Open AccessAutoactivation of the AggR regulator of enteroaggregative Escherichia coli in vitro and in vivo
Author(s) -
Morin Nicholas,
Tirling Chelsea,
Ivison Sabine M.,
Kaur Ajinder Pal,
Nataro James P.,
Steiner Theodore S.
Publication year - 2010
Publication title -
fems immunology & medical microbiology
Language(s) - English
Resource type - Journals
eISSN - 1574-695X
pISSN - 0928-8244
DOI - 10.1111/j.1574-695x.2009.00645.x
Subject(s) - enteroaggregative escherichia coli , biology , fimbria , dna footprinting , regulator , primer extension , virulence , microbiology and biotechnology , escherichia coli , plasmid , response regulator , transcriptional regulation , luciferase , promoter , genetics , gene , enterobacteriaceae , gene expression , nucleotide , transfection , mutant
Enteroaggregative Escherichia coli (EAEC) causes diarrhea in diverse populations worldwide. The AraC‐like regulator AggR is a key virulence regulator in EAEC. AggR‐regulated genes include those encoding the Aggregative Adherence Fimbria, the dispersin protein, and a type VI secretion system. This study characterizes the regulation of the aggR promoter (P aggR ). Using primer extension analysis, the transcriptional start site of the aggR promoter was located 40 nucleotides upstream of the translational start. P aggR was found to be autoregulated and DNA footprinting revealed the presence of two AggR‐binding sites: one upstream of the transcriptional start site and one downstream. Additionally, P aggR was found to be positively regulated by the DNA‐binding protein FIS and negatively regulated by the global regulator H‐NS. To further understand this complex regulation scheme, a bacterial luciferase reporter system was used with a mouse model of EAEC colonization. This allowed for the in vivo measurement of P aggR , P fis , and P hns activity. EAEC present in the mouse intestine possessed relatively high levels of P fis and P aggR activity and a low level of P hns when compared with in vitro experiments. The data provide significant insights into the regulation cascade leading to aggR expression in the mammalian intestine during EAEC infection.