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Logo of bmcmicrBioMed Centralsearchsubmit a manuscriptregisterthis articleBMC Microbiology
 
BMC Microbiol. 2012; 12: 148.
Published online Jul 24, 2012. doi:  10.1186/1471-2180-12-148
PMCID: PMC3423075
Role of the small RNA RyhB in the Fur regulon in mediating the capsular polysaccharide biosynthesis and iron acquisition systems in Klebsiella pneumoniae
Su-Hua Huang,#1 Chien-Kuo Wang,#1 Hwei-Ling Peng,2 Chien-Chen Wu,2 Ying-Tsong Chen,3,4,5 Yi-Ming Hong,6 and Ching-Ting Lincorresponding author6
1Department of Biotechnology, Asia University, Taichung 41354, Taiwan
2Department of Biological Science and Technology, National Chiao Tung University, Hsin Chu 30068, Taiwan
3Institute of Genomics and Bioinformatics, National Chung Hsing University, Tai Chung City 40227, Taiwan
4Biotechnology Center, National Chung Hsing University, Tai Chung City 40227, Taiwan
5Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli County 35053, Taiwan
6School of Chinese Medicine, China Medical University, Taichung 40402, Taiwan
corresponding authorCorresponding author.
#Contributed equally.
Su-Hua Huang: shhuang/at/asia.edu.tw; Chien-Kuo Wang: ck/at/asia.edu.tw; Hwei-Ling Peng: hlpeng/at/cc.nctu.edu.tw; Chien-Chen Wu: allen8828015/at/hotmail.com; Ying-Tsong Chen: onion/at/nhri.org.tw; Yi-Ming Hong: sharon780405/at/hotmail.com; Ching-Ting Lin: gingting/at/mail.cmu.edu.tw
Received May 15, 2012; Accepted July 9, 2012.
Abstract
Background
The capsular polysaccharide (CPS) and iron acquisition systems are important determinants of Klebsiella pneumoniae infections, and we have previously reported that the ferric uptake repressor (Fur) can play dual role in iron acquisition and CPS biosynthesis. In many bacteria, Fur negatively controls the transcription of the small non-coding RNA RyhB to modulate cellular functions and virulence. However, in K. pneumoniae, the role played by RyhB in the Fur regulon has not been characterised. This study investigated Fur regulation of ryhB transcription and the functional role of RyhB in K. pneumoniae.
Results
Deletion of fur from K. pneumoniae increased the transcription of ryhB; the electric mobility shift assay and the Fur-titration assay revealed that Fur could bind to the promoter region of ryhB, suggesting that Fur directly represses ryhB transcription. Additionally, in a Δfur strain with elevated CPS production, deletion of ryhB obviously reduced CPS production. The following promoter-reporter assay and quantitative real-time PCR of cps genes verified that RyhB activated orf1 and orf16 transcription to elevate CPS production. However, deletion of ryhB did not affect the mRNA levels of rcsA, rmpA, or rmpA2. These results imply that Fur represses the transcription of ryhB to mediate the biosynthesis of CPS, which is independent of RcsA, RmpA, and RmpA2. In addition, the Δfur strain’s high level of serum resistance was attenuated by the deletion of ryhB, indicating that RyhB plays a positive role in protecting the bacterium from serum killing. Finally, deletion of ryhB in Δfur reduced the expression of several genes corresponding to 3 iron acquisition systems in K. pneumoniae, and resulted in reduced siderophore production.
Conclusions
The regulation and functional role of RyhB in K. pneumoniae is characterized in this study. RyhB participates in Fur regulon to modulate the bacterial CPS biosynthesis and iron acquisition systems in K. pneumoniae.
Keywords: RyhB, Fur, Capsular polysaccharide, Iron acquisition system, Klebsiella pneumoniae
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