Environmental Factors in the Relapse and Recurrence of Inflammatory Bowel Disease:A Review of the Literature

The causes of relapse in patients with Crohn's disease (CD) and ulcerative colitis (UC) are largely unknown. This paper reviews the epidemiological and clinical data on how medications (non-steroidal anti-inflammatory drugs, estrogens and antibiotics), lifestyle factors (smoking, psychological stress, diet and air pollution) may precipitate clinical relapses and recurrence. Potential biological mechanisms include: increasing thrombotic tendency, imbalances in prostaglandin synthesis, alterations in the composition of gut microbiota, and mucosal damage causing increased permeability

A coiled-coil domain acts as a molecular ruler to regulate O-antigen chain length in lipopolysaccharide

Long-chain bacterial polysaccharides have important roles in pathogenicity. In Escherichia coli O9a, a model for ABC transporter–dependent polysaccharide assembly, a large extracellular carbohydrate with a narrow size distribution is polymerized from monosaccharides by a complex of two proteins, ​WbdA (polymerase) and ​WbdD (terminating protein). Combining crystallography and small-angle X-ray scattering, we found that the C-terminal domain of ​WbdD contains an extended coiled-coil that physically separates ​WbdA from the catalytic domain of ​WbdD. The effects of insertions and deletions in the coiled-coil region were analyzed in vivo, revealing that polymer size is controlled by varying the length of the coiled-coil domain. Thus, the coiled-coil domain of ​WbdD functions as a molecular ruler that, along with ​WbdA:​WbdD stoichiometry, controls the chain length of a model bacterial polysaccharide