Oyarzúa Alarcón Pía, Sossa Katherine, Contreras David, Urrutia Homero, Nocker Andreas
Laboratorio de Biopelículas y Microbiología Ambiental, Centro de Biotecnología, Universidad de Concepción, PO Box 160-C, Concepción, Chile.
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.
Magnes Res. 2014 Apr-Jun;27(2):57-68. doi: 10.1684/mrh.2014.0362.
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.
镁是生命必需的元素，普遍存在于所有生物体中。不同的阳离子作为酶的辅助因子、信号分子以及在稳定细胞成分方面发挥着重要作用。微生物学实验中镁盐通常具有积极作用也就不足为奇了。在本研究中，以单核细胞增生李斯特菌作为模式生物，然而我们关注的是镁（以MgCl2的形式）作为应激增强剂的效用。虽然MgCl2在近中性pH值下不影响细菌活力，但当细胞悬液在酸性pH值下暴露于该盐时，发现它会严重损害可培养性和氧化还原活性。这一原理在许多革兰氏阴性菌和革兰氏阳性菌中得到了证实。镁盐显著提高了酸度，在存在磷酸根、乳酸根或醋酸根等阴离子碱（但不是TRIS）的情况下达到了抗菌水平。MgCl2的抗菌活性比NaCl、KCl或CaCl2强得多。MgSO4没有效果，或者当细胞在pH≥5的磷酸盐缓冲液中暴露于MgCl2时也没有效果。MgCl2对微生物活力还有一种额外的、盐特异性的影响，这种影响会增强酸应激，需要进一步研究。除了对表面消毒的影响外，这一观察结果可能支持了MgCl2治疗皮肤病（健康皮肤是酸性环境）的常见治疗特性，并有助于理解为什么死海的盐（其中Mg(2+)和Cl(-)是最丰富的阳离子/阴离子）在微生物学背景下具有治疗特性。
