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The frequency of expression of pyelonephritis-associated pili is under regulatory control
D Low1, E N Robinson, Z A McGee
1Department of Pathology, University of Utah School of Medicine, Salt Lake City 84132.
Insights
Escherichia coli strains C1212 and K-12 show differential regulation of pyelonephritis-associated pili (pap) DNA sequences. Pap-21 presence in trans activates pap-17 expression in E. coli K-12.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Escherichia coli urinary tract infections are often associated with pyelonephritis-associated pili (pap).
- Strain C1212 possesses two distinct pap DNA sequences, pap-17 and pap-21, encoding unique pilin monomers.
Purpose of the Study:
- To investigate the differential expression and regulation of pap-17 and pap-21 in Escherichia coli.
- To determine the genetic elements responsible for regulating pilin-17 expression.
Main Methods:
- Analysis of pilin expression in E. coli strain C1212 and E. coli K-12.
- Manipulation of pap DNA sequences in single-copy and multicopy vectors.
- Subcloning of pap-21 to identify regulatory regions.
Main Results:
- Strain C1212 predominantly expresses pilin-21, with low-level expression of pilin-17.
- Multicopy pap-17 in E. coli K-12 leads to high pilin-17 expression, losing strain C1212's regulation.
- A 2.2 kb sequence adjacent to the pap-21 gene activates pilin-17 expression in trans.
Conclusions:
- Pap-17 expression is tightly regulated in its native context within strain C1212.
- Pap-21, or a specific region within it, acts in trans to activate pap-17 expression in E. coli K-12.
- The copy number of pap DNA significantly impacts pilin expression regulation.
Abstract:
The Escherichia coli urinary tract isolate C1212 contains two pyelonephritis-associated pili (pap) DNA sequences designated here as pap-17 and pap-21. Each of these pap sequences encodes antigenically-distinct pilin monomers, pilin-17 and pilin-21, respectively. Most individual strain C1212 cells isolated from a single bacterial colony expressed pilin-21. Only a small fraction (5%) of strain C1212 cells expressed pilin-17. Most of the latter population simultaneously expressed pilin-21, but a low percentage of cells expressed pili composed of pilin-17 alone. In contrast, almost every E. coli K-12 cell containing multicopy pap-17 expressed pilin-17 at the cell surface. These results indicated that the regulation of pilin-17 expression observed for strain C1212 was lost when pap-17 was in the multicopy state. Transfer of pap-17 to a single copy vector resulted in a pilin-17 expression frequency lower than strain C1212 (1%). Using E. coli K-12 containing single copy pap-17, we found that the frequency of pilin-17 expression increased about 15-fold when pap-21 was present in multiple copies in trans. Subcloning of pap-21 showed that a 2.2 kilobase-pair DNA sequence adjacent to, but not including, the pilin-21 structural gene was sufficient for activation of pilin-17 expression.