Cyclic-di-GMP and oprF Are Involved in the Response of Pseudomonas aeruginosa to Substrate Material Stiffness during Attachment on Polydimethylsiloxane (PDMS)

Fangchao Song,Dacheng Ren,Hao Wang,Karin Sauer

doi:10.3389/fmicb.2018.00110

Fangchao Song, Dacheng Ren + Show 2 more

Open Access

https://doi.org/10.3389/fmicb.2018.00110

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Abstract

Recently, we reported that the stiffness of poly(dimethylsiloxane) (PDMS) affects the attachment of Pseudomonas aeruginosa, and the morphology and antibiotic susceptibility of attached cells. To further understand how P. aeruginosa responses to material stiffness during attachment, the wild-type P. aeruginosa PAO1 and several isogenic mutants were characterized for their attachment on soft and stiff PDMS. Compared to the wild-type strain, mutation of the oprF gene abolished the differences in attachment, growth, and size of attached cells between soft and stiff PDMS surfaces. These defects were rescued by genetic complementation of oprF. We also found that the wild-type P. aeruginosa PAO1 cells attached on soft (40:1) PDMS have higher level of intracellular cyclic dimeric guanosine monophosphate (c-di-GMP), a key regulator of biofilm formation, compared to those on stiff (5:1) PDMS surfaces. Consistently, the mutants of fleQ and wspF, which have similar high-level c-di-GMP as the oprF mutant, exhibited defects in response to PDMS stiffness during attachment. Collectively, the results from this study suggest that P. aeruginosa can sense the stiffness of substrate material during attachment and respond to such mechanical cues by adjusting c-di-GMP level and thus the following biofilm formation. Further understanding of the related genes and pathways will provide new insights into bacterial mechanosensing and help develop better antifouling materials.

Highlights

Biofilms are communities of bacteria attached on surfaces and embedded in a self-produced matrix comprised of polysaccharides, DNA, and proteins (Arenas and Tommassen, 2016; Flemming et al, 2016)
We recently reported that the stiffness of PDMS has profound effects on the adhesion of E. coli and P. aeruginosa, as well as the growth, morphology, and antibiotic susceptibility of attached cells (Song and Ren, 2014)
We demonstrated that mutation of oprF abolished the response by P. aeruginosa to material stiffness during attachment and early biofilm formation on PDMS surfaces, which was rescued by complementing the oprF gene

Summary

Introduction

Biofilms are communities of bacteria attached on surfaces and embedded in a self-produced matrix comprised of polysaccharides, DNA, and proteins (Arenas and Tommassen, 2016; Flemming et al, 2016). A number of material properties influence biofilm formation (Song et al, 2015), such as surface chemistry (Cheng et al, 2007; Hou et al, 2009; Renner and Weibel, 2011), stiffness (Lichter et al, 2008; Saha et al, 2013; Guégan et al, 2014; Kolewe et al, 2015), hydrophobicity (Packham, 2003), topography (Hou et al, 2011; Singh et al, 2011; Crawford et al, 2012; Perni and Prokopovich, 2013), and charges (An and Friedman, 1998; Renner and Weibel, 2011). We reported that decrease in the stiffness of crosslinked poly(dimethylsiloxane) (PDMS) promotes the adhesion and growth of Escherichia coli and P. aeruginosa; and the attached bacterial cells on soft surfaces are longer and less tolerant to antibiotics (Song and Ren, 2014). These findings motivated us to further investigate what genes and pathways of P. aeruginosa are involved in its response to PDMS stiffness during attachment

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