Journal of Bacteriology, December 2005, p. 8055-8062, Vol. 187, No. 23
0021-9193/05/$08.00+0 doi:10.1128/JB.187.23.8055-8062.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Characterization of Bacillus anthracis Germinant Receptors In Vitro
Nathan Fisher and
Philip Hanna*
Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48104
Received 29 June 2005/
Accepted 12 September 2005
Bacillus anthracis begins its infectious cycle as a metabolically dormant cell type, the endospore. Upon entry into a host, endospores rapidly differentiate into vegetative bacilli through the process of germination, thus initiating anthrax. Elucidation of the signals that trigger germination and the receptors that recognize them is critical to understanding the pathogenesis of B. anthracis. Individual mutants deficient in each of the seven putative germinant receptor-encoding loci were constructed via temperature-dependent, plasmid insertion mutagenesis and used to correlate these receptors with known germinant molecules. These analyses showed that the GerK and GerL receptors are jointly required for the alanine germination pathway and also are individually required for recognition of either proline and methionine (GerK) or serine and valine (GerL) as cogerminants in combination with inosine. The germinant specificity of GerS was refined from a previous study in a nonisogenic background since it was required only for germination in response to aromatic amino acid cogerminants. The gerA and gerY loci were found to be dispensable for recognition of all known germinant molecules. In addition, we show that the promoter of each putative germinant receptor operon, except that of the gerA locus, is active during sporulation. A current model of B. anthracis endospore germination is presented.
* Corresponding author. Mailing address: Department of Microbiology and Immunology, University of Michigan Medical School, 5641 Medical Science Building II, Box 0620, Ann Arbor, MI 48104. Phone: (734) 615-3706. Fax: (734) 764-3562. E-mail: pchanna{at}umich.edu.
Journal of Bacteriology, December 2005, p. 8055-8062, Vol. 187, No. 23
0021-9193/05/$08.00+0 doi:10.1128/JB.187.23.8055-8062.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
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Copyright © 2005 by the American Society for Microbiology. All rights reserved.