JF2 05-3F “Dopey” plate image. This fungus was grown on an MEA plate for 10 days when this photo was taken. Its highly melanized cell wall is easily observed by the dark black color of its colonies. It forms slightly fuzzy, circular colonies that both dig into the agar and form short aerial hyphae structures. Photo credit: Erin Carr.

JF2 05-3F “Dopey” microscopy image. This picture was taken using a Nikon Eclipse Ni-E microscope with the 60x objective lens of the microscope. Morphology of this isolate is mostly hyphal, as seen in this image, but the hyphal segments between septae are easily broken off. Growth conditions of this isolate was on MEA for 10 days of growth, then the fungus was scrapped off and diluted in water to obtain a planktonic cell solution for imaging. Thick cell walls typical of black yeast fungi and minimal hyphal branching is observed in this image. Photo credit: Erin Carr.

JF2 05-3F Dopey

JF2 05-3F Dopey is an unknown polyextremotolerant fungal culture whose highest hit in the NCBI database is Uncultured Herpotrichiellaceae clone (FJ554329.1), 95% matching. Phylogenetically, it forms its own clade within Herpotrichiellaceae, outside of the Exophiala and Knufia/Phaeococcomyces clades. Polyextremotolerant fungi are named as such because of their high resistance to many stressors simultaneously, as opposed to extremophiles which live exclusively in extreme conditions (Gostinčar et al., 2012). They are also known as “black yeast fungi”, referring to their highly melanized cell wall, although not all have the yeast morphology (Gostinčar et al., 2012). This fungus was isolated as part of a broader survey of fungal-algal associations in dryland Biological Soil Crusts (BSCs) as funded by NASA’s exobiology program. It was recovered from a BSC community located in Jackman Flats Provincial Park (B.C., Canada). JF2 05-3F Dopey is almost exclusively found in a pseudohyphal form, with the occasional true hyphae. It does not pellet well when centrifuging as pure culture in water. No teleomorphic state has yet been observed for JF2 05-3F but that is typical of black yeast fungi (Untereriner et al., 1995). Extensive phenotyping shows that this isolate can use most standard nitrogen sources to support growth, except proline. It is deficient in the use of several carbon sources, including erythritol, ribose, inositol, and lactose, but is capable of growth on cellobiose. Moreover, JF2 05-3F is resistant to several metals, but not cadmium or nickel. JF2 05-3F’s optimal growth temperature is 22°C, while temperatures above and below caused growth reduction. Growth at 27°C and 4°C was stunted, while growth 37°C and 42°C was not observed.

References:

Gostinčar, C., Muggia, L., & Grube, M. (2012). Polyextremotolerant black fungi: oligotrophism, adaptive potential, and a link to lichen symbioses. Frontiers in Microbiology, 3, 390.

Untereiner, W. A., Straus, N. A., & Malloch, D. (1995). A molecular-morphotaxonomic approach to the systematics of the Herpotrichiellaceae and allied black yeasts. Mycological Research, 99(8), 897-913.