Roles of HdeA, HdeB, and HdeD chaperone proteins in the acid stress response of Klebsiella pneumoniae CG43

• Main Authors: Lin, Chen-Yi, 林珍儀
• Other Authors: Peng, Hwei-Lin
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/49432021325192842325

碩士 === 國立交通大學 === 生物科技系所 === 102 === Acid resistance or acid tolerance is an important adaptation for enterobacteria in order to evade the stomach acid before the intestinal tract colonization. Escherichia coli HdeA and HdeB, encoded on the acid fitness island (AFI) that is activated by acidic stress, function as chaperone in the periplasmic space to protect the proteins from damage. Analysis of the genome sequence of K. pneumoniae CG43 revealed two AFI homologs namely AFI-I and AFI-II. Interestingly, AFI-II is not found in the genome of NTUH-K2044 or MGH78578. The AFI-I contains hdeDB, hdeB1, yfdX and kvhAS, while AFI-II contains hdeA, hdeD1B2, kvgAS and kvgA1S1. The previous study of the specific gene deletion mutants revealed that the acid survival activity could be ranked as ΔhdeB1>ΔhdeD>ΔyfdX>ΔhdeB. Both the recombinant HdeB and YfdX exhibit chaperone activity, and the expression of the AFI-I gene is acid-inducible and positively regulated by RcsB under statically cultured condition. Here, the specific gene deletion mutants including ΔhdeA and ΔhdeB2 have been generated. The order of acid stress survivals is ΔhdeB1>ΔhdeD>ΔhdeB>ΔhdeB2, while ΔhdeA had no apparent change of the sensitivity when compared to the parental strain CG43S3. Nevertheless, the hdeA deletion exerts a profound reduction of the acid stress (pH2.5) survivals when the bacteria were grown to stationary phase. Increasing expression of hdeA could rescue the deletion defect of yfdX, hdeB, hdeDD1, or rcsB suggesting HdeA exhibits a strong chaperone activity. Moreover, phenylalanine 44 of HdeA was critical for the chaperone activity. Finally, the expression of hdeA and hdeB2D1 was not acid inducible and not affected by the deletion of rcsB or rpoS under shaking or static cultures.