Background: Bacterial transcription attenuation occurs through a variety of cis-regulatory elements that controlgene expression in response to a wide range of signals. The signal-sensing structures in attenuators are so diverseand rapidly evolving that only a small fraction have been properly annotated and characterized to date. Here weapply a broad-spectrum detection tool in order to achieve a more complete view of the transcriptional attenuationcomplement of key bacterial species. Results: Our protocol seeks gene families with an unusual frequency of 5’ terminators found across multiple species. Many of the detected attenuators are part of annotated elements, such as riboswitches or T-boxes, which often operate through transcriptional attenuation. However, a significant fraction of candidates were not previously characterized in spite of their unmistakable footprint. We further characterized some of these new elements usingsequence and secondary structure analysis. We also present elements that may control the expression of severalnon-homologous genes, suggesting co-transcription and response to common signals. An important class of suchelements, which we called mobile attenuators, is provided by 3’ terminators of insertion sequences or prophagesthat may be exapted as 5’ regulators when inserted directly upstream of a cellular gene. Conclusions: We show here that attenuators involve a complex landscape of signal-detection structures spanningthe entire bacterial domain. We discuss possible scenarios through which these diverse 5’ regulatory structures mayarise or evolve.
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