Paucimyces was the 20th genus to be discovered, and the fourth polycentric anaerobic fungal genus to be described. This genus forms polycentric thalli, filamentous rhizomycelia, and monoflagellated zoospores.
The genus Paucimyces was formally classified by Hanafy et al (2021), and was isolated from the faeces of a wild blackbuck (Indian Antelope). The genus name is derived from the Latin word for “few”, which refers to the relatively limited distribution of the genus. The type species is P. polynucleatus. The species name refers to its polynucleated filamentous rhizomycelium. The type strain is BB3. To date, no other species have been described for the Paucimyces genus.
Paucimyces is the first cultured representative of clade RH5, which was first discovered in a previous culture independent survey (Hanafy et al, 2020). This study has revealed that members of the genus Paucimyces are not widely distributed in nature, and were identified only in sheep samples, suggesting possible genus preference for the ovine alimentary tract.
Within the family Neocallimastigaceae, Paucimyces forms a distinct branch basal to the clade that includes Pecoramyces, Orpinomyces, Neocallimastix, Feramyces, Ghazallomyces and Aestipascuomyces (when using LSU as a taxonomic marker).
Images courtesy of Dr Radwa Hanafy
Images are shown above of the Paucimyces polynucleatus type strain BB3. In liquid media, Paucimyces produces a loose thin white biofilm-like fungal growth (Figure 1). On agar roll tubes, it produces medium sized white compact circular uniform colonies (Figure 2). Microscopically, Paucimyces produces mainly monoflagellated zoospores (Image 3), although biflagellated zoospores can ocassionally be observed (Image 4). The genus has a polycentric thallus with filamentous nucleated rhizomycelia (Figure 5). Spherical vesicles (SV) are developed at the hyphal tips, and multiple sporangia are developed directly on the spherical vesicles (Image 6) or at the end of sporangiophores (Sp) (Image 7). Old cultures lose the abilty to produce sporangia, and are only capable of undergoing the initial stages of sporangiophore formation (Image 8, arrows).
No sequenced genome or transcriptomes are currently available for Paucimyces. For Paucimyces polynucleatus culture strain BB3 that is pictured above, sequence information is available in the NCBI database (accession number MW694896 for partial 18S, ITS1, 5.8S, ITS2 and partial 28S).