Development of a multi-physics biofilm model incorporating biofilm mechanical and structural characteristics from multi-dimensional imaging datasets acquired by means of optical coherence tomography
Final Report Abstract
On the basis of positioning tests, we proved that the cultivation and monitoring platform ensured an accurate and reliable positioning of the OCT scanner and thus an automated and non-invasive imaging of biofilm replicates. Unintentional detachment of the biofilm by external influences could thus be prevented. A replicate analysis illustrated the need for a minimum number of biofilm replicates and a calculation of several biofilm parameters due to high standard deviations in these parameters as well as in comparison with literature. The influence of the Fe2+ addition on the structural biofilm properties was further demonstrated by means of growth experiments as defined in the project proposal. Thereby, a positive effect of Fe2+ on biofilm development was determined, which was expressed by thicker, faster accumulating and more differentiated “mature” biofilms of high biofilm volume. Biofilm development control can thus be realized by addition of Fe2+ to the cultivation medium. ATR infrared spectroscopy (data not shown) as well as gravimetric measurements confirmed an incorporation of 𝛼- and 𝛽-iron oxide-hydroxide (FeOOH). By comprising additional literature, these iron compounds are known to thrive the development and differentiation of biofilms from suspended bacterial cells and stimulate the production of extracellular polymeric substances. Deformation experiments revealed that biofilms behave differently at elevated shear stress levels and that no defined correlation could be associated between material behavior, iron(II) concentration and volumetric flow rate (iron loading) as well as wall shear stress during growth. Merely, an increased compression of the biofilms could be achieved by adding 2.5 mg/L Fe2+ to the cultivation medium. Here, biofilm age and density gradients within the biofilm (z-direction) may have influenced the investigation. Nevertheless, it was demonstrated, that even after high flow rates (shear stresses) applied, biofilms did not detach entirely in all experiments. At that point, several structural and mechanical biofilm parameters were evaluated to characterize the biofilm stability. Lastly, the project proofed the need for an interdisciplinary approach when it comes to the estimation of correct material properties of biofilms.
Publications
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Determination of mechanical properties of biofilms by modelling the deformation measured using optical coherence tomography. Water Research. 145, 588–598 (2018)
Picioreanu, C., Blauert, F., Horn, H., Wagner, M.
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Introducing a novel, fully-automated cultivation and screening tool for the structural and mechanical investigation of biofilms by means of optical coherence tomography. Biofilms 8, 27th – 29th May 2018
Gierl L., Wagner M. & Horn, H.
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2020, Untersuchungen zum Einfluss von Eisen auf die Struktur und mechanischen Eigenschaften von Bacillus subtilis Biofilmen. ISSN: 2195-2973 Schriftenreihe Bereich Wasserchemie und Wassertechnologie, Band 80. Engler-Bunte-Institut, Karlsruher Institut für Technologie
Gierl, Luisa
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An open-source robotic platform that enables automated monitoring of replicate biofilm cultivations using optical coherence tomography. npj Biofilms Microbiomes 18, 1–9 (2020)
Gierl L., Stoy, K., Faína, A., Horn, H. & Wagner, M.
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Iron as a biofilm control agent: manipulation of biofilm development and differentiation. Biofilms 9, 28th September – 1st October 2020, Karlsruhe, Germany
Gierl L., Horn, H. & Wagner, M.
