Micron Scale Spatial Measurement of the O 2 Gradient Surrounding a Bacterial Biofilm in Real Time

Abstract

O 2 is a fundamental environmental metabolite that affects all life on earth. While toxic to many microbes and obligately required by others, those that have appropriate physiological responses survive and can even benefit from various levels of O 2 , particularly in biofilm communities. Although most studies have focused on measuring O 2 within biofilms, little is known about O 2 gradients surrounding biofilms. Here, we developed electrochemical methodology based on scanning electrochemical microscopy to measure the O 2 gradients surrounding biofilms in real time on the micron scale. Our results reveal that P. aeruginosa biofilms produce a hypoxic zone that can extend hundreds of microns from the biofilm surface and that this gradient remains even after the addition of antibiotic concentrations that eradicated 99% of viable cells. Our results provide a high resolution of the O 2 gradients produced by P. aeruginosa biofilms and reveal sustained O 2 consumption in the presence of antibiotics.