LIFE UNDER HYDRAULIC PRESSURE: BIOFILM ARCHITECTURE AND PYSIOCHEMICAL STATE

Edo Bar-Zeev ¹ Menachem Elimelech ²

¹Department of Environmental Hydrology and Microbiology, Zuckerberg Institute for Water Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Israel
²Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut, USA

Biofilm development, architecture and physiochemical state drastically vary, depending on the nutrients oxygen and shear stresses present. Here I present the role of hydraulic pressure in shaping biofilms. Dynamic and static pressure experiments were carried using reverse-osmosis bench-scale system over 48 hours by pressurizing (up to 55 bar) artificial seawater containing a model bacteria, Pseudoalteromonas atlantica. At the end of each experiment, membranes were imaged by confocal laser scanning microscopy to determine biofilm three-dimensional (3-D) complexity and transmission electron microscopy to estimate cell integrity. Invivo probing by atomic force microscopy was used to quantify biofilm elastic properties. Concurrently, membrane subsections were also tested for biofilm density, biochemical composition and gene expression. Our results highlight that biofouling, developed under dynamic hydraulic pressures (55 bar), appeared as pliable sheets, 30 um thick and composed mainly by a packed layer of live cells. However, under static pressure biofilm developed as mushroom-like structures with different biochemical composition and gene expression. Our results lead us to posit that severe hydraulic stress results in the development of a dense and reinforced biofilm layer that was characterized by low 3-D complexity. The study insights shed new light on the nature of biofilm life in pressurized cross-flow systems.