Mortierella exigua

Figure 1. Concentric growth of Mortierella exigua.

Zygomycetes are an interesting group of fungi that have recently undergone a large reclassification (Spatafora et al. 2016). They do not produce large fruiting bodies, so they are often overlooked by your average mushroom hunter. However, zygomycetes like the Mortierella spp. (Figure 1) are often well represented in soil assays of fungal diversity. They also grow on a wide variety of other substrates: dead wood, leaves, and even other fungi! Recently, we reported on an interesting fungi known as Daldinia concentrica – a perennial fungus that can often be mistaken for a piece of charcoal (a mistake which we almost made ourselves). On another isolate of Daldinia concentrica from Baker Woodlot at MSU we noticed a strange white dusting (Figure 2 – white dusting surrounding the chipped away region in the center of the D. concentrica fruiting body) that piqued our interests. Unsure of what it could be, we plated it on water agar just to see if anything would grow. Lo and behold, about one week later there were signs of life – more than we had hoped in fact.

Figure 2. Daldinia concentria next to the water agar plate where small scrapings from the white-powdery region were plated.

We noticed a number of nematodes swimming about, and some fungi are known to be nematophagous (nematode consumers) so we waited a few more days to see if we saw any signs of nematode trapping structures though none were seen. We did, however, see what appeared to be many globose, terminal spores (not pictured). At this time the unknown zygomycete was subcultured on complete media and allowed to grow for several days, after which time it produced the beautiful concentric growth form you see in Figure 1 – this is a key identifying feature of some zygomycetes, including Mortierella spp. Mortierella spp. are difficult to key out morphologically, so we decided to identify these through DNA sequencing. When the sequencing results came back, based on ITS1, they identified our isolate as Mortierella exigua Linnem. 1941. The ITS1 sequences were submitted to GenBank and at the time of this writing are awaiting review.

Literature Cited:

Spatafora JW, Stajich JE, Benny GL, Smith ME, Berbee ML, Corradi N, Grigoriev I, James TY, Donnell KO, Roberson RW (2016) A phylum-level phylogenetic classification of zygomycete fungi based on genome-scale data. Mycologia 108: 1028–1046

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