Enterococcus faecalis OG1RF Evolution at Low pH Selects Fusidate-Sensitive Mutants in Elongation Factor G and at High pH Selects Defects in Phosphate Transport
Enterococcus faecalis OG1RF Evolution at Low pH Selects Fusidate-Sensitive Mutants in Elongation Factor G and at High pH Selects Defects in Phosphate Transport
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DOI：
10.1128/aem.00466-23
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发表时间：
2023-03
影响因子：
4.4
通讯作者：
Bailey A. Fitzgerald;A. Wadud;Zachary C. Slimak;J. Slonczewski
中科院分区：
文献类型：
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作者：
Bailey A. Fitzgerald;A. Wadud;Zachary C. Slimak;J. Slonczewski
E.在牙齿生物膜中发现了粪细菌，在那里它们由于发酵代谢而经历低pH。因此，pH对抗生素耐药性的影响具有临床意义。摘要肠球菌属细菌栖息于pH值范围很广的人类和土壤环境中。菌株包括细菌以及耐药性病原体。研究了E.通过在酸性（pH 4.8）、中性pH（pH 7.0）和碱性（pH 9.0）条件下进行实验进化，对粪肠球菌OG 1 RF进行了研究。进行500代的连续无菌培养，并在高pH生物膜培养中进行4次连续珠转移。几乎所有的突变导致非同义密码子，表明适应性选择。所有的酸适应的克隆从嗜酸性培养物中表现出突变的fusA（编码延伸因子G）。酸适应的fusA突变体具有对夫西地酸（夫西地酸）的抗性降低的权衡。所有的碱基适应的克隆，以及一些从适应的生物膜培养物显示突变，影响Pst磷酸ABC转运蛋白（pstA，pstB，pstB 2，pstC）和pyrR（嘧啶生物合成调节/尿嘧啶磷酸核糖转移酶）。生物膜培养物在脑心浸液琼脂上产生小尺寸菌落。这些变体各自在pstB 2、pstC或pyrR中含有单个突变。pst和pyrR突变体在pH 9.2下生长超过祖先菌株，在pH 4.8下生长较低。在高pH下进化的多个克隆中具有突变的其他基因（但不在低pH下）包括opp 1BCDF（寡肽ABC转运蛋白），ccpA（分解代谢物控制蛋白A）和ftsZ（分隔蛋白）。总体而言，E. faecalis表现出强烈的pH依赖性，有利于在低pH下对呋塞米酸敏感的延伸因子G的修饰和在高pH下磷酸盐转运基因的丧失。在牙齿生物膜中发现了粪细菌，在那里它们由于发酵代谢而经历低pH。因此，pH对抗生素耐药性的影响具有临床意义。对于OG 1 RF菌株而言，夫西地酸盐耐药性的丧失是值得注意的，其中假定夫西地酸盐耐药性是稳定的遗传标记。在牙髓感染中，肠球菌可以抵抗产生极高pH值的氢氧化钙治疗。在其他环境中，如土壤和植物根际，肠球菌经历与气候变化相关的酸化。因此，肠球菌自然选择的pH调节对人类健康以及了解土壤环境都很重要。
E. faecalis bacteria are found in dental biofilms, where they experience low pH as a result of fermentative metabolism. Thus, the effect of pH on antibiotic resistance has clinical importance. ABSTRACT Enterococcus bacteria inhabit human and soil environments that show a wide range of pH values. Strains include commensals as well as antibiotic-resistant pathogens. We investigated the adaptation to pH stress in E. faecalis OG1RF by conducting experimental evolution under acidic (pH 4.8), neutral pH (pH 7.0), and basic (pH 9.0) conditions. A serial planktonic culture was performed for 500 generations and in a high-pH biofilm culture for 4 serial bead transfers. Nearly all of the mutations led to nonsynonomous codons, indicating adaptive selection. All of the acid-adapted clones from the planktonic culture showed a mutation in fusA (encoding elongation factor G). The acid-adapted fusA mutants had a trade-off of decreased resistance to fusidic acid (fusidate). All of the base-adapted clones from the planktonic cultures as well as some from the biofilm-adapted cultures showed mutations that affected the Pst phosphate ABC transporter (pstA, pstB, pstB2, pstC) and pyrR (pyrimidine biosynthesis regulator/uracil phosphoribosyltransferase). The biofilm cultures produced small-size colonies on brain heart infusion agar. These variants each contained a single mutation in pstB2, pstC, or pyrR. The pst and pyrR mutants outgrew the ancestral strain at pH 9.2, with a trade-off of lower growth at pH 4.8. Additional genes that had a mutation in multiple clones that evolved at high pH (but not at low pH) include opp1BCDF (oligopeptide ABC transporter), ccpA (catabolite control protein A), and ftsZ (septation protein). Overall, the experimental evolution of E. faecalis showed a strong pH dependence, favoring the fusidate-sensitive elongation factor G modification at low pH and the loss of phosphate transport genes at high pH. IMPORTANCE E. faecalis bacteria are found in dental biofilms, where they experience low pH as a result of fermentative metabolism. Thus, the effect of pH on antibiotic resistance has clinical importance. The loss of fusidate resistance is notable for OG1RF strains in which fusidate resistance is assumed to be a stable genetic marker. In endodontal infections, enterococci can resist calcium hydroxide therapy that generates extremely high pH values. In other environments, such as the soil and plant rhizosphere, enterococci experience acidification that is associated with climate change. Thus, the pH modulation of natural selection in enterococci is important for human health as well as for understanding soil environments.