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FEMS Microbiol Lett. 2003 Sep 26;226(2):245-9.

beta-Lactam induction of colanic acid gene expression in Escherichia coli.

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Department of Microbiology and Immunology, University of North Dakota School of Medicine, Grand Forks, ND 58202-9037, USA.


An unexpected observation led us to examine the relationship between beta-lactam exposure and synthesis of colonic acid capsular polysaccharide in Escherichia coli. Strains containing a cps-lacZ transcriptional fusion were challenged with antibiotics having various modes of action, and gene expression was detected by a disk-diffusion assay and in broth cultures. The cps genes were induced by a subset of beta-lactams but not by agents inhibiting protein synthesis or DNA replication, indicating that cps expression was specific and not due to stresses accompanying cell death or by a general inhibition of peptidoglycan synthesis. A narrow concentration just below the MIC triggered cps expression in liquid culture, suggesting the response may be triggered by near-lethal levels of antibiotic. Because colanic acid is important for maturation of biofilm architecture, antibiotics that increase its synthesis might exacerbate the formation or persistence of biofilms.

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