Microfluidic investigation of the impacts of flow fluctuations on the development of Pseudomonas putida biofilms

Abstract

Biofilms play critical roles in wastewater treatment, bioremediation, and medical-device-related infections. Understanding the dynamics of biofilm formation and growth is essential for controlling and exploiting their properties. However, the majority of current studies have focused on the impact of steady flows on biofilm growth, while flow fluctuations are commonly encountered in natural and engineered systems such as water pipes and blood vessels. Here, we investigated the effects of flow fluctuations on Pseudomonas putida biofilm growth through systematic microfluidic experiments and developed a theoretical model to account for such effects. Our experimental results revealed that biofilm growth under fluctuating flow conditions followed three phases: lag phase, exponential phase, and fluctuation phase. In contrast, we observed the four phases of biofilm growth under steady-flow conditions, i.e., lag, exponential, stationary, and decline phases. Furthermore, we demonstrated that low-frequency flow fluctuations promoted biofilm growth, while high-frequency fluctuations inhibited its development. We attributed the contradictory impacts of flow fluctuations on biofilm growth to the adjust time needed for biofilm to grow. Based on the experimental measurements, we developed a theoretical model to predict the growth of biofilm thickness under fluctuating flow conditions. Our study provides insights into the mechanisms underlying biofilm development under fluctuating flows and can inform the design of strategies to control biofilm formation in diverse natural and engineered systems.