Acidithiobacillus ferrooxidans metabolism: from genome sequence to industrial applications

<p>Abstract</p> <p>Background</p> <p><it>Acidithiobacillus ferrooxidans </it>is a major participant in consortia of microorganisms used for the industrial recovery of copper (bioleaching or biomining). It is a chemolithoautrophic, γ-proteobacterium using energy from the oxidation of iron- and sulfur-containing minerals for growth. It thrives at extremely low pH (pH 1–2) and fixes both carbon and nitrogen from the atmosphere. It solubilizes copper and other metals from rocks and plays an important role in nutrient and metal biogeochemical cycling in acid environments. The lack of a well-developed system for genetic manipulation has prevented thorough exploration of its physiology. Also, confusion has been caused by prior metabolic models constructed based upon the examination of multiple, and sometimes distantly related, strains of the microorganism.</p> <p>Results</p> <p>The genome of the type strain <it>A. ferrooxidans </it>ATCC 23270 was sequenced and annotated to identify general features and provide a framework for <it>in silico </it>metabolic reconstruction. Earlier models of iron and sulfur oxidation, biofilm formation, quorum sensing, inorganic ion uptake, and amino acid metabolism are confirmed and extended. Initial models are presented for central carbon metabolism, anaerobic metabolism (including sulfur reduction, hydrogen metabolism and nitrogen fixation), stress responses, DNA repair, and metal and toxic compound fluxes.</p> <p>Conclusion</p> <p>Bioinformatics analysis provides a valuable platform for gene discovery and functional prediction that helps explain the activity of <it>A. ferrooxidans </it>in industrial bioleaching and its role as a primary producer in acidic environments. An analysis of the genome of the type strain provides a coherent view of its gene content and metabolic potential.</p

Two-dimensional crystallization of a histidine-tagged protein on monolayers of fluidity-enhanced Ni2+-chelating lipids

Protein two-dimensional (2D) crystallization on lipid monolayers is a powerful method for structure determination. This method has been extended using the specific and strong interaction between histidine residues (of an overexpressed protein) and Ni2+ ions tethered at the headgroup of synthetic lipids. Understanding and then improving the process of adsorption and crystallization of proteins on a lipid monolayer are prerequisites for the production of large and well-ordered crystals of any soluble or membrane His-tagged proteins. These large high-quality arrays are necessary for structural studies at high resolution. We have investigated the steps of adsorption and 2D crystallization of His-HunR using three different lipids: (i) 2-(bis-carboxymethyl-amino)-6-[2-(1,3-di-O-oleyl-glyceroxy)-acetyl-amino] hexanoic acid nickel- (II) (Ni-NTA-DOGA), which has been previously used, and two specifically designed Ni2+-chelating lipids, (ii) Ni-NTA-BB, which has two branched (B) alkyl chains and (iii) Ni-NTA-BF, a nonsymmetrical lipid with one branched (B) and one fluorinated (F) chain. These three lipids, when spread at the air-water interface, exhibit various fluidity properties. The adsorption and crystallization process have been monitored in situ and in real time using a variety of complementary techniques such as ellipsometry, shear rigidity measurements of the monolayer, and Brewster angle microscopy, and we have also developed X-ray reflectivity analysis to investigate the evolution of the electron density profile of the lipid-protein monolayer. Electron microscopy observations of the protein-lipid layers were also performed. We have found that the fluidity of the lipid monolayer has a marked influence on the rates of protein adsorption and crystallization of His-HupR. When Ni-NTA-BB is used to form the monolayer, it accelerates the process of protein adsorption and the protein crystallization is three times faster than when Ni-NTA-DOGA is used

Effect of a fluid bolus on cardiovascular collapse during tracheal intubation: A randomized clinical trial

Background: Emergency tracheal intubation of critically ill adults is frequently complicated by hypotension, cardiac arrest, or death. Whether administration of an intravenous fluid bolus reduces the risk of peri-intubation cardiovascular collapse is unknown. Methods: We conducted a multicenter, two-armed, parallel-group, unblinded randomized controlled trial at nine US sites to evaluate the effectiveness of administering a 500 ml fluid bolus during rapid sequence intubation of critically-ill adults for preventing cardiovascular collapse. By opening opaque envelopes after the decision to intubate and before induction, we randomized patients to receive either a 500 ml fluid bolus started before induction (experimental group), or no fluid bolus (control group). The primary outcome was cardiovascular collapse, defined as the composite of: new systolic blood pressure \u3c65 mmHg; new or increased vasopressor receipt between induction and two minutes after intubation; cardiac arrest within one hour of intubation; or death within one hour of intubation. Results: The data and safety monitoring board stopped the trial for futility at the first planned interim analysis, which occurred after 337 patients had been enrolled. The primary outcome of cardiovascular collapse occurred in 33 of 168 patients (19.6%) in the fluid bolus group compared with 31 of 169 patients (18.3%) in the no fluid bolus group (absolute between-group difference, 1.3% [95% CI,-7.1% to 9.7%]). Individual components of the cardiovascular collapse composite outcome were not significantly different between groups. Bag-mask ventilation between induction and laryngoscopy modified the effect of fluid bolus administration on the rate of cardiovascular collapse (P value for interaction = .01). Fluid bolus administration appeared to decrease the rate of cardiovascular collapse among patients receiving bag-mask ventilation and increase the rate of cardiovascular collapse among patients not receiving bag-mask ventilation Conclusion: Administration of an intravenous fluid bolus during emergency tracheal intubation of critically ill adults did not decrease the overall rate of cardiovascular collapse compared to no fluid bolus. The effect of fluid bolus administration on cardiovascular collapse may depend on the receipt of bag-mask ventilation during intubation. (clintrials.gov: NCT03026777