We propose a mechanism of action for the betL* mutation which is based on DNA topology. Removing a single thymine residue from the betL σA promoter's −10 and −35 spacer results in a ‘twist’-mediated activation of transcription which accounts for the osmotolerance phenotype observed for strains expressing betL*.
Keane, S. M., Culligan, E. P., Hoffmann, R. F., Gahan, C. G. M., Hill, C., Snelling, W. J., & Sleator, R. D. (2016). Shedding light on betL*: pPL2-lux mediated real-time analysis of betL* expression in Listeria monocytogenes. Bioengineered, 7(2), 116-119. https://doi.org/10.1080/21655979.2016.1171438