Piromyces finnis O’Malley, Haitjema & Gilmore, sp. nov.
Index Fungorum number: IF 551677, Facesoffungi number: FoF 02062, Fig. 3
Etymology — ^‘Piromyces of Finn^/^Finn’s Piromyces.’^The specific epithet refers to the animal host, a horse named BHuckleberry Finn^, from which the fungus was isolated.
Holotype — Piromyces sp. finn (O’Malley Lab, University of California, Santa Barbara, NCBI Taxon ID: 1577477), JMRC:SF:12177.
An obligate anaerobic fungus isolated in 2011 at MIT from the feaces of the award-wining show jumping horse Huckleberry Finn, owned by Susan Huyett of Concord, MA. The species is monocentric and has a determinate (finite) life cycle. The fungus exhibits endogenous zoosporangial development (i.e., the encysted zoospore retains the nucleus). The encysted zoospore geminates to form a rhizoidal system and a single oval or club shaped zoosporangium(≥ 100μm long and 30 – 60 μm wide), which onmaturity liberates ≥ 100 zoospores. The rhizoidal system is devoid of nuclei (as seen under DAPI staining) and is highly branched and tapering. The zoosporangium is typically attached to the rhizoidal system via one main rhizoid or sporangiophore. A septum is often visible inmature zoosporangia, separating the zoosporangium from the sporangiophore. Free swimming zoospores are typically sphearical (ca. 10 μm diam.) and the species is characterized by the presence of a single posteriorly directed flagella that is in length up to 3 – fold the diam. of the zoospore. When swimming the flagella beats posteriorly and thus propel the zoospore forward in a spiral or helical motion.
The reference culture is maintained by continually passage at the University of California, Santa Barbara (JMRC:SF:12177, holotype), and under cryopreservation in repositories at the University of Jena and Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany (Jena Microbial Resource Col l e c t ion JMRC:SF:012177, ex-type). Fixed glutaraldehyde preparations are also kept by the O’Malley Lab.
The internal transcribed spacer regions of the ribosomal RNA were amplified with primers JB206/JB205 (Tuckwell et al. 2005). Phylogenetic analysis of the ITS1 regions of several cultured anaerobic fungal specimens spanning all eight known genera and partial 28 s reads, firmly place Finn within the Piromyces as a distinct, previously unclassified species (Figs. 1, and 2). The ~56 Mbp genome has been sequenced by the US Department of Energy’s Joint Genome Institute (JGI). The genome will be available at Mycocosm in 2016 (http://genome.jgi.doe.gov/Pirfi3/Pirfi3.home.html).

Fig. 1 Molecular phylogeny generated by maximum likelihood analysis of ITS1 sequence data from the Neocallimastigomycota. Representative species from all known eight genera (indicated) are shown. Bootstrap values above 50 % are indicated above each branch. Ex-types (reference strains) are bolded and new isolates are indicated in blue.

Fig. 2 Molecular phylogeny generated by maximum likelihood analysis of partial large subunit (28S) ribosomal DNA sequence data from the Neocallimastigomycota. Bootstrap values above 50 % are indicated above each branch. New isolates are indicated in with a filled shape.

Fig. 3 Piromyces finnis (holotype) a Multiple sporangia of P. finnis exhibiting a range of morphological features from club-like to ovoid b A group of young sporangia, not much larger than zoospores beginning to form c Mature zoosporangia d Several zoospores of P. finnis.