The cobalt crust is a vibrant species that can be found throughout an extensive range wherever fallen branches and dead leaves accumulate. In recent publications, I have seen both Terana caerulea and Terana coerulea ambiguously used to describe the species, so I really don’t think one is more accepted than the other. Regardless of what species name you designate for this organism, there is one thing for sure; this species is utterly gorgeous. I have yet to feature a crust fungi in a Fungi Friday, so what better way to do so with such a beautiful species. 

Not only does this saprophytic species grow on woody substrate, but it can also use leaf litter as well as moss as a carbon source. Complex polymers like lignin and cellulose stand no chance against this voracious, enzymatically active white rot fungus. Species like this are keystone species vital to ecosystem health, by unlocking organic molecules that would otherwise remain inaccessible to other fauna and flora. Remember, there is only a limited pool of nitrogen, phosphorus and organic carbon in a given ecosystem, so the flow of energy and nutrients is highly dependent on the saprophytic species that can make these pools readably available. Besides the diversity of fungus within a specific ecosystem, the turnover of these pools is also largely influenced by temperature and moisture content. With this in mind, it’s easy to understand why warmer and wetter ecosystems closer to the equator have such a fast nutrient and energy cycle, especially when the cobalt crust is present.

Unlike us, fungi digest their surrounding exogenously by exuding a mélange of enzymes. The once recalcitrant carbon sources are broken down by these chemical processes, and the available sugars and macronutrients are absorbed into the fungus, which can then be allocated to fungal growth or the production of sexual structures. Some organisms try to take advantage of this exogenous digestion by absorbing the available carbohydrates before the fungus does. These cheaters which usually come in the form of bacteria have driven the evolution of genes involved with antibacterial compounds. The cobalt crust fungus produces an antibacterial metabolite called cortalcerone that reduces the growth of bacteria trying to access a free meal. Although these metabolites are energetically expensive to synthesize, from a fitness perspective, their benefit must outweigh their cost. 

Bacterial-fungal competition has driven the production of antibiotics for millions of years. Several species throughout the animal kingdom have been utilizing these antibacterial metabolites to enhance their own fitness. Human have recently hopped on this train in just the past 100 years with the discovery of penicillin. I’m positive that countless, powerful antibiotics are yet to be discovered from wood rot species, much like the cobalt crust. This is just another reason why we must protect these forest ecosystems. It is the undiscovered metabolites synthesized by forest floor inhabitants that will help humanity fight future virulent infections and illness.