Schenk Emily R, Nau Frederic, Thompson Christopher J, Tse-Dinh Yuk-Ching, Fernandez-Lima Francisco
Department of Chemistry and Biochemistry, Florida International University, Miami, FL, 33199, USA.
J Mass Spectrom. 2015 Jan;50(1):88-94. doi: 10.1002/jms.3500.
Bacterial resistance to antibiotics has become an increasing threat, requiring not only the development of new targets in drug discovery, but more importantly, a better understanding of cellular response. In the current study, three closely related Escherichia coli strains, a wild type (MG1655) and an isogenic pair derived from the wild type (DPB635 and DPB636) are studied following exposure to sub lethal concentrations of antibiotic (norfloxacin) over time. In particular, genotype similarities between the three strains were assessed based on the lipid regulation response (e.g. presence/absence and up/down regulation). Lipid identification was performed using direct surface probe analysis (matrix-assisted laser desorption/ionization, MALDI), coupled to high-resolution mass spectrometry (Fourier transform ion cyclotron resonance mass spectrometry, FT-ICR MS) followed by statistical analysis of variability and reproducibility across batches using internal standards. Inspection of the lipid profile showed that for the MG1655, DPB635 and DPB636 E. coli strains, a similar distribution of the altered lipids was observed after exposure to norfloxacin antibiotic (e.g. fatty acids and glycerol phospholipids are up and down regulated, respectively). Additionally, variations in the lipid distribution resemble the extent to which each strain can combat the antibiotic exposure. That is, the topA66 topoisomerase I mutation of DPB636 translates into diminished response related to antibiotic sensitivity when compared to MG1655 and the DPB635 strains.
细菌对抗生素的耐药性已成为日益严重的威胁，这不仅需要在药物研发中开发新的靶点，更重要的是，要更好地了解细胞反应。在当前的研究中，对三种密切相关的大肠杆菌菌株进行了研究，一种是野生型（MG1655），另外两种是源自野生型的同基因菌株（DPB635和DPB636），研究它们在一段时间内暴露于亚致死浓度的抗生素（诺氟沙星）后的情况。特别是，基于脂质调节反应（例如存在/不存在以及上调/下调）评估了这三种菌株之间的基因型相似性。使用直接表面探针分析（基质辅助激光解吸/电离，MALDI）结合高分辨率质谱（傅里叶变换离子回旋共振质谱，FT-ICR MS）进行脂质鉴定，随后使用内标对批次间的变异性和重现性进行统计分析。脂质谱检查表明，对于MG1655、DPB635和DPB636大肠杆菌菌株，在暴露于诺氟沙星抗生素后，观察到脂质变化的分布相似（例如脂肪酸和甘油磷脂分别上调和下调）。此外，脂质分布的变化类似于每种菌株对抗生素暴露的抵抗程度。也就是说，与MG1655和DPB635菌株相比，DPB636的topA66拓扑异构酶I突变导致与抗生素敏感性相关的反应减弱。
