Background and aims-It is not known whether lymphocytic colitis and collagenous colitis represent diVerent clinical entities or constitute part of a spectrum of disease. Methods-Detailed clinical features and histological findings were compared in a large series of patients with confirmed lymphocytic and collagenous colitis. Results-Histological diagnosis was confirmed in 96 patients with collagenous colitis and 80 with lymphocytic colitis. Twenty eight per cent of patients with collagenous colitis and 26% of patients with lymphocytic colitis had overlapping but less pronounced histological features. Both groups were equal in terms of age, use of aspirin and non-steroidal antiinflammatory drugs, associated autoimmune conditions, arthritis, diarrhoea, and abdominal pain. The male:female ratio was 27:73 for collagenous colitis and 45:55 for lymphocytic colitis (p=0.013). Twenty five per cent of patients with collagenous colitis compared with 14% of patients with lymphocytic colitis were active smokers; only 8.3% of patients with collagenous colitis had stopped smoking compared with 23% of patients with lymphocytic colitis (p=0.013). Drug induced disease was suspected for ticlopidine (two collagenous colitis, four lymphocytic colitis) and flutamide (four lymphocytic colitis). Mean duration of symptoms before diagnosis was two months for lymphocytic colitis and four months for collagenous colitis. Overall prognosis was generally mild; 84% of patients with lymphocytic colitis and 74% of patients with collagenous colitis reported resolution or significant improvement (p=0.033). Conclusions-Collagenousand lymphocytic colitis are similar but not identical. Patients with lymphocytic colitis present somewhat earlier and are less likely to be active smokers. Symptoms are milder and more likely to disappear in lymphocytic colitis. Ticlopidine and flutamide should be added to the list of drugs inducing colitis. (Gut 1999;45:375-381)

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RNA-binding protein CsrA is a key regulator of a variety of cellular processes in bacteria, including carbon and stationary phase metabolism, biofilm formation, quorum sensing, and virulence gene expression in pathogens. CsrA binds to bipartite sequence elements at or near the ribosome loading site in messenger RNA (mRNA), most often inhibiting translation initiation. Here we describe an alternative novel mechanism through which CsrA achieves negative regulation. We show that CsrA binding to the upstream portion of the 59 untranslated region of Escherichia coli pgaA mRNA-encoding a polysaccharide adhesin export protein-unfolds a secondary structure that sequesters an entry site for transcription termination factor Rho, resulting in the premature stop of transcription. These findings establish a new paradigm for bacterial gene regulation in which remodeling of the nascent transcript by a regulatory protein promotes Rho-dependent transcription attenuation.

Transcription termination factor Rho is a ring-shaped, ATP-dependent molecular motor that targets hundreds of transcription units in Escherichia coli. Interest in Rho was renewed recently on the realization that this essential factor is involved in multiple interactions and cellular processes that protect the E. coli genome and regulate its expression on a global scale. Yet it is currently unknown if (and how) Rho-dependent mechanisms are conserved throughout the bacterial kingdom. Here, we mined public databases to assess the distribution, expression and structural conservation of Rho across bacterial phyla. We found that rho is present in more than 90 % of sequenced bacterial genomes, although Cyanobacteria, Mollicutes and a fraction of Firmicutes are totally devoid of rho. Genomes lacking rho tend to be small and AT-rich and often belong to species with parasitic/symbiotic lifestyles (such as Mollicutes). By contrast, large GCrich genomes, such as those of Actinobacteria, often contain rho duplicates and/or encode Rho proteins that bear insertion domains of unknown function(s). Notwithstanding, most Rho sequences across taxa contain canonical RNA-binding and ATP hydrolysis signature motifs, a feature suggestive of largely conserved mechanism(s) of action. Mutations that impair binding of bicyclomycin are present in~5 % of rho sequences, implying that species from diverse ecosystems have developed resistance against this natural antibiotic. Altogether, these findings assert that Rho function is widespread among bacteria and suggest that it plays a particularly relevant role in the expression of complex genomes and/or bacterial adaptation to changing environments.