Journal
MICROBIOLOGY-SGM
Volume 158, Issue -, Pages 1045-1056Publisher
SOC GENERAL MICROBIOLOGY
DOI: 10.1099/mic.0.053801-0
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Funding
- National Science Council (NSC) [97-2320-B-009-001-MY3, NRPGM-98IDI005, NSC99-2120 M-007-001]
- National Chiao Tung University
- Ministry of Education, Taiwan, ROC [100W962]
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Type 3 fimbriae play a crucial role in Klebsiella pneumoniae biofilm formation, but the mechanism of the regulation of the type 3 fimbrial operon is largely unknown. In K. pneumoniae CG43, three regulatory genes, mrkH, mrkI and mrkJ, are located downstream of the type 3 fimbrial genes mrkABCDF. The production of the major pilin MrkA is abolished by the deletion of mrkH or mrkI but slightly increased by the deletion of mrkJ. Additionally, quantitative RT-PCR and a promoter reporter assay of mrkHI verified that the transcription of mrkHI was activated by MrkI, suggesting autoactivation of mrkHI transcription. In addition, sequence analysis of the mrkH promoter region revealed a putative ferric uptake regulator (Fur) box. Deletion of fur decreased the transcription of mrkH, mrkI and mrkA. The expression of type 3 fimbriae and bacterial biofilm formation were also reduced by the deletion of fur. Moreover, a recombinant Fur was found to be able to bind both promoters, with higher affinity for P-mrkH than P-mrkA, implying that Fur controls type 3 fimbriae expression via MrkHI. We also proved that iron availability can influence type 3 fimbriae activity.
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