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 ␦-lactam. Production of muramic ␦-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 ␦-lactam formation. Expression of CwlD in Escherichia coli results in muramoyl L-Alanine amidase activity but no muramic ␦-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 ␦-lactam. CwlD and PdaA are necessary and sufficient for muramic ␦-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.Bacterial endospores can maintain a dormant, highly resistant state for long periods and then, under favorable conditions, rapidly germinate to produce vegetative cells. Spore dormancy and heat resistance are dependent on the relative dehydration of the spore core (6, 24, 28). Spore core dehydration requires the integrity of a thick spore peptidoglycan wall, and peptidoglycan hydrolysis is required for rehydration and resumption of spore core metabolism during spore germination (27,31).The spore peptidoglycan is composed of two contiguous layers that are synthesized between the two membranes surrounding the developing forespore. The inner layer, the germ cell wall, makes up only 10 to 15% of the total spore peptidoglycan (23) and is apparently synthesized by proteins expressed on the surface of the inner forespore membrane (22, 35). The germ cell wall has a structure resembling the peptidoglycan of the vegetative cell wall (23), is maintained during spore germination to serve as the initial wall of the outgrowing spore (5), and appears to function as a template for proper synthesis of the outer spore peptidoglycan layers, the cortex (22). The cortex makes up Ͼ80% of the spore peptidoglycan (23), is synthesized by proteins present on the surface of the outer forespore membrane (10, 35), is rapidly degraded...

Background. Gastrointestinal stromal tumor (GIST) is an uncommon tumor of the GI tract usually seen in elderly patients, often difficult to diagnose because of the unspecific symptoms such as abdominal pain and fullness. Recurrent GIST may have an even more obscure clinical presentation. Case Report. A 44-year-old female with a history of surgically treated GIST presented to the emergency room complaining of acute onset sharp RLQ pain, nausea, and vomiting. Clinically, she had RLQ tenderness with rebound, her WBC was elevated, and CT scan showed signs of appendicitis and also soft tissue masses suspicious for malignancy. After contemplating treatment options including antibiotics and further workup, it was recommended to proceed with surgery. Laparoscopy showed a thickened appendix with nodular infiltration and multiple mass-like lesions in the RLQ not amendable to minimal invasive resection. From a lower midline incision, an open appendectomy and excision of multiple masses in the terminal ileum and in the abdominal wall were done. Narrow-based Meckel’s diverticulum with multiple nodular lesions was also removed. Pathology identified appendicitis and serosal involvement of GIST in all specimens staining positive for CD68, CD117, and vimentin. The patient was started on imatinib and remained recurrence-free after 6 months. Conclusions. This case illustrates a rare presentation of acute symptomatic recurrent metastatic GIST. Our patient was unusually young, and GIST recurrence presented with acute RLQ pain suggestive for acute appendicitis and also involved Meckel’s diverticulum. Surgical debulking followed by imatinib seems to be a reasonable approach in such cases.

Background. Lumbar hernias are rare abdominal hernias. Surgery is the only treatment option but remains challenging. Posterior incisional hernias are even rarer especially with incarceration of intra-abdominal contents. Case Presentation. A 68-year old female presented with a 3-day history of worsening acute abdominal pain and distension, with multiple episodes of emesis. A CT scan indicated a large incarcerated posterolateral abdominal hernia. The patient had a history of resection of a sarcoma on her back as a child and also received chemotherapy and radiation. During emergency laparoscopy, a hemorrhagic small bowel segment incarcerated in the hernia was reduced and resected, and the distended small bowel was decompressed. An elective hernia repair was scheduled. After temporary clinical improvement, the patient again developed abdominal pain, distention, and emesis. During emergency laparotomy, a large hematoma in the right flank was found and partially evacuated. The right colon was mobilized out of the hernia and the duodenum was kocherized. A 20×20 cm BIO-A mesh was placed on top of the Gerota fascia and cranially tucked under liver segment VI. Anteriorly, the mesh was fixated with absorbable tacks. The duodenum and colon were placed into the mesh pocket. A postoperative CT scan identified a 2 cm pseudoaneurysm of a side branch of a lumbar artery, and the bleeding source was embolized. The postoperative course was complicated by Clostridium difficile-associated colitis, but ultimately, the patient recovered fully. At 6-month follow-up, there was no evidence for a recurrent hernia. Discussion. There is a paucity of literature concerning lumbar incisional hernias. Repair with bioabsorbable mesh seems feasible, but longer follow-up is necessary as the mesh was placed in an unusual fashion due to the retroperitoneal hematoma. The exact cause of the hemorrhage is unclear and may have been caused during the initial incarceration, during surgery, or may be a late complication of her previous radiation.