Bacterial chemotaxis transverse to axial flow in a microfluidic channel

Abstract

Swimming bacteria sense and respond to chemical signals in their environment. Chemotaxis is the directed migration of a bacterial population toward increasing concentrations of a chemical that they perceive to be beneficial to their survival. Bacteria that are indigenous to groundwater environments exhibit chemotaxis toward chemical contaminants such as hydrocarbons, which they are also able to degrade. This phenomenon may facilitate bioremediation processes by bringing bacteria into closer proximity to these contaminants. A microfluidic device was assembled to study chemotaxis transverse to advective flow. Using a T-shaped channel design (T-sensor), two fluid streams were brought into contact by impinging flow. They then flowed adjacent to each other along a transparent channel. An advantage to this design is that it allows real-time visualization of bacterial distributions within the channel. Under laminar flow conditions a chemotactic driving force was created perpendicular to the direction of flow by diffusion of the chemical attractant from one input stream to the other. A comparison of the chemotactic band behavior in the absence and presence of flow showed that fluid velocity did not significantly impede chemotactic migration in the transverse direction.

Flow-Based Microfluidic Device for Quantifying Bacterial Chemotaxis in Stable, Competing Gradients

“…In our Flow device, bacteria entering the chemotaxis chamber immediately encounter established gradients of chemoeffectors, and the cells experience a stable gradient throughout the length of the channel. This situation contrasts with those of the systems described previously by Mao et al (23) and Lanning et al (18), in which gradients are established in the observation chamber such that the bacteria flowing through the chamber are exposed to a changing gradient. This difference in design leads to a longer time available for cells to respond to the gradient in our device, making it more appropriate for investigating signals that elicit weaker responses.…”

“…Variations of this technique, such as three-channel microfluidic devices (7,8) in which a linear gradient is generated in the absence of flow or a T-channel device that monitors chemotaxis perpendicular to the direction of fluid flow (18), were developed subsequently. The T-channel system has many of the limitations of the device developed by Mao et al (23), and nonflow systems, like the capillary assay (1), suffer from a lack of temporal stability of the gradients.…”

About the choice of methods for solving Poisson's equation in the general case of the distribution of the volume charge density and about the formulation of boundary conditions in electrokinetic problems (review)

“…Модификация описанного выше T-устройства была представлена в работе [48], в которой ис-пользовались только два загрузочных канала. Че-рез один из каналов происходила подача раствора с хемоаттрактантом, а через другой буферного раствора.…”

“…Из канала, расположенного перпен-дикулярно относительно оси симметрии широкого канала, подавалась суспензия бактерий в область, где градиент хемоаттрактанта достигал наиболь-ших значений. По приоритетному смещению бак-терий к концу канала, авторы судили о величине хемотаксиса.Модификация описанного выше T-устройства была представлена в работе [48], в которой ис-пользовались только два загрузочных канала. Че-рез один из каналов происходила подача раствора с хемоаттрактантом, а через другой буферного раствора.…”

Studying physical and biochemical interactions in bacterial communities using microfabricated devices

“…In the last decade several microfluidic devices were developed for bacterial chemotaxis studies. The majority of these gradient generators rely on fluid flow [107,117,118]. Although, gradients can be established in these devices, in most of the cases bacteria are only exposed to the gradient for a short time [119][120][121], or separately in another microchannel [122][123][124][125][126][127] to allow the chemical gradient establishment.…”