Abstract
Biofilm formation is a harmful phenomenon in many areas, such as in industry and clinically, but offers advantages in the field of biocatalysis for the generation of robust biocatalytic platforms. In this work, we optimised growth conditions for the production of Escherichia coli biofilms by three strains (PHL644, a K-12 derivative with enhanced expression of the adhesin curli; the commercially-used strain BL21; and the probiotic Nissle 1917) on a variety of surfaces (plastics, stainless steel and PTFE). E. coli PHL644 and PTFE were chosen as optimal strain and substratum, respectively, and conditions (including medium, temperature, and glucose concentration) for biofilm growth were determined. Finally, the impact of these growth conditions on expression of the curli genes was determined using flow cytometry for planktonic and sedimented cells. We reveal new insights into the formation of biofilms and expression of curli in E. coli K-12 in response to environmental conditions.
Highlights
Biofilms represent a ubiquitous mode of growth for many microbes (Donlan 2002)
To complement the spin-coating methods, we developed methods of biofilm growth that relied upon natural biofilm formation by non-pathogenic E. coli strains
Three non-pathogenic strains of E. coli were used: PHL644, a K-12 derivative with an ompR234 allele conferring overexpression of the adhesin curli via upregulation of the curli master regulator CsgD (Vidal et al 1998); BL21 star (DE3), referred to here as BL21, a B strain commonly used for recombinant protein production (Invitrogen); and the probiotic Nissle 1917, which has been previously reported to form biofilms well (Hancock et al 2010)
Summary
Bacteria attach to solid surfaces in first a reversible, an irreversible, manner; bacteria multiply, forming microcolonies, and synthesise extracellular polymeric substances (EPS), generating a matrix and providing structure to the biofilm. These molecular determinants of each phase of biofilm development are tightly regulated in response to environmental stimuli and are highly. Bacteria in biofilms are frequently more resistant to chemical and physical stresses (Koo et al 2017) and antibiotics (reviewed by (Olsen 2015)) than planktonic bacteria and, represent a clinical problem in indwelling medical devices (Arciola et al 2018). Biofilms are resistant to cleaning in industrial settings such as industrial food processing (Coughlan et al 2016) and on the underside of ships (Banerjee et al 2011)
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