Iron-Fueled Life in the Continental Subsurface: Deep Mine Microbial Observatory, South Dakota, USA.

Iron-bearing minerals are key components of the Earth's crust and potentially critical energy sources for subsurface microbial life. The Deep Mine Microbial Observatory (DeMMO) is situated in a range of iron-rich lithologies, and fracture fluids here reach concentrations as high as 8.84 mg/liter. Iron cycling is likely an important process, given the high concentrations of iron in fracture fluids and detection of putative iron-cycling taxa via marker gene surveys. However, a previous metagenomic survey detected no iron cycling potential at two DeMMO localities. Here, we revisited the potential for iron cycling at DeMMO using a new metagenomic data set including all DeMMO sites and FeGenie, a new annotation pipeline that is optimized for the detection of iron cycling genes. We annotated functional genes from whole metagenomic assemblies and metagenome-assembled genomes and characterized putative iron cycling pathways and taxa in the context of local geochemical conditions and available metabolic energy estimated from thermodynamic models. We reannotated previous metagenomic data, revealing iron cycling potential that was previously missed. Across both metagenomic data sets, we found that not only is there genetic potential for iron cycling at DeMMO, but also, iron is likely an important source of energy across the system. In response to the dramatic differences we observed between annotation approaches, we recommend the use of optimized pipelines where the detection of iron cycling genes is a major goal. IMPORTANCE We investigated iron cycling potential among microbial communities inhabiting iron-rich fracture fluids to a depth of 1.5 km in the continental crust. A previous study found no iron cycling potential in the communities despite the iron-rich nature of the system. A new tool for detecting iron cycling genes was recently published, which we used on a new data set. We combined this with a number of other approaches to get a holistic view of metabolic strategies across the communities, revealing iron cycling to be an important process here. In addition, we used the tool on the data from the previous study, revealing previously missed iron cycling potential. Iron is common in continental crust; thus, our findings are likely not unique to our study site. Our new view of important metabolic strategies underscores the importance of choosing optimized tools for detecting the potential for metabolisms like iron cycling that may otherwise be missed.

The role of anticholinergics in bronchoscopy. A randomized clinical trial.

BACKGROUND: Anticholinergic medications have been utilized frequently prior to bronchoscopy and are thought to facilitate the drying of secretions to limit the amount of required topical anesthetic on the airway mucosa, prevent cardiac arrhythmias during the procedure, and increase patient comfort. OBJECTIVE: To determine if atropine or glycopyrrolate, two anticholinergic agents utilized most frequently in this setting, have any significant role for this purpose. DESIGN: Double-blind, placebo-controlled study, in which patients were randomly selected to receive atropine (0.01 mg/kg body weight, IM injection), glycopyrrolate (0.005 mg/kg, IM injection), or saline solution placebo (approximately 2 mL, IM injection) 15 to 45 min prior to being sedated with midazolam until judged to be lightly sedated. SETTING: A large academic teaching hospital in the midwestern United States. PARTICIPANTS: Two hundred seventeen outpatients referred for bronchoscopy who satisfied inclusion and exclusion criteria. MEASUREMENTS AND RESULTS: Using a modified visual analog scale (0 to 100 mm), the bronchoscopist and the nurse anesthetist estimated the antisialagogic effect, effectiveness in cough suppression, and overall patient comfort during the procedure. The patients completed a similar questionnaire after recovering from the procedure. Patients were also monitored for complications (cardiac arrhythmias, oxygen desaturation, hypertension, wheezing, or coughing severe enough to curtail the procedure). There was no significant difference found among atropine, glycopyrrolate, and placebo for the primary end point of secretion control. In addition, there was no difference found between either medication and placebo for effectiveness of cough suppression, amount of topical anesthetic used, complication rates, or overall patient comfort. CONCLUSION: The use of anticholinergic agents prior to bronchoscopy did not affect performance of bronchoscopy or complication rates, and there was no appreciable benefit from the resultant reduction in airway secretions in a population of patients receiving concurrent sedation with benzodiazepines.