Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida, USA.
Environmental and Biomolecular Systems, Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, Oregon, USA.
J Bacteriol. 2021 Mar 23;203(8). doi: 10.1128/JB.00535-20.
The ability of bacteria, such as the dental pathogen , to coordinate a response against damage-inducing oxidants is a critical aspect of their pathogenicity. The oxidative stress regulator SpxA1 has been demonstrated to be a major player in the ability of to withstand both disulfide and peroxide stresses. While studying spontaneously occurring variants of an Δ strain, we serendipitously discovered that our UA159 host strain bore a single-nucleotide deletion within the coding region of , resulting in a premature truncation of the encoded protein. PerR is a metal-dependent transcriptional repressor that senses and responds to peroxide stress such that loss of PerR activity results in activation of oxidative stress responses. To determine the impact of loss of PerR regulation, we obtained a UA159 isolate bearing an intact copy and created a clean deletion mutant. Our findings indicate that loss of PerR activity results in a strain that is primed to tolerate oxidative stresses in the laboratory setting. Interestingly, RNA deep sequencing (RNA-Seq) and targeted transcriptional expression analyses reveal that PerR offers a minor contribution to the ability of to orchestrate a transcriptional response to peroxide stress. Furthermore, we detected loss-of-function mutations in two other commonly used laboratory strains of , suggesting that this may be not be an uncommon occurrence. This report serves as a cautionary tale regarding the so-called domestication of laboratory strains and advocates for the implementation of more stringent strain authentication practices. A resident of the human oral biofilm, is one of the major bacterial pathogens associated with dental caries. This report highlights a spontaneously occurring mutation within the laboratory strain UA159 found in the coding region of , a gene encoding a transcriptional repressor associated with peroxide tolerance. Though mutant strains of showed a distinct growth advantage and enhanced tolerance toward HO, a Δ deletion strain showed a small number of differentially expressed genes compared to the parent strain, suggesting few direct regulatory targets. In addition to characterizing the role of PerR in , our findings serve as a warning to laboratory researchers regarding bacterial adaptation to growth conditions.
细菌（如口腔病原体）协调抵御损伤诱导氧化剂的能力是其致病性的关键方面。氧化应激调节剂 SpxA1 已被证明是 耐受二硫键和过氧化物应激的主要因素。在研究自发发生的 Δ 菌株变体时，我们偶然发现我们的 UA159 宿主菌株在 的编码区域内发生了单个核苷酸缺失，导致编码蛋白的过早截断。PerR 是一种金属依赖性转录阻遏物，可感应和响应过氧化物应激，因此失去 PerR 活性会导致氧化应激反应的激活。为了确定失去 PerR 调节的影响，我们获得了带有完整 拷贝的 UA159 分离株，并创建了一个清洁的 缺失突变体。我们的研究结果表明，失去 PerR 活性会导致菌株在实验室环境中更容易耐受氧化应激。有趣的是，RNA 深度测序（RNA-Seq）和靶向转录表达分析表明，PerR 对 协调对过氧化物应激的转录反应的能力贡献很小。此外，我们在另外两种常用的实验室 菌株中检测到失活的 突变，这表明这可能不是罕见的情况。本报告提醒人们注意所谓的实验室菌株驯化，并提倡实施更严格的菌株鉴定实践。居住在人类口腔生物膜中的 是与龋齿相关的主要细菌病原体之一。本报告强调了在实验室菌株 UA159 中发现的编码与过氧化物耐受相关的转录阻遏物的 基因的编码区中自发发生的突变。虽然 突变菌株表现出明显的生长优势和对 HO 的增强耐受性，但与亲本菌株相比， Δ 缺失菌株显示出少数差异表达基因，表明很少有直接的调节靶点。除了描述 PerR 在 中的作用外，我们的研究结果还警告实验室研究人员注意细菌对 生长条件的适应。
