Jeanne Tarrade

Flagella but not type IV pili are involved in the initial adhesion of Pseudomonas aeruginosa PAO1 to hydrophobic or superhydrophobic surfaces

Over the last decades, surface biocontamination has become a major concern in food industries and medical environments where its outcomes could vary from financial losses to public health issues. Understanding adhesion mechanisms of involved microorganisms is essential to develop new strategies of prevention and control. Adhesion of Pseudomonas aeruginosa, a nosocomial pathogenic bacterium, relies on several bacterial features, among which are bacterial appendages such as flagella and type IV pili. Here, we examine the role of P. aeruginosa PAO1 flagella and type IV pili in the adhesion to abiotic surfaces with various hydrophobicities. Adhesion kinetics showed, that after 60min, flagella increased the adhesion of the strain to surfaces with high hydrophobicity while no effect was observed on hydrophilic surfaces. Flagella of adherent bacteria exhibited specific and conserved pattern on the surfaces that suggested a higher affinity of flagella for hydrophobic surfaces. Based on these results and on previous studies in the literature, we proposed a model of flagella-mediated adhesion onto hydrophobic surfaces where these appendages induce the first contact and promote the adhesion of the bacterial body. These findings suggest that anti-bioadhesive surface design should take into consideration the presence of bacterial appendages.

The design of superhydrophobic stainless steel surfaces by controlling nanostructures: A key parameter to reduce the implantation of pathogenic bacteria

Reducing bacterial adhesion on substrates is fundamental for various industries. In this work, new superhydrophobic surfaces are created by electrodeposition of hydrophobic polymers (PEDOT-F4 or PEDOT-H8) on stainless steel with controlled topographical features, especially at a nano-scale. Results show that anti-bioadhesive and anti-biofilm properties require the control of the surface topographical features, and should be associated with a low adhesion of water onto the surface (Cassie-Baxter state) with limited crevice features at the scale of bacterial cells (nano-scale structures).

Super liquid-repellent properties of electrodeposited hydrocarbon and fluorocarbon copolymers

To obtain superoleophobic properties, fluorinated compounds are necessary but they are toxic due to their bioaccumulative potential. This is why, in this article, we investigate superoleophobic materials with minimal fluorinated functions. The strategy used is to associate fluorinated monomer with hydrocarbon monomer, both having the same core (EDOP) in order to have the same oxidation potential for the electrodeposition. Smooth and rough copolymers are produced by the electrodeposition method controlling the deposition charge. In this article, we present the static and dynamic wettability properties of these copolymers with different proportions of fluorinated monomer with water (probe liquid for superhydrophobicity), sunflower oil, hexadecane, dodecane and octane (probe liquids of various surface tension for superoleophobicity) using scanning electron microscopy and optical profilometry. The study of wettability properties of smooth and rough copolymers also permits the determination of their intrinsic hydrophobicity/oleophobicity and to separate the effect of the chemical part from the physical one in the static contact angles. In this article, we show that EDOP-F8 proportion above about 75% is sufficient to obtain wettability properties close to PEDOP-F8 homopolymer, which has exceptional properties with water, sunflower oil and hexadecane. These performances are due to surface nanoporosities promoted by the presence of fluorinated functions. Moreover, the production of smooth copolymers reveals the effect of the chemical part from the physical one in the static contact angles. The chemical part represented between 57% and 74% following the EDOP-F8 fraction for water, about 55% for sunflower oil and about 44% for hexadecane.