Complex Microbial Communities Drive Iron and Sulfur Cycling in Arctic Fjord Sediments.

Glacial retreat is changing biogeochemical cycling in the Arctic, where glacial runoff contributes iron for oceanic shelf primary production. We hypothesize that in Svalbard fjords, microbes catalyze intense iron and sulfur cycling in low-organic-matter sediments. This is because low organic matter limits sulfide generation, allowing iron mobility to the water column instead of precipitation as iron monosulfides. In this study, we tested this with high-depth-resolution 16S rRNA gene libraries in the upper 20 cm at two sites in Van Keulenfjorden, Svalbard. At the site closer to the glaciers, iron-reducing Desulfuromonadales, iron-oxidizing Gallionella and Mariprofundus, and sulfur-oxidizing Thiotrichales and Epsilonproteobacteria were abundant above a 12-cm depth. Below this depth, the relative abundances of sequences for sulfate-reducing Desulfobacteraceae and Desulfobulbaceae increased. At the outer station, the switch from iron-cycling clades to sulfate reducers occurred at shallower depths (∼5 cm), corresponding to higher sulfate reduction rates. Relatively labile organic matter (shown by δ13C and C/N ratios) was more abundant at this outer site, and ordination analysis suggested that this affected microbial community structure in surface sediments. Network analysis revealed more correlations between predicted iron- and sulfur-cycling taxa and with uncultured clades proximal to the glacier. Together, these results suggest that complex microbial communities catalyze redox cycling of iron and sulfur, especially closer to the glacier, where sulfate reduction is limited due to low availability of organic matter. Diminished sulfate reduction in upper sediments enables iron to flux into the overlying water, where it may be transported to the shelf.IMPORTANCE Glacial runoff is a key source of iron for primary production in the Arctic. In the fjords of the Svalbard archipelago, glacial retreat is predicted to stimulate phytoplankton blooms that were previously restricted to outer margins. Decreased sediment delivery and enhanced primary production have been hypothesized to alter sediment biogeochemistry, wherein any free reduced iron that could potentially be delivered to the shelf will instead become buried with sulfide generated through microbial sulfate reduction. We support this hypothesis with sequencing data that showed increases in the relative abundance of sulfate reducing taxa and sulfate reduction rates with increasing distance from the glaciers in Van Keulenfjorden, Svalbard. Community structure was driven by organic geochemistry, suggesting that enhanced input of organic material will stimulate sulfate reduction in interior fjord sediments as glaciers continue to recede.

Microaerophilic Fe(II)-Oxidizing Zetaproteobacteria Isolated from Low-Fe Marine Coastal Sediments: Physiology and Composition of Their Twisted Stalks.

Microaerophilic Fe(II) oxidizers are commonly found in habitats containing elevated Fe(II) and low O2 concentrations and often produce characteristic Fe mineral structures, so-called twisted stalks or tubular sheaths. Isolates originating from freshwater habitats are all members of the Betaproteobacteria, while isolates from marine habitats belong almost exclusively to the Zetaproteobacteria So far, only a few isolates of marine microaerophilic Fe(II) oxidizers have been described, all of which are obligate microaerophilic Fe(II) oxidizers and have been thought to be restricted to Fe-rich systems. Here, we present two new isolates of marine microaerophilic Fe(II)-oxidizing Zetaproteobacteria that originate from typical coastal marine sediments containing only low Fe concentrations (2 to 11 mg of total Fe/g of sediment [dry weight]; 70 to 100 µM dissolved Fe2+ in the porewater). The two novel Zetaproteobacteria share characteristic physiological properties of the Zetaproteobacteria group, even though they come from low-Fe environments: the isolates are obligate microaerophilic Fe(II) oxidizers and, like most isolated Zetaproteobacteria, they produce twisted stalks. We found a low organic carbon content in the stalks (∼0.3 wt%), with mostly polysaccharides and saturated aliphatic chains (most likely lipids). The Fe minerals in the stalks were identified as lepidocrocite and possibly ferrihydrite. Immobilization experiments with Ni2+ showed that the stalks can function as a sink for trace metals. Our findings show that obligate microaerophilic Fe(II) oxidizers belonging to the Zetaproteobacteria group are not restricted to Fe-rich environments but can also be found in low-Fe marine environments, which increases their overall importance for the global biogeochemical Fe cycle.IMPORTANCE So far, only a few isolates of benthic marine microaerophilic Fe(II) oxidizers belonging to the Zetaproteobacteria exist, and most isolates were obtained from habitats containing elevated Fe concentrations. Consequently, it was thought that these microorganisms are important mainly in habitats with high Fe concentrations. The two novel isolates of Zetaproteobacteria that are presented in the present study were isolated from typical coastal marine sediments that do not contain elevated Fe concentrations. This increases the knowledge about possible habitats in which Zetaproteobacteria can exist. Furthermore, we show that the physiology and the typical organo-mineral structures (twisted stalks) that are produced by the isolates do not notably differ from the physiology and the cell-mineral structures of isolates from environments with high Fe concentrations. We also showed that the organo-mineral structures can function as a sink for trace metals.

Competency-based orientation for clinical nurse educators.

The orientation process highlights entry into new roles and responsibilities. The attainment of competence in this process can be enhanced through the appropriate identification of requisite knowledge and skills and the use of creative tools to establish an organized process and documentation of progress. Clinical educators in acute care settings require an orientation program that incorporates both clinical and educational components. Formal communication between a new hire and preceptor and subsequent documentation for both administrative and peer review provide increased accountability. Therefore, a variety of strategies, often melding the clinical and teaching roles, becomes crucial to a successful orientation program.

Management of stage I-B, II-A, and II-B carcinoma of the cervix with high-dose-rate brachytherapy: initial results of an institutional clinical trial.

In 1989, the University of Miami began a program incorporating high-dose-rate (HDR) brachytherapy into the definitive treatment of patients with invasive carcinoma of the cervix. Patients received an average total dose to point A of 5,511 cGy (range 4,280-6,360 cGy) in an average of 57 days (range 39-84 days). An analysis of the first 24 cases found 11 FIGO Stage I-B, four Stage II-A, and nine Stage II-B tumors. At the end of all radiation therapy, 19/24 patients' tumors (79.2%) had undergone a clinical complete response (CR). With median follow-up of 26 months (range 14-63 months), three have relapsed locally, two regionally, and six in extrapelvic sites. Almost two-thirds of all failures occurred in patients with tumors >4 cm, who also took more than 8 weeks to complete their treatment. Overall 2-year actuarial survival for the entire study group is approximately 74%. A univariate analysis determined that clinical stage (P = 0.02), overall treatment time (P = 0.03), tumor size (P = 0.05), and response at the end of therapy (P = 0.005) were significant prognostic factors. Multivariate analysis showed that tumor response to therapy was the most important prognosticator of outcome (P = 0.001). Besides five cases of apical vaginal stenosis, there have been no reported chronic complications in this cohort of patients. A prospectively randomized trial is recommended to compare the efficacy of HDR vs. low-dose-rate brachytherapy in cervical carcinoma.

Launching a multidisciplinary staff development program for liver transplantation.

This article describes a collaborative effort between specialty areas at a large urban medical center to develop a comprehensive liver transplant educational program. The historical overview, needs assessment, and program planning are discussed. The implementation, planning, and evaluation phases are examined. The process presented here can serve as a framework for clinical educators confronted with major new initiatives.

Coenzyme F430 as a possible catalyst for the reductive dehalogenation of chlorinated C1 hydrocarbons in methanogenic bacteria.

Corrinoids, such as aquocobalamin, methylcobalamin, and (cyanoaquo)cobinamide, catalyze the reductive dehalogenation of CCl4 with titanium(III) citrate as the electron donor [Krone et al. (1989) Biochemistry 28, 4908-4914]. We report here that this reaction is also effectively mediated by the nickel-containing porphinoid, coenzyme F430, found in methanogenic bacteria. Chloroform, methylene chloride, methyl chloride, and methane were detected as intermediates and products. Ethane was formed in trace amounts, and several as yet unidentified nonvolatile compounds were also generated. The rate of dehalogenation decreased in the series of CCl4, CHCl3, and CH2Cl2. With coenzyme F430 as the catalyst, the reduction of CH3Cl to CH4 proceeded more than 50 times faster than with aquocobalamin. Cell suspensions of Methanosarcina barkeri were found to catalyze the reductive dehalogenation of CCl4 with CO as the electron donor (E'0 = -0.524 V). Methylene chloride was the main end product. The kinetics of CHCl3 and CH2Cl2 formation from CCl4 were similar to those with coenzyme F430 or aquocobalamin as catalysts and titanium(III) citrate as the reductant.