Effect of static magnetic field (200 mT) on biofilm formation in Pseudomonas aeruginosa

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ORIGINAL PAPER

Effect of static magnetic field (200 mT) on biofilm formation in Pseudomonas aeruginosa Hanini Raouia1 · Beghalem Hamida1 · Aliliche Khadidja1 · Landoulsi Ahmed1 · Chatti Abdelwaheb2 Received: 21 June 2018 / Revised: 20 July 2019 / Accepted: 27 August 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019

Abstract Several studies have investigated the effects of ionizing and non-ionizing radiations on microorganisms. However, the interaction between the magnetic field radiations and bacteria is less studied. The aim of our study was to study the effect of static magnetic field on the biofilm formation in Pseudomonas aeruginosa and its isogenic sod mutants. Our results revealed that the exposure to the static magnetic field (200 mT) increases significantly the swarming in the wild strain. The fliC gene expression did not show significant difference after 6 h exposure of the wild-type strain. The release of some compounds of the biofilm matrix such as rhamnolipids has been considerably enhanced after 6 h of exposure in the wild type. On the other hand, the pyocyanin and biofilm production was increased significantly in all strains compared to controls. Furthermore, our results revealed that the biofilm formation was confirmed by the pslA and ppyR gene expressions. Keywords  Biofilm · Motility · Pseudomonas aeruginosa · sod mutation · Static magnetic field

Introduction Most of the microorganisms promote a lifestyle where the bacterial population is fixed on a support (sessile state) rather than free and isolated in the environment (planktonic). Attachment to a surface is a "survival strategy" that bacteria use to settle and colonize an environment. After attachment, bacteria develop an organized community named "biofilm". Biofilm is defined as a bacterial population adhered to a surface and coated with an exopolysaccharide matrix. The importance of biofilm in the medical field is crucial, since 65% of bacterial infections in humans involve biofilms (Potera 1999). Pseudomonas aeruginosa is an opportunistic pathogen capable of infecting a multitude of hosts such as insects, Communicated by Jorge Membrillo-Hernández. * Hanini Raouia [email protected] 1



Biochemistry and Molecular Biology Unit, Faculty of Science of Bizerte, Carthage University, 7021 Jarzouna, Tunisia



Wastewater Treatment and Valorization Laboratory, Water Research and Technology Center CERTE, Technopole Borj Cedria, 8020 Soliman, Tunisia

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humans and even plants. P. aeruginosa is the major cause of nosocomial infections in immunocompromised patients. This bacterium, when attached to living surfaces, forms biofilm which releases planktonic cells and spreads in other tissues. Several factors may explain the greater resistance of biofilms to antimicrobial agents (Hall-Stoodley and Stoodley 2009; Anderson and O’Tool 2008; Ceri et al. 2010). One of these factors is the polymeric matrix that acts as a barrier to reduce or prevent the diffusion of antimicrobial agents. The electrostatic charges on the surface of the polym