When exposed to the nonmetabolized glucose derivative alpha methyl glucoside (αMG), both Escherichia coli K-12 (JM109 and MG1655) and E. coli B (BL21) respond by reducing the concentration of the mRNA of the ptsG gene which is responsible for the biosynthesis of the glucose transporter EIICB(glu). This occurs through the over-expression of the noncoding small RNA SgrS, which interacts specifically with the mRNA of the ptsG gene and prevents its translation. However, when these bacteria are exposed to a glucose concentration of 40 g/L, over-expression of SgrS is observed only in E. coli B (BL21). Unlike E. coli K-12 (JM109 and MG1655), which are affected by high glucose concentration and produce higher levels of acetate, E. coli B (BL21) is not affected. Based on this information, it was assumed that over-expression of SgrS enables E. coli B (BL21) to reduce its acetate excretion by controlling the glucose transport. When SgrS was over-expressed in both E. coli K-12 strains from a multicopy plasmid, it was possible to reduce their acetate excretion levels to those seen in E. coli B. This observation opens a new approach towards controlling bacterial metabolism through the use of noncoding RNA.

中文翻译：

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通过过表达小 RNA SgrS 减少大肠杆菌 K-12 的醋酸盐排泄

当暴露于非代谢葡萄糖衍生物 α 甲基葡糖苷 (αMG) 时，大肠杆菌 K-12（JM109 和 MG1655）和大肠杆菌 B（BL21）都会通过降低 ptsG 基因的 mRNA 浓度做出反应，该基因负责葡萄糖转运蛋白 EIICB(glu) 的生物合成。这是通过非编码小 RNA SgrS 的过度表达而发生的，SgrS 与 ptsG 基因的 mRNA 特异性相互作用并阻止其翻译。然而，当这些细菌暴露于 40 g/L 的葡萄糖浓度时，仅在大肠杆菌 B (BL21) 中观察到 SgrS 的过度表达。与大肠杆菌 K-12（JM109 和 MG1655）不同，后者受高葡萄糖浓度影响并产生更高水平的醋酸盐，而大肠杆菌 B（BL21）不受影响。基于此信息，假设 SgrS 的过度表达使 E. 大肠杆菌 B (BL21) 通过控制葡萄糖转运来减少其醋酸盐排泄。当 SgrS 在来自多拷贝质粒的两种大肠杆菌 K-12 菌株中过表达时，有可能将它们的醋酸盐排泄水平降低到大肠杆菌B 中的水平。这一观察结果开辟了一种通过以下方式控制细菌代谢的新方法非编码RNA的使用。