With the development of highly sensitive experimental techniques, the mechanical properties of bacterial cells have become an important research topic. However, existing models used to fit experimental data from micro-compression tests often lack accuracy. The aim of this study was to address this limitation by developing a new curve-fitting mathematical model for evaluating the mechanical properties of rod-shaped bacterial cells. The proposed model is based on a thin-shell approach and is specifically designed for the interpretation of single-cell micro-compression experiments. To verify the applicability of the model, single-cell micro-compression tests were performed using a flat-punch nanoindenter tip larger than the bacterial cells. Atomic force microscopy (AFM) was used to obtain detailed morphological information, including precise cell dimensions required for curve fitting. As a model organism, the polyhydroxyalkanoate-producing bacterium Cupriavidus necator H16 was selected due to its ability to accumulate intracellular polyhydroxybutyrate (PHB) granules. For comparison, a mutant strain, C. necator PHB −4 , which lacks PHB production, was also analyzed. The results showed that C. necator H16 cells, with an average PHB content of 72% of dry cell weight, exhibited a Young's modulus approximately 16× higher than that of the PHB −4 mutant, indicating a substantial contribution of intracellular PHB granules to cell stiffness. AFM analysis further revealed that PHB-producing cells were, on average, larger in volume than the non-producing mutant. The combination of AFM and micro-compression testing enabled comprehensive characterization of bacterial cell mechanics and demonstrated a clear correlation between PHB content and mechanical behaviour. • Micro-compression and AFM characterization of bacteria's mechanics and morphology. • New mathematical model for Young's modulus ( E ) evaluation. • Strong correlation was found between PHB content and cell elasticity. • PHB producing bacteria exhibit 16× higher E than the non-producing ones. • Optimisation of mechanical evaluation for rod-shaped cells.
Khyrova et al. (Sun,) studied this question.