The presence of mineral fluoride (F⁻) in the environment has both a geogenic and anthropogenic origin, and the halide has been described to be toxic in virtually all living organisms. While the evidence gathered in different microbial species supports this notion, a systematic exploration of the effects of F⁻ salts on the metabolism and physiology of environmental bacteria remained underexplored thus far. In this work, we studied and characterized tolerance mechanisms deployed by the model soil bacterium Pseudomonas putida KT2440 against NaF. By adopting systems-level omic approaches, including functional genomics and metabolomics, we gauged the impact of this anion at different regulatory levels under conditions that impair bacterial growth. Several genes involved in halide tolerance were isolated in a genome-wide Tn-Seq screening—among which crcB, encoding an F⁻-specific exporter, was shown to play the predominant role in detoxification. High-resolution metabolomics, combined with the assessment of intracellular and extracellular pH values and quantitative physiology experiments, underscored the key nodes in central carbon metabolism affected by the presence of F⁻. Taken together, our results indicate that P. putida undergoes a general, multi-level stress response when challenged with NaF that significantly differs from that caused by other saline stressors. While microbial stress responses to saline and oxidative challenges have been extensively studied and described in the literature, very little is known about the impact of fluoride (F⁻) on bacterial physiology and metabolism. This state of affairs contrasts with the fact that F⁻ is more abundant than other halides in the Earth crust (e.g. in some soils, the F⁻ concentration can reach up to 1 mg g_soil⁻¹). Understanding the global effects of NaF treatment on bacterial physiology is not only relevant to unveil distinct mechanisms of detoxification but it could also guide microbial engineering approaches for the target incorporation of fluorine into value-added organofluorine molecules. In this regard, the soil bacterium P. putida constitutes an ideal model to explore such scenarios, since this species is particularly known for its high level of stress resistance against a variety of physicochemical perturbations.

中文翻译：

---

恶臭假单胞菌 CrcB 转运体在氟化物引起的多层次应激反应中的作用

环境中矿物氟化物 (F ^- ) 的存在具有地质成因和人为成因，而且卤化物已被描述为对几乎所有生物体都有毒。虽然在不同微生物物种中收集的证据支持这一观点，但迄今为止，系统探索 F ^-盐对环境细菌的代谢和生理学的影响仍未得到充分探索。在这项工作中，我们研究并描述了模型土壤细菌恶臭假单胞菌部署的耐受机制KT2440 对抗 NaF。通过采用系统级组学方法，包括功能基因组学和代谢组学，我们评估了这种阴离子在损害细菌生长的条件下在不同监管水平上的影响。在全基因组Tn -Seq 筛选中分离出多个涉及卤化物耐受性的基因，其中crcB编码一个 F ^-特异性输出蛋白，显示在解毒中起主要作用。高分辨率代谢组学，结合细胞内和细胞外 pH 值的评估以及定量生理学实验，强调了受 F ^-存在影响的中心碳代谢的关键节点。综上所述，我们的结果表明P。恶臭在受到 NaF 的挑战时会经历一般的、多层次的应激反应，这与其他盐水应激源引起的反应有很大不同。^{虽然微生物对盐水和氧化挑战的应激反应已在文献中进行了广泛研究和描述，但人们对氟化物 (F -} ) 对细菌生理学和新陈代谢的影响知之甚少。这种情况与地壳中 F ^-比其他卤化物更丰富的事实形成对比（例如，在某些土壤中，F ^-浓度可达到 1 mg g_土壤^-1). 了解 NaF 处理对细菌生理学的全球影响不仅与揭示不同的解毒机制有关，而且还可以指导微生物工程方法，以将氟目标掺入增值的有机氟分子中。在这方面，土壤细菌P . 恶臭构成了探索这种情况的理想模型，因为该物种以其对各种物理化学扰动的高水平抗逆性而闻名。