ISSN:
1365-2958
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Biologie
,
Medizin
Notizen:
Lipopolysaccharide (LPS) is a glycolipid present in the outer membrane of all Gram-negative bacteria, and it is one of the signature molecules recognized by the receptors of the innate immune system. In addition to its lipid A portion (the endotoxin), its O-chain polysaccharide (the O-antigen) plays a critical role in the bacterium–host interplay and, in a number of bacterial pathogens, it is a virulence factor. We present evidence that, in Yersinia enterocolitica serotype O:8, a complex signalling network regulates O-antigen expression in response to temperature. Northern blotting and reporter fusion analyses indicated that temperature regulates the O-antigen expression at the transcriptional level. Promoter cloning showed that the O-antigen gene cluster contains two transcriptional units under the control of promoters Pwb1 and Pwb2. The activity of both promoters is under temperature regulation and is repressed in bacteria grown at 37°C. We demonstrate that the RosA/RosB efflux pump/potassium antiporter system and Wzz, the O-antigen chain length determinant, are indirectly involved in the regulation mainly affecting the activity of promoter Pwb2. The rosAB transcription, under the control of Pros, is activated at 37°C, and Pwb2 is repressed through the signals generated by the RosAB system activation, i.e. decreased [K+] and increased [H+]. The wzz transcription is under the control of Pwb2, and we show that, at 37°C, overexpression of Wzz downregulates slightly the Pwb1 and Pwb2 activities and more strongly the Pros activity, with the net result that more O-antigen is produced. Finally, we demonstrate that overexpression of Wzz causes membrane stress that activates the CpxAR two-component signal transduction system.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1046/j.1365-2958.2002.02940.x
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