RESUMO
By evolving strains of E. coli that hyper-resist sedimentation, we discovered an uncharacterized mechanism that bacteria can use to remain in suspension indefinitely without expending energy. This unusual phenotype was traced to the anchoring of long colanic acid polymers (CAP) that project from the cell surface. Although each characterized mutant activated this same mechanism, the genes responsible and the strengths of the phenotypes varied. Mutations in rcsC, lpp, igaA, or the yjbEFGH operon were sufficient to stimulate sedimentation resistance, while mutations altering the cps promoter, cdgI, or yjbF provided phenotypic enhancements. The sedimentation resistances changed in response to temperature, growth phase, and carbon source and each mutant exhibited significantly reduced biofilm formation. We discovered that the degree of colony mucoidy exhibited by these mutants was not related to the degree of Rcs pathways activation or to the amount of CAP that was produced; rather, it was related to the fraction of CAP that was shed as a true exopolysaccharide. Therefore, these and other mutations that activate this phenotype are likely to be absent from genetic screens that relied on centrifugation to harvest bacteria. We also found that this anchored CAP form is not linked to LPS cores and may not be attached to the outer membrane.IMPORTANCEBacteria can partition in aqueous environments between surface-dwelling, planktonic, sedimentary, and biofilm forms. Residence in each location provides an advantage depending on nutritional and environmental stresses and a community of a single species is often observed to be distributed throughout two or more of these niches. Another adaptive strategy is to produce an extracellular capsule, which provides an environmental shield for the microbe and can allow escape from predators and immune systems. We discovered that bacteria can either shed or stably anchor capsules to dramatically alter their propensity to sediment. The degree to which the bacteria anchor their capsule is controlled by a stress sensing system, suggesting that anchoring may be used as an adaptive response to severe environmental challenges.
RESUMO
Small bowel cancer is a rare cause of small bowel obstruction (SBO) that is often discovered too late, leading to a poor prognosis at diagnosis. This case describes an African American patient with a previous history of abdominal surgery who presented to the emergency department with a partial small bowel obstruction (PSBO) that failed to resolve with conservative measures, therefore requiring surgical intervention. An exploratory laparoscopy revealed a firm apple core mass obstructing the lumen of the proximal jejunum 20 cm from the ligament of Treitz. The involved portion of the small bowel was resected with wide margins and sent to pathology. The small bowel was reconstructed by a functional end-to-end anastomosis, and the patient was admitted for observation until the return of bowel function. The pathology report, returned four weeks after the patient's discharge, reported metastatic adenocarcinoma originating from the small intestine. The patient was referred to oncology for further management of his metastatic cancer. Small bowel cancer, although rare, should always be part of the differential diagnosis in the case of small bowel obstruction. If cancer is suspected during exploratory surgery, the entire peritoneal cavity should be explored, and oncologic bowel resection should be performed with adequate margins. Final staging then occurs in the postoperative period.