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Wild‐type Escherichia coli MG1655 usually does not accumulate l‐threonine. In this study, the effects of 13 genes related to the glucose uptake, glycolysis, TCA cycle, l‐threonine biosynthesis, or their regulation on l‐threonine accumulation in E. coli MG1655 were investigated. Sixteen E. coli mutant strains were constructed by chromosomal deletion or overexpression of one or more genes of rsd, ptsG, ptsH, ptsI, crr, galP, glk, iclR, and gltA; the plasmid pFW01‐thrA*BC‐rhtC harboring the key genes for l‐threonine biosynthesis and secretion was introduced into these mutants. The analyses on cell growth, glucose consumption, and l‐threonine production of these recombinant strains showed that most of these strains could accumulate l‐threonine, and the highest yield was obtained in WMZ016/pFW01‐thrA*BC‐rhtC. WMZ016 was derived from MG1655 by deleting crr and iclR and enhancing the expression of gltA. WMZ016/pFW01‐thrA*BC‐rhtC could produce 17.98 g/L l‐threonine with a yield of 0.346 g/g glucose, whereas the control strain MG1655/pFW01‐thrA*BC‐rhtC could only produce 0.68 g/L l‐threonine. In addition, WMZ016/pFW01‐thrA*BC‐rhtC could tolerate the high concentration of glucose and produced no detectable by‐products; therefore, it should be an ideal platform strain for further development. The results indicate that manipulating the glucose uptake and TCA cycle could efficiently increase l‐threonine production in E. coli.

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BackgroundRecent evidence has shown that long noncoding RNAs (lncRNAs) are involved in the process of epithelial-mesenchymal transition (EMT). However, little research has focused on the expression profile of lncRNAs during EMT in human lens epithelial cells (LECs) and their functions have not yet been described.MethodsDysregulated lncRNAs and mRNAs in normal human lens epithelial B-3(HLE B-3) cells and during transforming growth factor β2(TGF-β2)-induced EMT were analyzed via lncRNA microarray. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway analyses of differentially expressed mRNAs were performed to identify their functions and pathologic pathways. Six candidate lncRNAs were validated via quantitative real-time reverse transcription polymerase chain reaction(qRT-PCR) to confirm the microarray data.ResultsA total of 775 lncRNAs (325 up-regulated and 450 down-regulated) and 935 mRNAs (329 up-regulated and 606 down-regulated) were differentially expressed in HLE B-3 cells during TGF-β2-induced EMT compared to normal HLE B-3 cells. GO and KEGG Pathway analyses indicated the functions of differentially expressed mRNAs in the TGF-β2-induced EMT in HLE B-3 cells. qRT-PCR confirmed the trends indicated in microarray analysis for all 6 candidate lncRNAs.ConclusionOur study lays the foundation for future research in lncRNAs related to EMT in HLE B-3 cells and could provide new avenues for the prevention and treatment of posterior capsule opacification (PCO).