The yeast Saccharomyces cerevisiae and the microalga Chlorella vulgaris were mechanically characterized using single-cell compression experiments. Micro-mechanical cell characteristics could be calculated directly from the force displacement data. The mechanical properties of the cell wall were determined with different analytical models because the intrinsic parameters of the cell wall cannot be measured directly. As expected, the Young's moduli obtained from the cellular model and the cell wall model differ by two orders of magnitude. Although yeast and algal cells need similar forces to get disrupted, the bursting deformation and bursting energy of the algal cells are about two times smaller. Based on the dry biomass, the energy for cell breakage of C. vulgaris is about six times higher than that of S. cerevisiae. Finally, the tensile strength of the cell wall was calculated.