Crusty-Pinky: A Novel Polyextremotolerant Fungus and its Methylobacterium Symbionts Could be an Essential Symbiosis for the Biological Soil Crust Consortium

Abstract

JF2 08-2F Crusty is a novel melanized polyextremotolerant fungus isolated from a biological soil crust, which we believe harbors Methylobacterium spp. endosymbionts, called Pinky. Crusty is capable of utilizing many sources of carbon and nitrogen and is resistant to multiple metals and UV-C due to its melanized cell wall. We were unable to recover a Pinky-free culture of Crusty via usage of antibiotics. However, when exposed to antibiotics that kill or stop the growth of the Pinky, growth of Crusty is significantly stunted, implying that actively growing Pinky symbionts are needed for Crustys optimal growth. The Crusty-Pinky symbiosis also seems to be able to perform active metabolism in carbonless and nitrogenless medium, which we believe is due to Pinkys ability to perform aerobic anoxygenic photosynthesis. Finally, Pinky was identified as being capable of growth stimulation of the algae Chlorella sorokiniana, indicating that Pinky likely produces cytokinins or auxins which Methylobacterium are known for. Features of this symbiosis provide us insight into the ecological roles of these microbes within the biological soil crust.