Elemental Analysis for the Characterization of Antimicrobial Effects.

To address the mounting resistance challenge, novel antibiotics and unprecedented mechanisms of action are urgently needed. In this context, metals have attracted attention in two distinct ways: First, the bacterial metal ion homeostasis is essential for many cellular processes, making it a putatively lucrative antibiotic target. Metal ions are, for example, cofactors for enzymes, and they contribute to signaling and transport processes or to energy metabolism. Possible antibacterial strategies include, for example, depletion of accessible essential metals by sequestration or disruption of metal ion homeostasis by ionophores that transport ions across membranes. Second, organometallic antibiotics that contain metals as integral structural elements can provide unique chemistry with unique modes of action. Since many metal-containing structures used in synthetic chemistry are unprecedented in nature, such antibiotics could circumvent existing mechanisms of resistance. Here, we present a method for quantification of cellular metal/metalloid levels and outline the procedures necessary for antibiotic treatment of Bacillus subtilis, subsequent sample preparation, elemental analysis, and data evaluation. This approach allows to investigate disturbances of the cellular metal ion homeostasis, as well as the localization and quantitation of antibiotics that contain metals rarely found in biological systems, overall aiding in the elucidation of antibiotic mechanisms of action.