not organize into a hymenium.[10] The pseudothecia grew in abundance and also failed to produce ascospores.[10]

Members of the Capronia family are described as saprotrophic meaning they get their nutrients from decaying matter.[10] Strains of this fungus have been found on various plant hosts, particularly on their leaves.[5] They are regularly found on other decaying ascomycota and basidiomycota in the Netherlands, particularly on the wood of Populus tremula.[6][11] The holotype was discovered on the stems of a Lupinus polyphyllus by Schol-Schwarz in 1968.[6][11] This fungus has occasionally been found on fresh sausages consisting of pork, beef, or mixed meats.[2] They remain unstable on meat and are unable to persist for more than three days in the presence of other lactic acid bacteria.[2]