THE MECHANICAL PROPERTIES OF AQUATIC BIOFILM MICROORGANISMS AS MEASURED BY BIO-FORCE SPECTROSCOPY

Aquatic biofilms comprise a complex microbial community that often includes algae and fungi, as well as heterotrophic and autotrophic bacteria, reinforced via a matrix of extracellular polymeric substances. To date, most studies have focused on characterizing biofilms under various physicochemical conditions. Yet, there is limited information on the effects of hydraulic pressure on biofilm consortiums. In this study we shed new light on the mechanical properties of microorganisms that comprise aquatic biofilms. Dynamic experiments were conducted in a liquid media using a bio-cell which was inoculated with gram positive and gram negative bacteria as well as cyanobacteria and algae. The mechanical properties were calculated based on force vs. distance measurements between atomic force microscope cantilever (~0.4 N/m) to gram positive and gram negative bacteria, as well as cyanobacteria and algae. Our results show that under forces of up to 15nN, gram negative bacteria P. aeruginosa and E. coli exhibit a two-step deformation profile of 128.2±76.3 nm and 291±62.2 nm, respectively, in addition to partial recovery after the applied pressure. On the other hand, gram positive bacteria A. gonensis and S. aureus displayed a single-step deformation profile of 197±19.7 nm and 111.2±21.3 nm, and no recovery. The viscoelastic and plastic behavior of gram negative and positive bacteria respectively, elucidate the link between mechanical properties of microorganisms to cellular deformation and cell structure. We surmise that further research on the response of microorganisms to pressure will improve our understanding of cellular metabolism, growth and biofilm development in engineered and natural environments.