Cyllamyces aberensis gen.nov sp.nov., a new anaerobic gut fungus with branched sporangiophores isolated from cattle

A new genus of the anaerobic gut fungi (Neocallimastigales), Cyllamyces abe rensis gen.nov. sp.nov., with bulbous holdfast, branched sporangiophores an d limited polycentric thallus development is described. The fungus was isol ated from fresh cattle faeces. Free-swimming zoospores were spherical, unin ucleate, and uniflagellate. After encystment, zoospores germinated and gave rise to a single, bulbous holdfast. One or several branched sporangiophore s were produced from different locations on the holdfast, each bearing seve ral spherical sporangia. DAPI staining of thalli indicated that nuclei were present in the holdfast, sporangiophores, and sporangia. As many as 12 spo rangia were observed per thallus on up to 5 sporangiophores, with zoosporog enesis beginning 16-18 h after encystment. Zoospore ultrastructure was exam ined by transmission electron microscopy and found to be similar to that re ported for other anaerobic chytrid fungi. Organelles were evenly distribute d throughout the cell, except for the posteriorly attached flagellum and as sociated attachment apparatus, the hydrogenosomes, which were mainly situat ed in the posterior parts of the cell and a posteriorly directed, beak-shap ed nucleus. Limited polycentric thallus development (including branched spo rangiophores), the possession of a single bulbous holdfast and the absence of rhizoids were stable features of this fungus that distinguished it from the other five genera of gut fungi. Therefore, we have used these character istics to assign the fungus to a new genus, Cyllamyces, with the specific n ame C. aberensis.