title: Type 3 fimbriae and biofilm formation are regulated by the transcriptional regulators MrkHI in Klebsiella pneumoniae.
abstract: Klebsiella pneumoniae is an opportunistic pathogen which frequently causes hospital-acquired urinary and respiratory tract infections. K. pneumoniae may establish these infections in vivo following adherence, using the type 3 fimbriae, to indwelling devices coated with extracellular matrix components. Using a colony immunoblot screen, we identified transposon insertion mutants which were deficient for type 3 fimbrial surface production. One of these mutants possessed a transposon insertion within a gene, designated mrkI, encoding a putative transcriptional regulator. A site-directed mutant of this gene was constructed and shown to be deficient for fimbrial surface expression under aerobic conditions. MrkI mutants have a significantly decreased ability to form biofilms on both abiotic and extracellular matrix-coated surfaces. This gene was found to be cotranscribed with a gene predicted to encode a PilZ domain-containing protein, designated MrkH. This protein was found to bind cyclic-di-GMP (c-di-GMP) and regulate type 3 fimbrial expression.
authors.affiliation: Department of Microbiology, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: Jeremiah G
authors.initials: JG
authors.lastname: Johnson
authors.forename: Caitlin N
authors.initials: CN
authors.lastname: Murphy
authors.forename: Jean
authors.initials: J
authors.lastname: Sippy
authors.forename: Tylor J
authors.initials: TJ
authors.lastname: Johnson
authors.forename: Steven
authors.initials: S
authors.lastname: Clegg
mesh_terms: D000595:Amino Acid Sequence; D018441:Biofilms; D036781:Fimbriae Proteins / Q000235:genetics / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D007711:Klebsiella pneumoniae / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D014158:Transcription, Genetic
chemical_list: D036781:Fimbriae Proteins