Algal cell nanomechanical properties and adhesion dynamics at the model interface

We examine the nanomechanical properties and adhesion dynamics of the marine, unicellular, green flagellate Dunaliella tertiolecta in laboratory culture. Mechanical properties of motile cells are hard to access while keeping cells viable, and studies to date are limited. Immobilization of negatively charged cells to a positively charged substrate enables high-resolution imaging and nanomechanical measurements. Cells in exponential phase possess a large cell volume as imaged by AFM, in agreement with the large amount of amperometrically measured displaced charge at the interface. Cells are stiffer and more hydrophobic in exponential than in the stationary phase. Differences in the critical interfacial tensions of adhesion of cells in exponential and stationary phase show the analogy with adhesion of hydrophobic droplets of organic liquids. Differences in the kinetics of adhesion and spreading of cells at the interface are attributed to their volume and nanomechanical properties that vary during cell aging. Cell mechanical properties could be considered as a marker for environmental stress in order to better understand viability and adaptation strategies of algal populations in aquatic systems.