The Functional Characterization of the 6-Phosphogluconate Dehydratase Operon in 2-Ketogluconic Acid Industrial Producing Strain Pseudomonas plecoglossicida JUIM01

Genus <i>Pseudomonas</i> bacteria mainly consume glucose through the Entner-Doudoroff (ED) route due to a lack of a functional Embden-Meyerhof-Parnas (EMP) pathway. In the present study, a 6-phosphogluconate dehydratase (<i>edd</i>) operon in the ED route was well investigated to find its structural characteristics and roles in the regulation of glucose consumption and 2-ketogluconic acid (2KGA) metabolism in the industrial 2KGA-producer <i>P. plecoglossicida</i> JUIM01. The <i>edd</i> operon contained four structural genes of <i>edd</i>, <i>glk</i>, <i>gltR</i>, and <i>gtrS</i>, encoding 6-PG dehydratase Edd, glucokinase Glk, response regulatory factor GltR, and histidine kinase GtrS, respectively. A promoter region was observed in the 5'-upstream of the <i>edd</i> gene, with a transcriptional start site located 129 bp upstream of the <i>edd</i> gene and in a pseudo-palindromic sequence of 5'-TTGTN₇ACAA-3' specifically binding to the transcription factor HexR. The knockout of the <i>edd</i> gene showed a remarkably negative effect on cell growth and re-growth using 2KGA as a substrate, beneficial to 2KGA production, with an increase of 8%. The deletion of <i>glk</i> had no significant effect on the cell growth or glucose metabolism, while showing an adverse impact on the 2KGA production, with a decrease of 5%. The outputs of the present study would provide a theoretical basis for 2KGA-producer improvement with metabolic engineering strategies and the development and optimization of <i>P. plecoglossicida</i> as the chassis cells.