Growth rate control of fumarase (fuma) gene expression in Escherichia coli

Fumarase catalyzes the interconversion of ftimarate and L-malate To study the growth rate control of fumA gene expression in Kscherichia coll, the amount and the stability of fumA mRNA were examined in batch and continuous cultures. With Northern analysis, the amount of fumA mRNA relative to that of total RNA increased fourfold during growth in batch minimal media over the range of growth rates with glucose and acetate as sole carbon sources. In continuous culture, the amount of'fumA mRNA also increased twofold when cell growth rate was changed from I 20/h to 0 72/h. In contrast, the decay of fumA mRNA after blocking the transcriptional initiation with rifampin showed that the stability of fumA mRNA decreased sixfold when the cell growth rate was lowered from 1,20/h to 0.48/h These findings suggested that the growth rate regulation of fumA gene expression was on both transcriptional and post-transcriptional levels.