Increased adherence and actin pedestal formation by dam-deficient enterohaemorrhagic Escherichia coli O157:H7
Graduate School of Biomedical Sciences; Department of Molecular Genetics and Microbiology
Medical Subject Headings
Actins; Adhesins, Bacterial; Animals; Artificial Gene Fusion; *Bacterial Adhesion; Carrier Proteins; Disease Models, Animal; Escherichia coli Infections; Escherichia coli O157; Escherichia coli Proteins; *Gene Deletion; Gene Expression Regulation, Bacterial; Genes, Reporter; Green Fluorescent Proteins; Hela Cells; Humans; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; Oligonucleotide Array Sequence Analysis; RNA, Bacterial; RNA, Messenger; Receptors, Cell Surface; Reverse Transcriptase Polymerase Chain Reaction; Site-Specific DNA-Methyltransferase; (Adenine-Specific); Swine; Transcription, Genetic
Life Sciences | Medicine and Health Sciences
Enterohaemorrhagic Escherichia coli (EHEC) are highly infectious pathogens capable of causing severe diarrhoeal illnesses. As a critical step during their colonization, EHEC adhere intimately to intestinal epithelial cells and generate F-actin 'pedestal' structures that elevate them above surrounding cell surfaces. Intimate adhesion and pedestal formation result from delivery of the EHEC type III secretion system (TTSS) effector proteins Tir and EspF(U) into the host cell and expression of the bacterial outer membrane adhesin, intimin. To investigate a role for DNA methylation during the regulation of adhesion and pedestal formation in EHEC, we deleted the dam (DNA adenine methyltransferase) gene from EHEC O157:H7 and demonstrate that this mutation results in increased interactions with cultured host cells. EHECDeltadam exhibits dramatically elevated levels of adherence and pedestal formation when compared with wild-type EHEC, and expresses significantly higher protein levels of intimin, Tir and EspF(U). Analyses of GFP fusions, Northern blotting, reverse transcription polymerase chain reaction, and microarray experiments indicate that the abundance of Tir in the dam mutant is not due to increased transcription levels, raising the possibility that Dam methylation can indirectly control protein expression by a post-transcriptional mechanism. In contrast to other dam-deficient pathogens, EHECDeltadam is capable of robust intestinal colonization of experimentally infected animals.
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Citation: Mol Microbiol. 2007 Mar;63(5):1468-81. Link to article on publisher's site