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The partitioning of PCBs to natural populations of aquatic heterotrophic bacteria from Lake Superior was measured in both field and laboratory studies to better understand the role of bacteria and the microbial food web in persistent, bioaccumulative, toxic organic contaminant (PBT) transfer. A filtration method that separated material >1 microm from that <1 microm was used to collect and measure PCB concentrations in the bacterial fraction. We used bacterial biovolume and a conversion factor to calculate bacterial carbon, which was used to normalize PCB concentrations. The range of total PCB concentrations in the bacterial fraction (61-337 ng/g organic carbon; OC) was similar, but generally higher than that of the total particulate fraction (36-324 ng/g OC). Measured log bioaccumulation factors (BAFoc, bacterial fraction; Koc, total particulate) were significantly greater in the bacterial fraction than in the total particulate fraction (bacterial range 6.7-7.3, total particulate range 5.8-7.0). Laboratory experiments demonstrated that a hexachlorobiphenyl reached steady state with a natural community of Lake Superior bacteria within 48 h and had a mean log BAFoc of 7.5 +/- 1.9. The octanol/ water partition coefficient (Kow) consistently under-predicted BAFoc, however, the magnitude of the under-prediction was still within the range of uncertainty in food web modeling (factors of 3-9). Food web modeling and risk assessment of PBT bioaccumulation in aquatic systems could be improved by considering the microbial food web (bacteria and its protozoan grazers) as a previously unaccounted for pathway of contaminant transfer.

Barrett's esophagus (BE) is a premalignant condition that predisposes patients to esophageal adenocarcinoma. This risk increases with increasing dysplasia, especially in patients with BE and high-grade dysplasia. Radical esophagectomy had long been the only option for these patients; however, it has been associated with significant morbidity and mortality. Endoscopic therapies have been increasingly used as an alternative to radical esophagectomy given the minimally invasive nature and tolerability of the procedure relative to surgery. Currently, the most widely used endoscopic therapies include endoscopic mucosal resection, photodynamic therapy, CryoSpray ablation, and radiofrequency ablation. Retrospective and prospective studies on the use of each of these modalities in patients with nondysplastic BE, dysplastic BE, and early esophageal cancer have demonstrated their effectiveness in eradication of dysplasia with or without reversion of Barrett's epithelium to normal squamous epithelium of the esophagus. These modalities are well tolerated, safe, and have few side effects. Ultimately, more research is needed regarding their ability to fully displace surgical intervention as the gold standard, although at this point their role in poor operative candidates or patients seeking conservative approaches remains promising.