We Stress Bacteria out: Dynamic Responses of Bacteria to Fluid, Nanoparticle, and Antibiotic Stress.

Our engineered environments concentrate and put bacteria under a lot of stress. However, we know for humans that there is good and bad stress. We explore how three different stressors and attempt to classify those stress responses to help both disease treatment and bioprocessing. We show that increased shear stress increases the metabolism of electroactive active bacteria independently of mass stress in a pure culture biofilm. We use a rotating disc electrode to decouple mass transport from shear stress. We find increased shear stress reduces biofilm development time while increasing its metabolic rate. Furthermore, biofilm health is negatively affected by higher metabolic rates over long-term growth due to the biofilm’s memory of the fluid flow conditions during the initial biofilm development phases.

We also show that bacteria growth curves can be used to predict resistance or tolerance development when bacteria are exposed to nanoparticles and antibiotics. We use machine learning approaches to rapidly classify survival behavior across nanoparticle types and concentrations. We compare 1000 experimental interactions between Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis,Pseudomonas aeruginosa,Helicobacter pyloriand concentrations of liposomal drug delivery systems, amphiphilic peptide, and silver and selenium nanoparticles. Clustering reveals bacteria-nanoparticle clusters separate resistance and tolerance development from stable growth. Furthermore, bacteria-generated nanoparticles do not induce growth dynamics associated with resistance.