Open AccessExpression and Assembly of a Functional Type IV Secretion System Elicit Extracytoplasmic and Cytoplasmic Stress Responses in Escherichia coli
Author(s) -
Doris Zahrl,
Maria Wagner,
Karin Bischof,
Günther Koraimann
Publication year - 2006
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.00632-06
Subject(s) - biology , pilus , microbiology and biotechnology , pilin , mutant , escherichia coli , plasmid , gene , secretion , cytoplasm , regulation of gene expression , genetics , biochemistry
Conditions perturbing protein homeostasis are known to induce cellular stress responses in prokaryotes and eukaryotes. Here we show for the first time that expression and assembly of a functional type IV secretion (T4S) machinery elicit extracytoplasmic and cytoplasmic stress responses inEscherichia coli . After induction of T4S genes by a nutritional upshift and assembly of functional DNA transporters encoded by plasmid R1-16, host cells activated the CpxAR envelope stress signaling system, as revealed by induction or repression of downstream targets of the CpxR response regulator. Furthermore, we observed elevated transcript levels of cytoplasmic stress genes, such asgroESL , with a concomitant increase of σ32 protein levels in cells expressing T4S genes. AtraA null mutant of plasmid R1-16, which lacks the functional gene encoding the major pilus protein pilin, showed distinctly reduced stress responses. These results corroborated our conclusion that the activation of bacterial stress networks was dependent on the presence of functional T4S machinery. Additionally, we detected increased transcription from therpoHp 1 promoter in the presence of an active T4S system. Stimulation ofrpoHp 1 was dependent on the presence of CpxR, suggesting a hitherto undocumented link between CpxAR and σ32 -regulated stress networks.