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Journal of Bacteriology, January 2004, p. 80-89, Vol. 186, No. 1
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.1.80-89.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Production of Muramic {delta}-Lactam in Bacillus subtilis Spore Peptidoglycan

Meghan E. Gilmore,{dagger} Dabanjan Bandyopadhyay, Amanda M. Dean,{ddagger} Sarah D. Linnstaedt,§ and David L. Popham*

Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061

Received 26 August 2003/ Accepted 8 October 2003

Bacterial spore heat resistance is primarily dependent upon dehydration of the spore cytoplasm, a state that is maintained by the spore peptidoglycan wall, the spore cortex. A peptidoglycan structural modification found uniquely in spores is the formation of muramic {delta}-lactam. Production of muramic {delta}-lactam in Bacillus subtilis requires removal of a peptide side chain from the N-acetylmuramic acid residue by a cwlD-encoded muramoyl-L-Alanine amidase. Expression of cwlD takes place in both the mother cell and forespore compartments of sporulating cells, though expression is expected to be required only in the mother cell, from which cortex synthesis derives. Expression of cwlD in the forespore is in a bicistronic message with the upstream gene ybaK. We show that ybaK plays no apparent role in spore peptidoglycan synthesis and that expression of cwlD in the forespore plays no significant role in spore peptidoglycan formation. Peptide cleavage by CwlD is apparently followed by deacetylation of muramic acid and lactam ring formation. The product of pdaA (yfjS), which encodes a putative deacetylase, has recently been shown to also be required for muramic {delta}-lactam formation. Expression of CwlD in Escherichia coli results in muramoyl L-Alanine amidase activity but no muramic {delta}-lactam formation. Expression of PdaA alone in E. coli had no effect on E. coli peptidoglycan structure, whereas expression of CwlD and PdaA together resulted in the formation of muramic {delta}-lactam. CwlD and PdaA are necessary and sufficient for muramic {delta}-lactam production, and no other B. subtilis gene product is required. PdaA probably carries out both deacetylation and lactam ring formation and requires the product of CwlD activity as a substrate.


* Corresponding author. Mailing address: Department of Biology, Virginia Tech, 2119 Derring Hall MC0406, Blacksburg, VA 24061. Phone: (540) 231-2529. Fax: (540) 231-9307. E-mail: dpopham{at}vt.edu.

{dagger} Present address: Channing Laboratory and Division of Infectious Diseases, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115.

{ddagger} Present address: Naval Surface Warfare Center, Dahlgren Division 17320, Dahlgren, VA 22448-5100.

§ Present address: Office of Microbiology & Immunology, Georgetown University Medical Center, Washington, DC 20007.


Journal of Bacteriology, January 2004, p. 80-89, Vol. 186, No. 1
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.1.80-89.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.




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