Analysis of the Roles of the cwlD Operon Products during Sporulation in Bacillus subtilis

• Main Author: Gilmore, Meghan Elizabeth
• Other Authors: Biology (Microbiology)
• Format: Others
• Language: en
• Published: Virginia Tech 2014
• Subjects: cortex; Bacillus subtilis; sporulation; peptidoglycan
• Online Access: http://hdl.handle.net/10919/35779; http://scholar.lib.vt.edu/theses/available/etd-11212000-132345/

CwlD has sequence similarities to N-acetyl muramoyl-L-alanine amidases, a class of enzymes known to cleave the bond between the peptide side chain and the N-acetyl muramic acid residue in cortex peptidoglycan formation during sporulation. A major difference between vegetative peptidoglycan and spore peptidoglycan is the presence of muramic-<FONT FACE="Symbol">d</FONT> -lactam (MAL) in spore peptidoglycan. It was previously determined that a <I>cwlD</I> null mutant does not contain muramic-<FONT FACE="Symbol">d</FONT> -lactam in the spore cortex peptidoglycan and the mutant spores were unable to complete germination. Therefore, it is believed that CwlD plays a role in MAL formation during sporulation. However, the specific role of the protein had not been demonstrated. It was also previously found that <I>cwlD</I> is in a two-gene operon with <I>orf1</I>. Orf1 is produced within the forespore with CwlD. The hypothesized role of Orf1 is to inhibit CwlD activity from within the forespore. Muramoyl-L-alanine amidase activity was demonstrated by CwlD <I>in vivo</I>. Therefore, CwlD is carrying out the first step of MAL synthesis, cleaving the peptide side chain while other enzymes are needed to complete MAL formation. Two different forms of CwlD were over-expressed, with and without the protein's signal peptide sequence. Both forms of the protein were purified and in both cases activity was undetectable. Antibodies specific for CwlD were obtained which can be used in future research as a tool to further characterize CwlD activity. A series of <I>B. subtilis</I> <I>cwlD</I> operon mutants were constructed altering the expression patterns of Orf1 and CwlD within the mother cell and forespore compartments. Various resistance properties and the germination ability of the mutant dormant spores were analyzed. It was determined that the absence of just Orf1 or Orf1 and CwlD from within the forespore has no effect on the phenotypes tested. Peptidoglycan from developing mutant forespores was extracted and analyzed throughout sporulation. Evidence was obtained demonstrating that the role of Orf1 is not to inhibit CwlD from within the forespore as hypothesized. === Master of Science