This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Supplemental material
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Google Scholar
Right arrow Articles by Shimizu, T.
Right arrow Articles by Noda, M.
PubMed
Right arrow PubMed Citation
Right arrow Articles by Shimizu, T.
Right arrow Articles by Noda, M.

 Previous Article  |  Next Article 

Infection and Immunity, July 2009, p. 2813-2823, Vol. 77, No. 7
0019-9567/09/$08.00+0     doi:10.1128/IAI.00060-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Shiga Toxin 2 Is Specifically Released from Bacterial Cells by Two Different Mechanisms{triangledown} ,{dagger}

Takeshi Shimizu,* Yuko Ohta, and Masatoshi Noda

Department of Molecular Infectiology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chiba, Japan 260-8670

Received 16 January 2009/ Returned for modification 20 February 2009/ Accepted 10 April 2009

Shiga toxin 1 (Stx1) is located in the periplasmic fraction, while Stx2 is found in the extracellular fraction, suggesting that enterohemorrhagic Escherichia coli (EHEC) contains a specific Stx2 release system. Both stx1 and stx2 are found within the late operons of Stx-encoding phages. Stx2 production is greatly induced by mitomycin C, suggesting that stx2 can transcribe from the late phage promoter of the Stx2-encoding phage. However, the Stx1 promoter adjacent to stx1 is a dominant regulatory element in Stx1 production. With the deletion of phage lysis genes of the Stx2-encoding phage, Stx2 remains in the bacterial cells. Further, we demonstrate that the Stx2-encoding phage, but not the Stx1-encoding phage, is spontaneously induced at extremely low rates. These results indicate that spontaneously specific Stx2-encoding phage induction is involved in specific Stx2 release from bacterial cells. Furthermore, to examine whether another system for specific Stx2 release is present in EHEC, we analyze the stx-replaced mutants. As expected, Stx2 derived from the Stx1 promoter is located in both the extracellular and cell-associated fractions, while mutant Stx2 (B subunit, S31N) derived from the Stx1 promoter is found only in the cell-associated fraction. These results indicate that EHEC has another Stx2 release system that strictly recognizes the serine 31 residue of the B subunit. Overall, we present evidence that specific Stx2 release from bacterial cells is involved in both the Stx2-encoding phage induction system and another Stx2 release system.

* Corresponding author. Mailing address: Department of Molecular Infectiology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chiba, 260-8670, Japan. Phone: 81-43-226-2048. Fax: 81-43-226-2049. E-mail: tshimizu{at}faculty.chiba-u.jp

{triangledown} Published ahead of print on 20 April 2009.

{dagger} Supplemental material for this article may be found at http://iai.asm.org/.

Editor: B. A. McCormick

Infection and Immunity, July 2009, p. 2813-2823, Vol. 77, No. 7
0019-9567/09/$08.00+0     doi:10.1128/IAI.00060-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»