Evaluation of the transcription of small RNA SgrS and glucose transporter mRNA ptsG in E. coli B and E. coli K cultures under high glucose conditions

Escherichia coli is commonly used as the production system for recombinant proteins. However, acetate accumulation in fermentation affects cell growth and protein yield. Recent studies have showed that the small RNA SgrS regulates the major glucose transporter mRNA ptsG in a post–transcriptional manner when the metabolic intermediate glucose–6–phosphate is accumulated intracellularly in E. coli K. Here, comparative analysis of the transcription of SgrS and ptsG is performed between E. coli B and E. coli K cultures in both shake flasks and bioreactor. Both strains expressed SgrS when grown on the non–metabolizable glucose analog α–methyl–glucoside. However, under high glucose conditions, only E. coli B showed significant expression of SgrS. This behavior is unaffected by oxygen supply and pH control. E. coli B produced less acetate on glucose than E. coli K in the bioreactor settings. This provides evidence of a possible connection between SgrS and acetate production in aerobic fermentation of E. coli

Glucose uptake regulation in E. coli by the small RNA SgrS: comparative analysis of E. coli K-12 (JM109 and MG1655) and E. coli B (BL21)

<p>Abstract</p> <p>Background</p> <p>The effect of high glucose concentration on the transcription levels of the small RNA SgrS and the messenger RNA ptsG, (encodin<it>g </it>the glucose transporter IICB^Glc), was studied in both <it>E. coli </it>K-12 (MG1655 and JM109) and <it>E. coli </it>B (BL21). It is known that the transcription level of <it>sgrS </it>increases when <it>E. coli </it>K-12 (MG1655 and JM109) is exposed to the non-metabolized glucose alpha methyl glucoside (αMG) or when the bacteria with a defective glycolysis pathway is grown in presence of glucose. The increased level of sRNA SgrS reduces the level of the ptsG mRNA and consequently lowers the level of the glucose transporter IICB^Glc. The suggested trigger for this action is the accumulation of the corresponding phospho-sugars.</p> <p>Results</p> <p>In the course of the described work, it was found that <it>E. coli </it>B (BL21) and <it>E. coli </it>K-12 (JM109 and MG1655) responded similarly to αMG: both strains increased <it>SgrS </it>transcription and reduced <it>ptsG </it>transcription. However, the two strains reacted differently to high glucose concentration (40 g/L). <it>E. coli </it>B (BL21) reacted by increasing <it>sgrS </it>transcription and reducing <it>ptsG </it>transcription while <it>E. coli </it>K-12 (JM109 and MG1655) did not respond to the high glucose concentration, and, therefore, transcription of <it>sgrS </it>was not detected and ptsG mRNA level was not affected.</p> <p>Conclusions</p> <p>The results suggest that <it>E. coli </it>B (BL21) tolerates high glucose concentration not only by its more efficient central carbon metabolism, but also by controlling the glucose transport into the cells regulated by the sRNA SgrS, which may suggest a way to control glucose consumption and increase its efficient utilization.</p

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead