Adaptation of Salmonella enterica Hadar under static magnetic field: effects on outer membrane protein pattern

The present study investigated the adaptation of S. Hadar under the effect of acute static magnetic field exposure (200 mT, 9 h) and the impact on the outer membrane protein pattern. Via two-dimensional electrophoresis (2-DE) and LC-MS/MS spectrometry, we compared the proteome of enriched-outer membrane fraction before and after exposure to a magnetic field. A total of 11 proteins, displaying more than a two-fold change, were differentially expressed in exposed cells, among which 7 were up-regulated and 4 down-regulated. These proteins were involved in the integrity of cell envelope (TolB, Pal), in the response to oxidative stress (OmpW, dihydrolipoamide dehydrogenase, UspF), in the oxidative stress status (bacterioferritin), in virulence (OmpX, Yfgl) or in motility (FlgE and UspF). Complementary experiments associated the down-regulation of FlgE and UspF with an alteration of swarming, a flagella-driven motility, under SMF. Furthermore, the antibiotic disc diffusion method confirmed a decrease of gentamicin susceptibility in exposed cells. This decrease could be partly associated with the up-regulation of TolC, outer membrane component of an efflux pump. OmpA, a multifunctional protein, was up-regulated.SMF (200 mT) seems to maintain the cell envelope integrity and to submit the exposed cells to an oxidative stress. Some alterations suggest an increase of the ability of exposed cells to form biofilms.A large number of attempts to explain biological effects of magnetic fields at the molecular level have been reported for prokaryotes and eukaryotes [1-4]. Usually, biological materials that are used for such investigations are cells [5-7], tissues [8], and living organisms [1,9]. Viability and proliferation [10,11], activity of enzymes [1], transport of ions [12] and gene transcription [13] are the common fields of investigation. All these studies gave contradictory results. Thus, it has been reported that magnetic field (MF) treatment (10 mT, 50 Hz) on different stra