In order to investigate the interaction of well-known regulation systems, quorum sensing and stringent response for the expression of virulence genes in enterohemorrhagic Escherichia coli (EHEC), E. coli strains with mutations in the two regulation systems, ΔluxS (ECM101) and ΔluxSΔrelAΔspoT (ECM201), and ΔluxS complemented strain to ECM201 (ECM202) were created from EHEC O157:H7 EDL933. Phenotypic characterization revealed that mutations in the stringent response system (ECM201 and ECM202) influenced the metabolic (defective utilization of arabinose and L-sorbose), enzymatic activities (decreased trypsin activity, and increased α-glucosidase activity) and motility. Our results suggest that quorum sensing interacts with stringent response regulation system.