Measuring local flow velocities and biofilm structure in biofilm systems with Magnetic Resonance Imaging (MRI)

Abstract

Abstract:The characterization of substrate transport in the bulk phase and in the biofilm matrix is one of the problems which has to be solved for the verification of biofilm models. Additionally, the surface structure of biofilms has to be described with appropriate parameters. Magnetic resonance imaging (MRI) is one of the promising methods for the investigation of transport phenomena and structure in biofilm systems. The MRI technique allows the noninvasive determination of flow velocities and biofilm structures with a high resolution on the sub-millimeter scale. The presented investigations were carried out for defined heterotrophic biofilms which were cultivated in a tube reactor at a Reynolds number of 2000 and 8000 and a substrate load of 6 and 4 g /m 2 d glucose. Magnetic resonance imaging provides both structure data of the biofilm surface and flow velocities in the bulk phase and at the bulk/biofilm interface. It is shown that the surface roughness of the biofilms can be determined in one experiment for the complete cross section of the test tubes both under flow and stagnant conditions. Furthermore, the local shear stress was calculated from the measured velocity profiles. In the investigated biofilm systems the local shear stress at the biofilm surface was up to 3 times higher compared to the mean wall shear stress calculated on the base of the mean flow velocity.

Functional and structural imaging of phototrophic microbial communities and symbioses

“…NMR imaging studies in environmental microbiology have been conducted on microbial mats (Wieland et al 2001), biofilms (e.g. Manz et al 2003, Majors et al 2005) and sponges (Bringmann et al 1999). Application of NMR microscopy for the analysis of single cells and aggregates of microorganisms is a fascinating new method that has just been introduced to microbiology (McLean et al 2008).…”

Three-dimensional Magnetic Resonance Imaging of fossils across taxa

“…For all these applications, suitable MR techniques are now in place (e.g. Ciobanu et al, 2003;Manz et al, 2003;Müller et al, 2006;Lee et al, 2006Lee et al, , 2007Honda and Hata, 2007). This versatility of MR techniques, along with their non-invasiveness, renders them a very promising tool for such comparative investigations (e.g.…”

Numerical Simulation of Fluid Flow and Hydrodynamic Analysis in Commonly Used Biomedical Devices in Biofilm Studies

“…blood, water or oil) is a source of nutrients, it also governs the transport of signaling molecules or of the bacteria and can provide the mechanical stimulus for regulating gene expression. Hence, the hydrodynamics of the fluid over biofilms is one of the more important factors affecting biofilm formation, structure and activity (Christensen, 1989;Stoodley et al, 1999;Purevdorj et al, 2002;Manz et al, 2003;Chen, 2005;Gjersing et al, 2005;Salek et al, 2009). The flow field affects each process of biofilm formation by changing the substrate concentration around the colonies, which influences the transport of bacteria and nutrients, and regulates the physiological properties of these complex structures by changing the mechanical shear stresses at the fluid-biofilm interface.…”

“…A broad range of techniques and models have been developed for in-vitro studies of the biofilm behavior under different environmental conditions. Among these, different types of tube flow cells are widely used to manipulate the hydrodynamics of flow around the biofilms (Manz et al, 2003;Gjersing et al, 2005). Tube flow cells and parallel plate flow chambers are commonly used in biofilm and microbiology studies to manipulate the hydrodynamics of flow surrounding the biofilms.…”

“…Hosoi et al (1986) investigated the effects of fluid velocity and shear on the biofilm formation in round pipes and found that an optimum shear to maximize the biofilm accumulation existed. Manz et al (2003) imaged the velocity distribution over the biofilms in round tubes and showed that the local shear stress calculated from the measured velocity profiles at the biofilm interface was higher than the average wall shear stress calculated on the base of the mean flow velocity. This coupling between the stress field and biofilm growth illustrates the need for a detailed knowledge of the near-wall flow even in for the apparently simple round tube flow cell.…”