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A plasmid‐encoded regulator couples the synthesis of toxins and surface structures in Bacillus anthracis
Author(s) -
Mignot Tâm,
Mock Michèle,
Fouet Agnès
Publication year - 2003
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2003.03345.x
Subject(s) - bacillus anthracis , biology , plasmid , gene , anthrax toxin , genetics , activator (genetics) , regulator gene , regulator , transcription (linguistics) , virulence , promoter , transcription factor , regulation of gene expression , recombinant dna , gene expression , bacteria , fusion protein , linguistics , philosophy
Summary Transcription of the major Bacillus anthracis virulence genes is triggered by CO 2 , a signal believed to reflect the host environment. A 180 kb plasmid, pXO1, carries the anthrax toxin genes and the genes responsible for their regulation, pagR and atxA ; the latter encodes a major trans ‐activator. It has long been known that pXO1 genes have major effects on the physiology of B. anthracis , probably through regulatory cross‐talk between plasmid and chromosomal genes. Accordingly, we found that the chromosomal S‐layer genes, sap and eag , are regulated by pXO1 genes so that only eag is significantly expressed in the presence of CO 2 . This effect results from the product of pagR acting as the most downstream element of a signalling cascade initiated by AtxA. In vitro evidence showed that PagR is a transcription factor that controls the S‐layer genes by direct binding on their promoter regions. This work provides evidence that AtxA is a master regulator that co‐ordinates the response to host signals by orchestrating positive and negative controls over genes located on all genetic elements.