CRP-Cyclic AMP regulates the expression of type 3 fimbriae via cyclic di-GMP in klebsiella pneumonia

Ching Ting Lin, Tien Huang Lin, Chien Chen Wu, Lei Wan, Chun Fa Huang, Hwei-Ling Peng

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Klebsiella pneumoniae is the predominant pathogen isolated from liver abscesses of diabetic patients in Asian countries. However, the effects of elevated blood glucose levels on the virulence of this pathogen remain largely unknown. Type 3 fimbriae, encoded by the mrkABCDF genes, are important virulence factors in K. pneumoniae pathogenesis. In this study, the effects of exogenous glucose and the intracellular cyclic AMP (cAMP) signaling pathway on type 3 fimbriae expression regulation were investigated. The production of MrkA, the major subunit of type 3 fimbriae, was increased in glucose-rich medium, whereas cAMP supplementation reversed the effect. MrkA production was markedly increased by cyaA or crp deletion, but slightly decreased by cpdA deletion. In addition, the mRNA levels of mrkABCDF genes and the activity of P mrkA were increased in Δcrp strain, as well as the mRNA levels of mrkHIJ genes that encode cyclic di-GMP (c-di-GMP)-related regulatory proteins that influence type 3 fimbriae expression. Moreover, the activities of P mrkHI and P mrkJ were decreased in ΔlacZΔcrp strain. These results indicate that CRP-cAMP down-regulates mrkABCDF and m mrkHIJ at the transcriptional level. Further deletion of mrkH or mrkI in Δcrp strain diminished the production of MrkA, indicating that MrkH and MrkI are required for the CRP regulation of type 3 fimbriae expression. Furthermore, the high activity of PmrkHI in the ΔlacZΔcrp strain was diminished in ΔlacZΔcrpΔmrkHI, but increased in the ΔlacZΔcrpΔmrkJ strain. Deletion of crp increased the intracellular c-di-GMP concentration and reduced the phosphodiesterase activity. Moreover, we found that the mRNA levels of multiple genes related to c-di-GMP metabolism were altered in Δcrp strain. These indicatethat CRP regulates type 3 fimbriae expression indirectly via the c-di-GMP signaling pathway. In conclusion, we found evidence of a coordinated regulation of type 3 fimbriae expression by the CRP-cAMP and c-di-GMP signaling pathways in K. pneumoniae.

Original languageEnglish
Article numbere0162884
JournalPLoS ONE
Issue number9
StatePublished - 1 Sep 2016


Dive into the research topics of 'CRP-Cyclic AMP regulates the expression of type 3 fimbriae via cyclic di-GMP in klebsiella pneumonia'. Together they form a unique fingerprint.

Cite this