Nuclear magnetic resonance microscopy of Staphylococcus epidermidis biofilms

Abstract

Nuclear Magnetic Resonance (NMR) microscopy is well-suited for investigating living systems since it is innocuous and non-invasive. In addition to imaging internal structures of systems, NMR microscopy techniques can be used to obtain information about transport phenomena, such as fluid velocities and diffusion. The goal of this research was to determine the applicability of NMR imaging techniques to studying transport properties in biofilms. Staphylococcus epidermidis biofilms were investigated because of their importance in medical implant infections. NMR experiments were used to image biofilm structure and the fluid flow patterns in one millimeter square glass capillaries. Results showing the heterogeneous structure of biofilms are congruent with confocal laser microscopy images. The advantage of using the NMR techniques to image biofilm structures is that there are no light or laser penetration barriers and the innermost regions of the structures can be easily revealed. In addition to imaging the biofilms, velocity distributions have been mapped for the one millimeter capillary system. Laminar flows in clean, square capillaries display axial velocities that are both uniform and symmetrical while non-axial components of velocity are not present. In contrast, a biofilm fouled capillary displays irregular flow patterns in the axial direction along with distinct non-axial secondary flow perturbations. These results demonstrate that biofilms impact bulk flow in ways that cannot be ignored when modeling their impact on transport in bioreactors and medial devices. This work establishes NMR microscopy as an important biofilm research tool which can spatially resolve structural characteristics and transport processes in biofilm fouled systems.