UC San Diego

Microfluidic device has been widely used in biological research, due to not only the dimension, but also its ability of fresh medium supply, medium exchange, gradients generation, and force control. This study applied microfluidic device in research of bacterial behavior, including chemotaxis, thermotaxis, bacterial growth in a gut-like channel, and mechanical stress response. E.coli was used in all our experiments because it is a relatively well-studied organism.

Bacterial chemotaxis is a movement in response to spatially chemical gradients. Similar to chemotaxis, bacterial thermotaxis is the response of bacteria toward spatial temperature gradients. Linear temperature gradients were created by microfluidic device, and E.coli were loaded in the device to test its spatial. The result was surprising, showing that temperature preference of E.coli is a function of temperature gradient rather than a constant.

Organ-on-chip is one of the broad applications of microfluidic device, and we applied it to study bacterial growth in a gut-like channel. The human microbiome in the gut has been shown to play important roles in the health. To better understand the population dynamics of microbes in proximal colon, a gut-like channel was built by a fluidic device called “minigut”. Such device mimicked the contractions and peristaltic movement of human gut. With the minigut device and theoretical analysis, the bacterial spatial density profile could be studied. The results suggest that flow and mixing play a major role in shaping the microbiota of the colon.

Moreover, microfluidic device was applied to study bacterial stress response. A porous device was designed to physically confine E.coli while providing adequate nutrient through diffusion for their growth. The goal was to test the response and molecular regulation of E.coli toward mechanical stress.

Overall, microfluidic device provided appropriate environmental conditions to study bacterial behavior, which could not be done by traditional methods. With such combination between physics and biology, more experimental research could be reached and conducted.