title: Antimicrobial properties of magnesium chloride at low pH in the presence of anionic bases.
abstract: Magnesium is an element essential for life and is found ubiquitously in all organisms. The different cations play important roles as enzymatic co-factors, as signaling molecules, and in stabilizing cellular components. It is not surprising that magnesium salts in microbiological experiments are typically associated with positive effects. In this study with Listeria monocytogenes as a model organism, we focus however on the usefulness of magnesium (in form of MgCl2) as a stress enhancer. Whereas MgCl2 does not affect bacterial viability at near-neutral pHs, it was found to strongly compromise culturability and redox activity when cell suspensions were exposed to the salt at acidic pH. The principle was confirmed with a number of gram-negative and gram-positive species. The magnesium salt dramatically increased the acidity to a level that was antimicrobial in the presence of anionic bases such as phosphate, lactate, or acetate, but not TRIS. The antimicrobial activity of MgCl2 was much stronger than that of NaCl, KCl, or CaCl2. No effect was observed with MgSO4 or when cells were exposed to MgCl2 in phosphate buffer with a pH ≥ 5. Acid stress was reinforced by an additional, salt-specific effect of MgCl2 on microbial viability that needs further examination. Apart from its implications for surface disinfection, this observation might support the commonly stated therapeutic properties of MgCl2 for the treatment of skin diseases (with healthy skin being an acidic environment), and could contribute to understanding why salt from the Dead Sea, where Mg(2+) and Cl(-) are the most abundant cation/anion, has healing properties in a microbiological context.
authors.affiliation: Laboratorio de Biopelículas y Microbiología Ambiental, Centro de Biotecnología, Universidad de Concepción, PO Box 160-C, Concepción, Chile.
authors.forename: Pía
authors.initials: P
authors.lastname: Oyarzúa Alarcón
authors.affiliation: Laboratorio de Biopelículas y Microbiología Ambiental, Centro de Biotecnología, Universidad de Concepción, PO Box 160-C, Concepción, Chile, Facultad de Ciencias Forestales, Universidad de Concepción, PO Box 160-C, Concepción, Chile.
authors.forename: Katherine
authors.initials: K
authors.lastname: Sossa
authors.affiliation: Facultad de Ciencias Químicas, Centro de Biotecnología, Universidad de Concepción, PO Box 160-C, Concepción, Chile.
authors.forename: David
authors.initials: D
authors.lastname: Contreras
authors.affiliation: Laboratorio de Biopelículas y Microbiología Ambiental, Centro de Biotecnología, Universidad de Concepción, PO Box 160-C, Concepción, Chile.
authors.forename: Homero
authors.initials: H
authors.lastname: Urrutia
authors.affiliation: Cranfield Water Science Institute, School of Applied Sciences, Cranfield University, Cranfield, Bedfordshire, MK43 0AL, United Kingdom.
authors.forename: Andreas
authors.initials: A
authors.lastname: Nocker
mesh_terms: D000838:Anions; D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008089:Listeria monocytogenes / Q000187:drug effects* / Q000502:physiology; D015636:Magnesium Chloride / Q000737:chemistry / Q000494:pharmacology*; D010084:Oxidation-Reduction / Q000187:drug effects
chemical_list: D000838:Anions; D000890:Anti-Infective Agents; D015636:Magnesium Chloride
keywords: acid stress; antimicrobial; bacteria; magnesium chloride; pH; sodium chloride