For nearly 400 years, microscopes have enabled us to explore and describe the diversity of fungi and to observe the effect of experimental manipulations of the cell population. In the last few decades, three new technologies have transformed our application of microscopes in understanding fungal biology and real-time processes in individual cells. First, computer programmable light microscopes enabled real-time imaging of living cells over periods of hours and days to follow temporal processes; second, molecular genetics enabled us to alter gene expression and track fluorescently tagged proteins and reporters inside cells to understand mechanisms. Third, transferred from the semi-conductor industry, microfabrication methods now allow us to manipulate the physical and chemical environment of individual living cells in real-time in situ on the microscope. This "labon-a-chip" technology is now extending into complex multi-cell and compartmentalized environments in "organ-on-a-chip" applications (Last et al., 2021). The contribution of microfabricated surfaces to our understanding of the biology and interactions of fungal cells is just beginning. This review will discuss the contribution that microfabrication has made to the study of biologic processes of yeast, the exploratory growth of hyphae, and how the viscoelastic properties of soft polymer "chips" have been exploited to quantify fungal force and its impact on fungal morphology.

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Drug resistance and cellular adhesion are two key elements of both dissemination and prevalence of the human fungal pathogen Candida albicans . Smi1 belongs to a family of hub proteins conserved among the fungal kingdom whose functions in cellular signaling affect morphogenesis, cell wall synthesis and stress resistance. The data presented here indicate that C. albicans SMI1 is a functional homolog of Saccharomyces cerevisiae KNR4 and is involved in the regulation of cell wall synthesis. Expression of SMI1 in S. cerevisiae knr4 Δ null mutants rescued their sensitivity to caspofungin and to heat stress. Deletion of SMI1 in C. albicans resulted in sensitivity to the cell-wall-perturbing compounds Calcofluor White and Caspofungin. Analysis of wild-type and mutant cells by Atomic Force Microscopy showed that the Young’s Modulus (stiffness) of the cell wall was reduced by 85% upon deletion of SMI1 , while cell surface adhesion measured by Force Spectroscopy showed that the surface expression of adhesive molecules was also reduced in the mutant. Over-expression of SMI1 , on the contrary, increased cell surface adhesion by 6-fold vs the control strain. Finally, Smi1-GFP localized as cytoplasmic patches and concentrated spots at the sites of new cell wall synthesis including the tips of growing hyphae, consistent with a role in cell wall regulation. Thus, Smi1 function appears to be conserved across fungi, including the yeast S. cerevisiae, the yeast and hyphal forms of C. albicans and the filamentous fungus Neurospora crassa .