Lee Chin How, Oon Jack S H, Lee Kun Cheng, Ling Maurice H T
School of Chemical and Life Sciences, Singapore Polytechnic, Singapore 139651, Singapore.
ISRN Microbiol. 2012 Mar 5;2012:965356. doi: 10.5402/2012/965356. Print 2012.
Escherichia coli is commonly found in intestine of human, and any changes in their adaptation or evolution may affect the human body. The relationship between E. coli and food additives is less studied as compared to antibiotics. E. coli within our human gut are consistently interacting with the food additives; thus, it is important to investigate this relationship. In this paper, we observed the evolution of E. coli cultured in different concentration of food additives (sodium chloride, benzoic acid, and monosodium glutamate), singly or in combination, over 70 passages. Adaptability over time was estimated by generation time and cell density at stationary phase. Polymerase chain reaction (PCR)/restriction fragments length polymorphism (RFLP) using 3 primers and restriction endonucleases, each was used to characterize adaptation/evolution at genomic level. The amplification and digestion profiles were tabulated and analyzed by Nei-Li dissimilarity index. Our results demonstrate that E. coli in every treatment had adapted over 465 generations. The types of stress were discovered to be different even though different concentrations of same additives were used. However, RFLP shows a convergence of genetic distances, suggesting the presence of global stress response. In addition, monosodium glutamate may be a nutrient source and support acid resistance in E. coli.
大肠杆菌常见于人类肠道中，其适应性或进化的任何变化都可能影响人体。与抗生素相比，对大肠杆菌与食品添加剂之间关系的研究较少。我们人类肠道内的大肠杆菌一直在与食品添加剂相互作用；因此，研究这种关系很重要。在本文中，我们观察了在不同浓度的食品添加剂（氯化钠、苯甲酸和味精）单独或组合作用下培养70代的大肠杆菌的进化情况。通过世代时间和稳定期的细胞密度来评估随时间的适应性。使用3种引物和限制性内切酶的聚合酶链反应（PCR）/限制性片段长度多态性（RFLP），每种方法都用于在基因组水平上表征适应性/进化。通过Nei-Li差异指数对扩增和消化图谱进行列表和分析。我们的结果表明，每种处理中的大肠杆菌在465代后都发生了适应。即使使用相同添加剂的不同浓度，发现应激类型也不同。然而，RFLP显示遗传距离趋同，表明存在全局应激反应。此外，味精可能是一种营养源，并支持大肠杆菌的耐酸性。
