Abstract
Flagellar motility is important for the pathogenesis of many intestinal pathogens, allowing bacteria to move to their preferred ecological niche. Clostridioides difficile is currently the major cause for bacterial health care-associated intestinal infections in the western world. Most clinical strains produce peritrichous flagella and are motile in soft-agar. However, little knowledge exists on the C. difficile swimming behaviour and its regulation at the level of individual cells. We report here on the swimming strategy of C. difficile at the single cell level and its dependency on environmental parameters. A comprehensive analysis of motility parameters from several thousand bacteria was achieved with the aid of a recently developed bacterial tracking programme. C. difficile motility was found to be strongly dependent on the matrix elasticity of the medium. Long run phases of all four motile C. difficile clades were only observed in the presence of high molecular weight molecules such as polyvinylpyrrolidone (PVP) and mucin, which suggests an adaptation of the motility apparatus to the mucin-rich intestinal environment. Increasing mucin or PVP concentrations lead to longer and straighter runs with increased travelled distance per run and fewer turnarounds that result in a higher net displacement of the bacteria. The observed C. difficile swimming pattern under these conditions is characterised by bidirectional, alternating back and forth run phases, interrupted by a short stop without an apparent reorientation or tumbling phase. This motility type was not described before for peritrichous bacteria and is more similar to some previously described polar monotrichous bacteria.
Highlights
Clostridioides difficile is a spore forming, obligate anaerobic pathogen that causes CDI (C. difficile infection), which predominantly manifests as hospital-associated diarrhoea and pseudomembranous colitis (Leffler and Lamont, 2015; Lessa et al, 2015)
A large-scale quantitative analysis of the swimming behaviour leads to the conclusion that the single cell motility displayed by C. difficile forms a novel pattern for peritrichous bacteria, which we describe here in detail
When C. difficile 630 erm swimming behaviour was analysed in 100% BHIS medium or in a 10% BHIS 90% PBS mixture, the bacteria could be classified into two groups
Summary
Clostridioides (formerly Clostridium) difficile is a spore forming, obligate anaerobic pathogen that causes CDI (C. difficile infection), which predominantly manifests as hospital-associated diarrhoea and pseudomembranous colitis (Leffler and Lamont, 2015; Lessa et al, 2015). Flagellar motility and chemotaxis are important for successful colonisation and virulence of many gastrointestinal pathogens, for example Campylobacter jejuni, Salmonella enterica Serovar Typhimurium, Helicobacter pylori, and Vibrio chlolerae (Boin et al, 2004; Stecher et al, 2004; Lertsethtakarn et al, 2011; Korolik, 2019). Most C. difficile strains produce peritrichous flagella, which can mediate swimming motility in soft-agar based assays (Twine et al, 2009; Baban et al, 2013; Courson et al, 2019). Chemotaxis allows bacteria to swim up or down a chemical gradient and to find optimal growth conditions (Matilla and Krell, 2018). The phosphorylated CheY interacts with the flagellar motor and leads to a modulation of motility characteristics
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