Revealing Silver Effects on Bacterial Cell Structure by Atomic Force and Scanning Electron Microscopies

Abstract

The use of silver (Ag+) as an antimicrobial under different forms and at different scales, appears in numerous applications such as in health care, food industry, clothing, fabrics and disinfectants. Yet, there is still important gaps regarding the complete comprehension of the mechanisms of its actions on bacteria. In a previous work, we demonstrated that, silver and copper severly damage membrane proteins involved in photosynthesis and respiration in bacteria exposed to metal excess. Here, we are presenting complementary data using AFM and SEM microscopies, that reveals (i) the drastic effects of Ag+ ions on the morphology and structure of cell membrane and (ii) the formation of Ag+ aggregates that adhere to the bacterial cell surface in Rubrivivax (R.) gelatinosus . Impacts of Ag+ ions on R. gelatinosus are compared to those on the most commonly studied bacteria (Escherichia (E.) coli and Bacillus (B.) subtilis ), while considering the effect of culture grown media on the modification of silver ions. Altogether, these results reveal other levels and subtle aspects of Ag+ toxicity to be taken into account in understanding the general mechanisms of metal toxicity in bacteria.