Chemotactic study of Escherichia coli towards alanine using a microfluidics platform.

Chemotaxis, the capacity of cells and microorganisms to detect and respond to chemical gradients, is integral to various biological processes, including biofilm formation, environmental decontamination, pathogen identification, and targeted drug delivery. This study involved the fabrication of a Y-shaped microfluidic device to examine the chemotactic migration of Escherichia coli K12 DH5α toward gradient concentrations of alanine, an amino acid that serves as a potent chemoattractant for E. coli. The microfluidic device was designed and fabricated using standard photolithography and soft lithography techniques, and computational fluid dynamics (CFD) simulations were conducted using ANSYS Fluent to analyze the laminar flow behavior within the device. CFD simulations of phosphate-buffered saline (PBS) co-flow with 2 μm bacterial-sized particles predicted creeping, low-Reynolds-number laminar flow characterized by parallel, non-mixing streams, stable velocity profiles, and a smooth pressure drop of approximately 1.45 Pa toward the outlet. These results confirm the formation of a sharp interfacial boundary suitable for gradient-based chemotaxis assays. The chemotactic response of green fluorescent protein (GFP)-tagged E. coli was quantified by measuring fluorescence intensity in the central channel of the device. The results demonstrated that bacterial migration was dependent on alanine concentration, with maximum cell migration observed at 10 mM alanine. The bacteria exhibited motility perpendicular to the direction of streamlined laminar flow, migrating toward regions of higher alanine concentration. This study introduces a gradient-based Y-shaped microfluidic platform, validated through computational fluid dynamics (CFD), which integrates fluorescence-based quantification of GFP-tagged E. coli K12 DH5α chemotaxis. This platform facilitates real-time, reproducible, and concentration-dependent analysis of bacterial migration towards alanine under controlled laminar flow conditions. In contrast to traditional chemotaxis assays, it allows for precise chemical gradient generation, direct visualization of bacterial movement, and quantitative assessment of chemotactic responses within a single microfluidic system. The study provides both qualitative and quantitative insights into bacterial chemotaxis and highlights the potential of microfluidic platforms for real-time analysis of cellular behavior. The findings contribute to the advancement of rapid biosensing technologies and enhance the understanding of bacterial responses to chemical stimuli, with promising applications in biotechnology, microbiology, and environmental science.