Investigation of ptsG gene in response to xylose utilization in Corynebacterium glutamicum.

Corynebacterium glutamicum strains NC-2 were able to grow on xylose as sole carbon sources in our previous work. Nevertheless, it exhibited the major shortcoming that the xylose consumption was repressed in the presence of glucose. So far, regarding C. glutamicum, there are a number of reports on ptsG gene, the glucose-specific transporter, involved in glucose metabolism. Recently, we found ptsG had influence on xylose utilization and investigated the ptsG gene in response to xylose utilization in C. glutamicum with the aim to improve xylose consumption and simultaneously utilized glucose and xylose. The ptsG-deficient mutant could grow on xylose, while exhibiting noticeably reduced growth on xylose as sole carbon source. A mutant deficient in ptsH, a general PTS gene, exhibited a similar phenomenon. When complementing ptsG gene, the mutant ΔptsG-ptsG restored the ability to grow on xylose similarly to NC-2. These indicate that ptsG gene is not only essential for metabolism on glucose but also important in xylose utilization. A ptsG-overexpressing recombinant strain could not accelerate glucose or xylose metabolism. When strains were aerobically cultured in a sugar mixture of glucose and xylose, glucose and xylose could not be utilized simultaneously. Interestingly, the ΔptsG strain could co-utilize glucose and xylose under oxygen-deprived conditions, though the consumption rate of glucose and xylose dramatically declined. It was the first report of ptsG gene in response to xylose utilization in C. glutamicum.