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Controlling biofilm formation, prophage excision and cell death by rewiring global regulator H-NS of Escherichia coli.

ABSTRACT: The global regulator H-NS of Escherichia coli controls genes related to stress response, biofilm formation and virulence by recognizing curved DNA and by silencing acquired genes. Here, we rewired H-NS to control biofilm formation using protein engineering; H-NS variant K57N was obtained that reduces biofilm formation 10-fold compared with wild-type H-NS (wild-type H-NS increases biofilm formation whereas H-NS K57N reduces it). Whole-transcriptome analysis revealed that H-NS K57N represses biofilm formation through its interaction with the nucleoid-associated proteins Cnu and StpA and in the absence of these proteins, H-NS K57N was unable to reduce biofilm formation. Significantly, H-NS K57N enhanced the excision of defective prophage Rac while wild-type H-NS represses excision, and H-NS controlled only Rac excision among the nine resident E. coli K-12 prophages. Rac prophage excision not only led to the change in biofilm formation but also resulted in cell lysis through the expression of toxin HokD. Hence, the H-NS regulatory system may be evolved through a single-amino-acid change in its N-terminal oligomerization domain to control biofilm formation, prophage excision and apoptosis.

SUBMITTER: Hong SH

PROVIDER: S-EPMC3158429 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Identification of a novel prophage regulator in Escherichia coli controlling the expression of type III secretion.

Project description:This study has identified horizontally acquired genomic regions of enterohaemorrhagic Escherichia coli O157:H7 that regulate expression of the type III secretion (T3S) system encoded by the locus of enterocyte effacement (LEE). Deletion of O-island 51, a 14.93 kb cryptic prophage (CP-933C), resulted in a reduction in LEE expression and T3S. The deletion also had a reduced capacity to attach to epithelial cells and significantly reduced E. coli O157 excretion levels from sheep. Further characterization of O-island 51 identified a novel positive regulator of the LEE, encoded by ecs1581 in the E. coli O157:H7 strain Sakai genome and present but not annotated in the E. coli strain EDL933 sequence. Functionally important residues of ECs1581 were identified based on phenotypic variants present in sequenced E. coli strains and the regulator was termed RgdR based on a motif demonstrated to be important for stimulation of gene expression. While RgdR activated expression from the LEE1 promoter in the presence or absence of the LEE-encoded regulator (Ler), RgdR stimulation of T3S required ler and Ler autoregulation. RgdR also controlled the expression of other phenotypes, including motility, indicating that this new family of regulators may have a more global role in E. coli gene expression.

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