Study on the fimbrial expression in Klebsiella pneumoniae
| Autor: | Zhao-Yang Liao, 廖朝陽 |
|---|---|
| Rok vydání: | 2007 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 95 There are nine fimbiral operons identified in the genome of Klebsiella pneumoniae NTUH-K2044, a highly invasive strain isolated from Taiwan university hospital, by the HMMER search. The fim and mrk fimbriae had been described previously, but the others are novel fimbrial operons and are respectively named kpa, kpb, kpc, kpd, kpe, kpf, and kpg. The putative promoters of the nine operons were isolated, cloned in a LacZ reporter plasmid and the activities measured. In K. pneumoniae CG43S3Z01, the promoters of type 1 fimbriae (PfimA and PfimB) and type 3 fimbriae (PmrkA) had higher level of activity than those of the other fimbrial promoters. The activity of PfimA, PfimB, and PmrkA were enhanced under static cultures and the cultures addition with glucose or glycerol. On the other hand, the expression of fimB and mrkA were suppressed while the bacteria subject to higher osmotic pressure (＞200 mM NaCl), oxidative stress (60 �嵱 H2O2), or the pH switch from 5.5 to 8. Interestingly, the overexpression of KpdR, a putative response regulator located upstream of the kpd gene cluster, appeared to decrease the biofilm formation and increase expression of beta-lactamase TEM-116 in both K. pneumoniae NTUH-K 2044 and CG43S3Z01. This implied a regulatory role of KpdR in the biofilm formation and also the resistance to the beta-lactam drug. Searching for the gene of blaTEM-116 and construction of the kpdR and blaSHV-1a mutants are in process. In the meantime, over-expressions of two other putative regulators, KpbR and KpfR, in K. pneumoniae appeared to interfere growth of the bacteria. Finally, the deletion of phgS or phgM was found to reduce not only the expression of type 3 fimbriae but also the activity of PkpgA. Truncation of the predicted consensus sequences for PhgS binding from PkpgA or PmrkA abolished the PhgS dependent expression. It was suggested that a regulatory role of PhgS for the expression of the two fimbriae. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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