title: Exposure of Bacterial Biofilms to Electrical Current Leads to Cell Death Mediated in Part by Reactive Oxygen Species.
abstract: Bacterial biofilms may form on indwelling medical devices such as prosthetic joints, heart valves and catheters, causing challenging-to-treat infections. We have previously described the 'electricidal effect', in which bacterial biofilms are decreased following exposure to direct electrical current. Herein, we sought to determine if the decreased bacterial quantities are due to detachment of biofilms or cell death and to investigate the role that reactive oxygen species (ROS) play in the observed effect. Using confocal and electron microscopy and flow cytometry, we found that direct current (DC) leads to cell death and changes in the architecture of biofilms formed by Gram-positive and Gram-negative bacteria. Reactive oxygen species (ROS) appear to play a role in DC-associated cell death, as there was an increase in ROS-production by Staphylococcus aureus and Staphylococcus epidermidis biofilms following exposure to DC. An increase in the production of ROS response enzymes catalase and superoxide dismutase (SOD) was observed for S. aureus, S. epidermidis and Pseudomonas aeruginosa biofilms following exposure to DC. Additionally, biofilms were protected from cell death when supplemented with antioxidants and oxidant scavengers, including catalase, mannitol and Tempol. Knocking out SOD (sodAB) in P. aeruginosa led to an enhanced DC effect. Microarray analysis of P. aeruginosa PAO1 showed transcriptional changes in genes related to the stress response and cell death. In conclusion, the electricidal effect results in death of bacteria in biofilms, mediated, at least in part, by production of ROS.
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, United States of America.
authors.forename: Cassandra L
authors.initials: CL
authors.lastname: Brinkman
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, United States of America.
authors.forename: Suzannah M
authors.initials: SM
authors.lastname: Schmidt-Malan
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, United States of America.
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Karau
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, United States of America.
authors.forename: Kerryl
authors.initials: K
authors.lastname: Greenwood-Quaintance
authors.affiliation: Department of Molecular Genetics, Biochemistry & Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Hassett
authors.affiliation: Division of Biomedical Statistics and Informatics, Department of Health Sciences Research Mayo Clinic, Rochester, MN, United States of America.
authors.forename: Jayawant N
authors.initials: JN
authors.lastname: Mandrekar
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, United States of America.|Division of Infectious Diseases, Department of Medicine, Mayo Clinic, Rochester, MN, United States of America.
authors.forename: Robin
authors.identifier: http://orcid.org/0000-0001-6344-4141
authors.initials: R
authors.lastname: Patel
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development*; D004560:Electricity; D055785:Gene Knockdown Techniques; D006090:Gram-Negative Bacteria / Q000502:physiology*; D006094:Gram-Positive Bacteria / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D017382:Reactive Oxygen Species; D013482:Superoxide Dismutase