Redox-active conducting polymers modulate Salmonella biofilm formation by controlling availability of electron acceptors

• Published in: NPJ biofilms and microbiomes 2017, Vol.3 (1), p.19-10, Article 19
• Main Authors: Gomez-Carretero, Salvador, Libberton, Ben, Svennersten, Karl, Persson, Kristin, Jager, Edwin, Berggren, Magnus, Rhen, Mikael, Richter-Dahlfors, Agneta
• Format: Article
• Language: English
• Subjects: 631/326/252/22; 631/326/2522; 631/326/2565; 631/326/46; 631/326/88; Biofilms; Biomedical and Life Sciences; Electron transfer; Food industry; Food processing; Fouling; Life Sciences; Medical equipment; Medical Microbiology; Medicin och hälsovetenskap; Microbial Ecology; Microbial Genetics and Genomics; Microbiology; Polymers; Salmonella
• ISSN: 2055-5008; 2055-5008
• DOI: 10.1038/s41522-017-0027-0

Biofouling is a major problem caused by bacteria colonizing abiotic surfaces, such as medical devices. Biofilms are formed as the bacterial metabolism adapts to an attached growth state. We studied whether bacterial metabolism, hence biofilm formation, can be modulated in electrochemically active surfaces using the conducting conjugated polymer poly(3,4-ethylenedioxythiophene) (PEDOT). We fabricated composites of PEDOT doped with either heparin, dodecyl benzene sulfonate or chloride, and identified the fabrication parameters so that the electrochemical redox state is the main distinct factor influencing biofilm growth. PEDOT surfaces fitted into a custom-designed culturing device allowed for redox switching in Salmonella cultures, leading to oxidized or reduced electrodes. Similarly large biofilm growth was found on the oxidized anodes and on conventional polyester. In contrast, biofilm was significantly decreased (52–58%) on the reduced cathodes. Quantification of electrochromism in unswitched conducting polymer surfaces revealed a bacteria-driven electrochemical reduction of PEDOT. As a result, unswitched PEDOT acquired an analogous electrochemical state to the externally reduced cathode, explaining the similarly decreased biofilm growth on reduced cathodes and unswitched surfaces. Collectively, our findings reveal two opposing effects affecting biofilm formation. While the oxidized PEDOT anode constitutes a renewable electron sink that promotes biofilm growth, reduction of PEDOT by a power source or by bacteria largely suppresses biofilm formation. Modulating bacterial metabolism using the redox state of electroactive surfaces constitutes an unexplored method with applications spanning from antifouling coatings and microbial fuel cells to the study of the role of bacterial respiration during infection. Biofilm control: An electrifying effect Biofilm formation on surfaces can be inhibited or promoted by controlling the availability of electrons and electron-acceptors. This offers a novel way to protect medical devices and machinery from biofilm fouling. It could also assist studies of bacterial metabolism during the formation of biofilms. Agneta Richter-Dahlfors and colleagues at the Swedish Medical Nanoscience Center at Karolinska Institutet investigated the effect with cultured Salmonella bacteria. They used electrodes composed of an electrically conducting polymer to maintain the surfaces exposed to bacteria in an electron-rich or electron-deficient s