Regulatory interplay between pap operons in uropathogenic Escherichia coli.
Pathogenic bacteria have a large repertoire of surface organelles involved in adherence, motility and protein export, but how individual bacteria co-ordinate surface organelle expression to prevent interference and excessive immune stimulation is unclear. Phase variation is a mechanism by which expression of surface factors is limited to a fraction of the bacterial population; however, the presence of multiple homologous surface structures controlled by related mechanisms and regulators antagonizes the independent expression achieved by phase variation. To investigate whether other mechanisms have evolved to sort out the bacterial cell surface, we examined regulatory cross-talk between multiple phase-variable pyelonephritis-associated pili (pap) operons in Escherichia coli isolates associated with urinary tract infections. Allelic variation identified in the regulatory regions and regulators acts synergistically to limit coexpression of homologous fimbrial operons. In particular, there is evidence that papI is under positive selection and PapI variants displayed differences in their capacity to activate related pap operons. Alleles of the high-affinity binding site for PapB were shown to contain a variable number of (T/A)(3) repeats occurring every 9 bp that altered the sensitivity of pap operon activation. Taken together with other examples of surface organelle cross-talk, we illustrate how this regulation could promote sequential expression.
Totsika
Makrina
M
Centre for Infectious Diseases, Chancellor's Building, University of Edinburgh, Edinburgh EH16 4SB, UK.
Beatson
Scott A
SA
Holden
Nicola
N
Gally
David L
DL
D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics* / Q000502:physiology; D004927:Escherichia coli Infections / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000502:physiology; D036781:Fimbriae Proteins / Q000235:genetics / Q000502:physiology; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000502:physiology; D016368:Frameshift Mutation; D015964:Gene Expression Regulation, Bacterial; D014644:Genetic Variation; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology; D008954:Models, Biological; D009876:Operon; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000235:genetics* / Q000502:physiology; D016415:Sequence Alignment; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology; D014552:Urinary Tract Infections / Q000235:genetics / Q000382:microbiology*
D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C086707:PapI protein, E coli; D012097:Repressor Proteins; D014157:Transcription Factors; C116245:atpD protein, E coli; D036781:Fimbriae Proteins