The N-acetyltransferase RimJ responds to environmental stimuli to repress pap fimbrial transcription in Escherichia coli

Abstract

In uropathogenic Escherichia coli, P pili (Pap) facilitate binding to host epithelial cells and subsequent colonization. Whereas P pili can be produced at 37 degrees C, the expression of these fimbriae is suppressed at 23 degrees C. Previously, insertion mutations in rimJ, a gene encoding the N-terminal acetyltransferase of ribosomal protein S5, were shown to disrupt this thermoregulatory response, allowing papBA transcription at low temperature. In this study, we created an in-frame deletion of rimJ. This deletion relieved the repressive effects not only of low temperature but also of rich (Luria-Bertani [LB]) medium and glucose on papBA transcription, indicating that RimJ modulates papBA transcription in response to multiple environmental stimuli. papI transcription was also shown to be regulated by RimJ. papBA transcription is also controlled by a phase variation mechanism. We demonstrated that the regulators necessary to establish a phase ON state--PapI, PapB, Dam, Lrp, and cyclic AMP-CAP-are still required for papBA transcription in a rimJ mutant strain. rimJ mutations increase the rate at which bacteria transition into the phase ON state, indicating that RimJ inhibits the phase OFF-->ON transition. A DeltarimJ hns651 mutant is viable on LB medium but not on minimal medium. This synthetic lethality, along with transcriptional analyses, indicates that RimJ and H-NS work through separate pathways to control papBA transcription. Mutations in rimJ do not greatly influence the transcription of the fan, daa, or fim operon, suggesting that RimJ may be a pap-specific regulator. Overexpression of rimJ under conditions repressive for papBA transcription complements the DeltarimJ mutation but has little effect on transcription under activating conditions, indicating that the ability of RimJ to regulate transcription is environmentally controlled.

FIG. 1.

Effects of environmental stimuli on pap fimbrial transcription in wild-type and rimJ mutant strains. The bars indicate β-galactosidase activities measured in the wild-type strain DL1504 (solid bars), in strain CWZ388 containing the ΔrimJ mutation (open bars), and in strain DL1509 containing the rimJ-2::mTn10 mutation (hatched bars). β-Galactosidase activity was measured as described in Materials and Methods. Error is expressed as 1 standard deviation from the mean.

FIG. 2.

Effects of the ΔrimJ and hns651 mutations on papBA transcription. The bars indicate β-galactosidase activities measured in the wild-type (wt) strain DL1504, in the ΔrimJ mutant strain CWZ388, in the hns651 mutant strain DL1947, and in the ΔrimJ hns651 double-mutant strain CWZ403. β-Galactosidase activity was measured as described in Materials and Methods. Error is expressed as 1 standard deviation from the mean.

FIG. 3.

Effect of increasing levels of rimJ on papBA transcription. The strain CWZ395 containing pCWZ101 (rimJ under the control of the P_lac/ara-1 promoter) and pMV101 (lacI^q) was used in this experiment. IPTG was added at concentrations ranging from 0 to 1,000 μM as indicated to induce expression of rimJ. The data points indicate β-galactosidase activities measured after growth in M9 glyc at 37°C (circles), LB at 37°C (squares), and M9 glyc at 23°C (triangles). β-Galactosidase activity was measured as described in Materials and Methods. Error is expressed as ±1 standard deviation from the mean.