Anaeromyces robustus O’Malley, Theodorou & Henske, sp. nov.
Index Fungorum number: IF 551676, Facesoffungi number: FoF 02060, Fig. 3
Etymology – The specific epithet refers to the physical similarities between some fungal zoosporangia and the tails of gray whales (Eschrichtius robustus) that travel the Californian coast near where the fungus was isolated.
Holotype – Anaeromyces sp. S4 (O’Malley Lab, University of California, Santa Barbara, NCBI Taxon ID: 1642509), JMRC:SF:12178.

An obligate anaerobic fungus isolated from the feces of a sheep (Ovisaries) at the Santa Barabara Zoo (www.sbzoo.org) in 2013. The species is polycentric, producing many zoosporangia per fungal thallus and therefore has an indeterminate (infinite) life cycle. The fungus exhibits exogenous zoosporangial development (i.e., the encysted zoospore does not retain the nucleus, which can migrate and by mitosis populate the developing zoosporangium and the rhizomycelium). The zoosporangia are typically club-shaped (≥50 μm long × 30 μm wide at their widest point). Occasionally they fuse to form a shape like a whale’s tail. Upon maturity, each zoosporangium can liberate ≥ 60 zoospores. The rhizomycelium does contain nuclei (as seen under DAPI staining) and is highly branched and tapering. The zoosporangium is typically attached to the rhizomyceliumvia one or several main rhizoids and is capable of vegetative reproduction by fragmentation. Free swimming zoospores are typically sphearical (ca. 10 μm diam.) and the species is characterized by the presence of several posteriorly directed flagella that are in length up to 3 – fold the diam. of the zoospore. When swimming the flagella beat together as if they were a single flagellum and thus propel the zoospore forward in a spiral or helical motion.

The reference culture is maintained by continual passage at the University of California, Santa Barbara (S4, JMRC:SF:12178, holotype), and under cryopreservation in repositories at the O’Malley Lab, University of California, Santa Barbara, and University of Jena and Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany (Jena Microbial Resource Collection JMRC: SF: 012178 – 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 8 known genera, firmly place S4 within Anaeromyces as a distinct, previously unclassified species comparable in age to the type culture A. mucronatus JF1 (Fig. 1). The partial 28 s rRNA sequence of A. robustus, however, appears as a unique outgroup, perhaps due to its incompleteness (Fig. 2). The ~72 Mbp genome has been sequenced by the US Department of Energy’s Joint Genome Institute (JGI). The genome will be made available at Mycocosm in 2016 (http://genome.jgi.doe.gov/Anasp1/Anasp1.home.html) and aid in the discovery of novel biomass degrading enzymes that may be engineered or heterologously expressed for the production of lignocellulosic biofuels and other value added chemicals. Furthermore, the genome will enable future – OMICs based characterization of these organisms, including insight into their unique organelles and biomass-degrading enzyme complexes.

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 Aneromyces robustus (holotype) a Multiple sporangia of A. robustus displaying a range of morphologies b A whale-tale shaped sporangia, which inspired the name of this species, with a single zoospore c A zoospore with multiple flagella visible d Navajo-Churro sheep host from which the species was isolated e Multiple sporangia demonstrating club-like morphology, with several sharing the same mycelial structure.