Novel Pathways for Ameliorating the Fitness Cost of Gentamicin Resistant Small Colony Variants
Novel Pathways for Ameliorating the Fitness Cost of Gentamicin Resistant Small Colony Variants
复制标题
改善庆大霉素抗性小菌落变体适应成本的新途径
作者：
M. Vestergaard;Wilhelm Paulander;B. Leng;J. Nielsen;H. Westh;H. Ingmer
人类病原体金黄色葡萄球菌的小菌落变体（SCV）与持续感染有关。表型上，SCV的特征在于缓慢生长，并且它们可以在电子传递链中断时出现，从而降低膜电位，从而限制氨基糖苷类（例如，庆大霉素）。在这项研究中，我们研究了SCV的健身成本可以改善的途径。5株S.金黄色葡萄球菌JE2在补充有庆大霉素的琼脂平板上独立选择。SCV在甲基萘醌和氯化血红素生物合成途径中携带突变，这引起相对于野生型（WT; 0.59 - 0.72）的指数生长速率的显著降低和膜电位的降低。50个独立谱系的低健身，耐药突变体连续传代500代或不亚致死浓度的庆大霉素。改进的健身成本遵循三个进化轨迹，并依赖于初始突变类型（点突变与缺失）和传代条件（存在或不存在庆大霉素）。对于在没有庆大霉素的情况下进化的SCV，15个来源于具有点突变的SCV的谱系中有12个获得了密码子内抑制突变，将膜电位、生长速率、庆大霉素敏感性和菌落大小恢复到WT水平。对于携带缺失的SCV，所有谱系增强健身独立的膜电位恢复庆大霉素抗性水平没有改变。通过全基因组测序，我们鉴定了与σ B应激反应相关的基因中的补偿突变（10个谱系中的7个）。编码替代西格玛因子SigB（σ B）的rpoF的失活部分恢复了SCV的适应性。对于在庆大霉素存在下传代的所有谱系，通过膜电位恢复的适应性补偿被抑制，然而，选择用于fusA和SAUSA300_0749中的二次突变。这项研究是第一个描述的健身补偿事件的SCVs与缺失突变和适应的SCVs继续暴露于庆大霉素。
Small colony variants (SCVs) of the human pathogen Staphylococcus aureus are associated with persistent infections. Phenotypically, SCVs are characterized by slow growth and they can arise upon interruption of the electron transport chain that consequently reduce membrane potential and thereby limit uptake of aminoglycosides (e.g., gentamicin). In this study, we have examined the pathways by which the fitness cost of SCVs can be ameliorated. Five gentamicin resistant SCVs derived from S. aureus JE2 were independently selected on agar plates supplemented with gentamicin. The SCVs carried mutations in the menaquinone and hemin biosynthesis pathways, which caused a significant reduction in exponential growth rates relative to wild type (WT; 0.59–0.72) and reduced membrane potentials. Fifty independent lineages of the low-fitness, resistant mutants were serially passaged for up to 500 generations with or without sub-lethal concentrations of gentamicin. Amelioration of the fitness cost followed three evolutionary trajectories and was dependent on the initial mutation type (point mutation vs. deletion) and the passage condition (absence or presence of gentamicin). For SCVs evolved in the absence of gentamicin, 12 out of 15 lineages derived from SCVs with point mutations acquired intra-codonic suppressor mutations restoring membrane potential, growth rate, gentamicin susceptibility and colony size to WT levels. For the SCVs carrying deletions, all lineages enhanced fitness independent of membrane potential restoration without alterations in gentamicin resistance levels. By whole genome sequencing, we identified compensatory mutations in genes related to the σB stress response (7 out of 10 lineages). Inactivation of rpoF that encode for the alternative sigma factor SigB (σB) partially restored fitness of SCVs. For all lineages passaged in the presence of gentamicin, fitness compensation via membrane potential restoration was suppressed, however, selected for secondary mutations in fusA and SAUSA300_0749. This study is the first to describe fitness compensatory events in SCVs with deletion mutations and adaptation of SCVs to continued exposure to gentamicin.
登录
查看更多内容
利福平耐药大肠杆菌的补偿性进化。
影响因子：
3.3
作者：
Reynolds,MG
通讯作者：
Reynolds,MG
细菌的补偿性突变、抗生素耐药性和适应性进化的群体遗传学。
影响因子：
3.3
作者：
Levin,BR;Perrot,V;Walker,N
通讯作者：
Walker,N
影响因子：
2.6
作者：
Baumert, N;Von Eiff, C;Sahl, HG
通讯作者：
Sahl, HG
影响因子：
6.7
作者：
Tuchscherr L;Bischoff M;Lattar SM;Noto Llana M;Pförtner H;Niemann S;Geraci J;Van de Vyver H;Fraunholz MJ;Cheung AL;Herrmann M;Völker U;Sordelli DO;Peters G;Löffler B
通讯作者：
Löffler B