Differential effects and interactions of endogenous and horizontally acquired H-NS-like proteins in pathogenic Escherichia coli
© 2009 The Authors. Journal compilation © 2009 Blackwell Publishing Ltd
The nucleoid-associated protein H-NS is important for gene regulation in Escherichia coli. We have studied H-NS interaction with StpA and an uncharacterized H-NS-like protein, Hfp, in the uropathogenic E. coli isolate 536 that expresses all three nucleoid-associated proteins. We found distinct interactions of the three proteins at the protein level, resulting in the formation of heteromers, as well as differences in their gene expression at the transcriptional level. Mutants lacking either StpA or Hfp alone did not exhibit a phenotype at 37 degrees C, which is consistent with a low level of expression at that temperature. Expression of the hfp and stpA genes was found to be induced by apparently diametrical conditions, and StpA and Hfp levels could be correlated to modulatory effects on the expression of different H-NS targets, the bgl operon and operons for virulence factors such as fimbriae and capsular polysaccharide. The hns/hfp and hns/stpA double mutants displayed severe growth defects at low and high temperatures respectively. Our findings demonstrated different requirements for the alternative H-NS/Hfp/StpA combinations under these growth conditions. We propose that Hfp and StpA have distinct functions and roles in a dynamic pool of nucleoid-associated proteins that is adapting to requirements in a particular environment.
The Würzburg group was supported by the Deutsche Forschungsgemeinschaft (SFB479, TP A1). The work in Umeå was supported by grants from the Swedish Research Council, the Swedish Foundation for International Cooperation in Research and Higher Education (STINT), the Faculty of Medicine at Umeå University, and it was performed within the Umeå Centre for Microbial Research (UCMR). G.S. and L.E. were supported by the Hungarian Research Foundation (OTKA 62092). This work was carried out in the frame of the European Virtual Institute for Functional Genomics of Bacterial Pathogens (CEE LSHB-CT-2005-512061) and the ERA-NET project ‘Deciphering the intersection of commensal and extraintestinal pathogenic E. coli’.
This is the final version of the article. Available from Wiley via the DOI in this record
Vol. 75 (2), pp. 280 - 293
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