Label-free fluorescence microscopy in fungi

• Nonlinear microscopy allows studying fungi noninvasively.
• Nonlinear microscopy as a tool to study growth and development of fungi.
• Nonlinear microscopy as a tool to monitor industrial fermentations.
• Nonlinear microscopy as a tool for taxonomy, diagnostics and quality control.

Label-free fluorescence microscopy detects fluorescence originating from endogenous fluorophores, such as NAD(P)H, melanin and flavins. The emitted fluorescence (spectrum, lifetime and polarization) is characteristic for the molecule and its environment. In most cases, a specimen contains multiple autofluorescent molecules contributing to the overall fluorescence. Methods have been developed to break down the fluorescence into the contribution of its individual components. As a result, label-free microscopy can map biochemical properties of fluorophores spatially and over time at the level of the organism, tissue and cells. This is of interest for fungal cell biology and development. Moreover, it can be used in biotechnological applications to monitor the metabolic state within a bioreactor or to monitor the formation of secondary metabolites. Combining morphological and biochemical properties can also lead to new developments in fungal taxonomy, biomedical diagnostics, as well as the screening of fungal products such as mushrooms.