Colony differentiation of saprobic and pathogenic fungi in relation to carbon utilization

Carbon utilization is crucial for the cellular functions of all fungi and is highly dependent on the prevalent carbon sources in the environment. In natural environments, plant biomass is a major carbon source for most saprobic and pathogenic filamentous fungi and its utilization requires a complex process involving extracellular enzymes, sugar transporters and metabolic pathways, governed by a network of transcriptional regulators. Filamentous fungi form extensive colonies that encounter highly diverse environmental conditions and available carbon levels, which raises the question if, and to which extent, parts of the colony exposed to sufficient carbon source levels can support other parts that are under carbon limitation or starvation. While it is difficult to mimic the heterogenic natural conditions in a laboratory experiment, several studies into carbon translocation, and colony and hyphal differentiation have provided insights into this complex biological process. These studies are reviewed here and their insights are re-assessed and combined into a current state of the art of this field.