Vincent Maxence S, Vergnes Alexandra, Ezraty Benjamin
Aix-Marseille Université, CNRS, Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, Marseille, France.
Microbiol Spectr. 2023 Feb 8;11(2):e0499122. doi: 10.1128/spectrum.04991-22.
Under anaerobic conditions, chlorate is reduced to chlorite, a cytotoxic compound that triggers oxidative stress within bacterial cultures. We previously found that BD Bacto Casamino Acids were contaminated with chlorate. In this study, we investigated whether chlorate contamination is detectable in other commercial culture media. We provide evidence that in addition to different batches of BD Bacto Casamino Acids, several commercial agar powders are contaminated with chlorate. A direct consequence of this contamination is that, during anaerobic growth, Escherichia coli cells activate the expression of , a gene encoding periplasmic methionine sulfoxide reductase, which repairs oxidized protein-bound methionine. We further demonstrate that during aerobic growth, progressive oxygen depletion triggers expression in a subpopulation of cells due to the presence of chlorate. Hence, we propose that chlorate contamination in commercial growth media is a source of phenotypic heterogeneity within bacterial populations. Agar is arguably the most utilized solidifying agent for microbiological media. In this study, we show that agar powders from different suppliers, as well as certain batches of BD Bacto Casamino Acids, contain significant levels of chlorate. We demonstrate that this contamination induces the expression of a methionine sulfoxide reductase, suggesting the presence of intracellular oxidative damage. Our results should alert the microbiology community to a pitfall in the cultivation of microorganisms under laboratory conditions.
在厌氧条件下，氯酸盐会被还原为亚氯酸盐，这是一种细胞毒性化合物，会在细菌培养物中引发氧化应激。我们之前发现BD Bacto酪蛋白氨基酸被氯酸盐污染。在本研究中，我们调查了其他商业培养基中是否可检测到氯酸盐污染。我们提供的证据表明，除了不同批次的BD Bacto酪蛋白氨基酸外，几种商业琼脂粉也被氯酸盐污染。这种污染的直接后果是，在厌氧生长期间，大肠杆菌细胞会激活编码周质甲硫氨酸亚砜还原酶的基因的表达，该酶可修复氧化的蛋白质结合甲硫氨酸。我们进一步证明，在有氧生长期间，由于氯酸盐的存在，逐渐的氧气消耗会触发细胞亚群中的基因表达。因此，我们提出商业生长培养基中的氯酸盐污染是细菌群体中表型异质性的一个来源。琼脂可以说是微生物培养基中使用最广泛的凝固剂。在本研究中，我们表明来自不同供应商的琼脂粉以及某些批次的BD Bacto酪蛋白氨基酸含有大量氯酸盐。我们证明这种污染会诱导甲硫氨酸亚砜还原酶的表达，表明存在细胞内氧化损伤。我们的结果应提醒微生物学界注意实验室条件下微生物培养中的一个陷阱。
