A Q-like transcription factor regulates biofilm development in Escherichia coli by controlling expression of the DLP12 lysis cassette Rueggeberg, Karl-Gustav and Toba, Faustino A. and Thompson, Mitchell G. and Campbell, Bryan R. and Hay, Anthony G.,, 159, 691-700 (2013), doi = https://doi.org/10.1099/mic.0.064741-0, publicationName = Microbiology Society, issn = 1350-0872, abstract= The DLP12 lysis cassette (essD, ybcT, rzpD/rzoD) is required in certain Escherichia coli strains for normal curli expression and biofilm development. Tightly controlled regulation of the lysis cassette is of particular importance, since its overexpression causes host cell lysis. In silico analysis revealed a putative intrinsic transcriptional terminator 100 bp upstream of essD and within 2000 bp of ybcQ (QDLP12 ), a putative lambda (λ) Q-like antiterminator. We hypothesized that QDLP12 may be required for effective expression of the lysis cassette. In this work we report on the role of QDLP12 as a positive regulator of DLP12 lysis cassette expression. Mutants lacking QDLP12 exhibited a biofilm-defective phenotype analogous to that of the lysis cassette knockouts. This defect occurred through the downregulation of curli transcription, which is also consistent with that seen in the lysis cassette mutants and was restored by complementation by ectopic expression of QDLP12 . In addition, QDLP12 overexpression caused cell lysis, as demonstrated by leakage of β-galactosidase activity from cells. This was accompanied by upregulation of the DLP12 lysis cassette as demonstrated by increased essD transcription, which was documented with gfp-reporter assays, RT-PCR and chromatin immunoprecipitation (ChIP). We provide evidence that this Q-mediated effect resulted from direct interaction of QDLP12 with the lysis cassette promoter (essDp), as demonstrated by electrophoretic gel mobility shift assay (EMSA). We propose that QDLP12 encodes a functional transcriptional regulator, which promotes expression of the DLP12 lysis cassette. This work provides evidence of a regulator from a defective prophage affecting host cell physiology., language=, type=