Group 2 Sigma Factor SigB of Corynebacterium glutamicum Positively Regulates Glucose Metabolism under Conditions of Oxygen Deprivation

The sigB gene of Corynebacterium glutamicum encodes a group 2 sigma factor of RNA polymerase. Under conditions of oxygen deprivation, the sigB gene is upregulated and cells exhibit high productivity of organic acids as a result of an elevated glucose consumption rate. Using DNA microarray and quantitative reverse transcription-PCR (RT-PCR) analyses, we found that sigB disruption led to reduced transcript levels of genes involved in the metabolism of glucose into organic acids. This in turn resulted in retardation of glucose consumption by cells under conditions of oxygen deprivation. These results indicate that SigB is involved in positive regulation of glucose metabolism genes and enhances glucose consumption under conditions of oxygen deprivation. Moreover, sigB disruption reduced the transcript levels of genes involved in various cellular functions, including the glucose metabolism genes not only in the growth-arrested cells under conditions of oxygen deprivation but also in the cells during aerobic exponential growth, suggesting that SigB functions as another vegetative sigma factor.