To improve the efficiency of isolating and culturing lichen mycobionts, we performed a growth assay on an Australian strain of the soil-crust lichenized fungus Endocarpon pusillum Hedw. This assay determined the preferred nitrogen and carbon sources of the fungus by limiting the available nitrogen or carbon sources to single compounds found in soils, plants and lichen thalli. We found that the non-proteinaceous amino acid, GABA, produced the most growth of all nutrients when provided as the sole nitrogen source but was a poor carbon source. Fructose, glucose, cellobiose and sorbitol produced the most growth of all the carbon sources tested. Ammonium, nitrate and polyamines were poor nutrient sources. These findings correspond with reports of primary metabolite pools in other lichen species and may guide future studies involving growth of recalcitrant lichen mycobionts. Keywords: aminobutyric, GABA, growth, medium, nutrition, polyalcohol, polyol, rate.