The yicJI metabolic operon of Escherichia coli is involved in bacterial fitness

The yicJI operon of the common genetic backbone of Escherichia coli codes an α-xylosidase and a transporter of the galactosides--pentoses--hexuronides:cation symporter family. In the extraintestinal pathogenic E. coli strain BEN2908, a metabolic operon (frz) of seven genes is found downstream of the yicI gene. It was proved that frz promotes bacterial fitness under stressful conditions. During this work, we identified a motif containing a palindromic sequence in the promoter region of both the frz and the yicJI operons. We then showed that these two operons are cotranscribed, suggesting a functional relationship. The phenotypes of frz and yicJI deletion mutants were compared. Our results showed that although the yicJI operon is not essential for the life of E. coli, it is necessary for its fitness under all the growth conditions tested.