Abstract
Investigation of biofilms and visualization using non-destructive imaging techniques like X-ray μCT has recently gained interest. Biofilms are congregations of microorganisms that attach to surfaces and comprise of microbial cells embedded in extracellular polymeric substances (EPS). They are ubiquitous entities that are commonly found in any non-sterile setting and have direct implications on human health. Methods to visualize them in-situ are highly needed to understand their behaviour (attachment and detachment) inside a substrate. Contrast-enhanced X-ray μCT is a 3D imaging technique that is capable of visualising objects that have very low attenuation contrast. The use of contrast agents in X-ray μCT has been an evolving process, however, the possible toxic effect of these chemical compounds against biofilms has not been studied in detail. In this study, we focus on the toxic effect of contrast agents and study the diffusion and drainage of contrast agents in biofilms. We propose using water-soluble potassium bromide (KBr) as a suitable contrast agent for enhancement of the attenuation coefficient of a monoculture of Pseudomonas fluorescens biofilms inside a porous substrate. At the given concentration, KBr proved to be less bactericidal compared to other commonly used contrast agents and at 5% w/v concentration we were able to clearly distinguish between the biofilm and the porous substrate.
Highlights
Bacteria do not live in isolation, but in bacterial communities [1,2] in which they can have several kinds of interactions, including cooperation and competition [3]
As an ideal case, for simulation, it was considered that the concentration of contrast agent inside the biofilms and the concentration of the initially applied KBr solution are the same
This work focused on in-situ visualisation of biofilms inside a porous substrate using X-ray μCT
Summary
Bacteria do not live in isolation, but in bacterial communities [1,2] in which they can have several kinds of interactions, including cooperation and competition [3]. One notorious form of bacterial communities are biofilms [4], which can be defined as bacterial aggregates located on an interface and surrounded by a protective layer of extracellular polymeric substances (EPS) [5] These biofilms offer several benefits to the bacteria, including increased attachment to surfaces and protection against external stresses, which include biocides and antibiotics [6]. Bacterial biofilms can be beneficial and important in biotechnological applications (for production of bulk chemicals and enzymes) [9,10] and can be applied in agriculture (bioremediation and growth promotion) [11], wastewater treatment [12] and as an anticorrosive strategy [13] Given their increased tolerance to disinfectants (glutaraldehyde, sodium hypochlorite) [14], antimicrobial agents [15], metal ions and halogenated ions [16,17,18], biofilms [16,19]
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