Microfluidic Experiments Demonstrate the Effects of Flow Fluctuations on Biofilm Growth

Biofilms play critical roles in various environmental processes within porous media, influencing nutrient cycling, bioremediation, and hydrogeological transport. Understanding the dynamics of biofilm formation and growth is essential for predicting and controlling biofilm properties in soil, yet such process has not been fully understood. The majority of current studies have focused on the impact of steady flows on biofilm growth, while flow fluctuations are commonly encountered in porous media, especially soil. In this study, we investigated the effects of flow fluctuations on the growth of biofilms of a soil bacterium Pseudomonas putida through a combination of microfluidic experiments and theoretical models. Our experimental results revealed that biofilm growth under fluctuating flow conditions followed three distinct phases: lag, exponential, and fluctuation phases, in contrast to the four phases under steady flow conditions (lag, exponential, stationary, and decline phases). We demonstrated that low-frequency fluctuations promoted biofilm growth, while high-frequency fluctuations inhibited its development. We attributed the contradictory impacts of flow fluctuations on biofilm growth to the adjustment time (<!--[if gte msEquation 12]> style='font-family:"Cambria Math","serif";mso-ascii-font-family:"Cambria Math";
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