Given the challenges to life at low pH, an analysis of inorganic sulfur compound (ISC) oxidation was initiated in the chemolithoautotrophic extremophile Acidithiobacillus caldus. A. caldus is able to metabolize elemental sulfur and a broad range of ISCs. It has been implicated in the production of environmentally damaging acidic solutions as well as participating in industrial bioleaching operations where it forms part of microbial consortia used for the recovery of metal ions. Based upon the recently published A. caldus type strain genome sequence, a bioinformatic reconstruction of elemental sulfur and ISC metabolism predicted genes included: sulfide–quinone reductase (sqr), tetrathionate hydrolase (tth), two sox gene clusters potentially involved in thiosulfate oxidation (soxABXYZ), sulfur oxygenase reductase (sor), and various electron transport components. RNA transcript profiles by semi quantitative reverse transcription PCR suggested up-regulation of sox genes in the presence of tetrathionate. Extensive gel based proteomic comparisons of total soluble and membrane enriched protein fractions during growth on elemental sulfur and tetrathionate identified differential protein levels from the two Sox clusters as well as several chaperone and stress proteins up-regulated in the presence of elemental sulfur. Proteomics results also suggested the involvement of heterodisulfide reductase (HdrABC) in A. caldus ISC metabolism. A putative new function of Hdr in acidophiles is discussed. Additional proteomic analysis evaluated protein expression differences between cells grown attached to solid, elemental sulfur versus planktonic cells. This study has provided insights into sulfur metabolism of this acidophilic chemolithotroph and gene expression during attachment to solid elemental sulfur.

Gene transcription (microarrays) and protein levels (proteomics) were compared in cultures of the acidophilic chemolithotroph Acidithiobacillus ferrooxidans grown on elemental sulfur as the electron donor under aerobic and anaerobic conditions, using either molecular oxygen or ferric iron as the electron acceptor, respectively. No evidence supporting the role of either tetrathionate hydrolase or arsenic reductase in mediating the transfer of electrons to ferric iron (as suggested by previous studies) was obtained. In addition, no novel ferric iron reductase was identified. However, data suggested that sulfur was disproportionated under anaerobic conditions, forming hydrogen sulfide via sulfur reductase and sulfate via heterodisulfide reductase and ATP sulfurylase. Supporting physiological evidence for H 2 S production came from the observation that soluble Cu 2؉ included in anaerobically incubated cultures was precipitated (seemingly as CuS). Since H 2 S reduces ferric iron to ferrous in acidic medium, its production under anaerobic conditions indicates that anaerobic iron reduction is mediated, at least in part, by an indirect mechanism. Evidence was obtained for an alternative model implicating the transfer of electrons from S 0 to Fe 3؉ via a respiratory chain that includes a bc 1 complex and a cytochrome c. Central carbon pathways were upregulated under aerobic conditions, correlating with higher growth rates, while many Calvin-Benson-Bassham cycle components were upregulated during anaerobic growth, probably as a result of more limited access to carbon dioxide. These results are important for understanding the role of A. ferrooxidans in environmental biogeochemical metal cycling and in industrial bioleaching operations.

Ziel: Ziel der Studie war die Evaluierung der Präva-lenz der KHK bei männlichen Marathonläufern mittleren Alters mittels Dual Source cCTA (DSCTA). Material und Methoden: 50 Marathonläufer (52,7 ± 5,9 Jahre) wurden zusätzlich zur sportmedizinischen Routinediagnostik mittels DSCTA einschließlich Calcium-Scoring (CS) untersucht. Das CS wurde bei allen Personen im high-pitchModus (hpDSCTA), die CTA bei 21 Personen im hpDSCTA und 29 Personen im sequentiellen "step-and-shot"-Modus (sDSCTA) durchgeführt. Die effektive Dosis (ED) wurde für beide Scanverfahren bestimmt. Der Risikofaktor für koronare Ereignisse wurde basierend auf Standardrisikofaktoren mittels des PROCAM-Scores berechnet. Der Koronarstatus wurde wie folgt klassifiziert: 1. keine KHK (CS = 0, keine Koronarplaques), 2. milde Koronarsklerose (CS> 0, Stenose < 50 %), 3. moderate Koronarsklerose (CS > 0, Stenose > 50 %) 4. signifikante KHK (CS > 0, Stenose > 75 %). Ergebnisse: Der mediane PROCAM-Score betrug 1,85 ± 1,56 %. 26 von 50 Marathonläufern hatten keine KHK. 1 Person hatte eine signifikante KHK, 3 Personen eine moderate sowie 20 eine milde Koronarsklerose. Die Laufband-Ergometrie konnte bei keinem Sportler Koronarischämien nachweisen. Als Faktoren für ein erhöhtes KHK-Risiko konnten Alter, Blutdruck, persönliche Mindestzeit, familiäre Anamnese und der PROCAM-Score identifiziert werden. Die mediane ED für die DSCTA lag bei 1,259 ± 0,542 mSv. Bei der hpDSCTA war die ED im Vergleich zur sDSCTA signifikant niedriger (0,762 vs. 1,618 mSv, p < 0,0001). Schlussfolgerung: Bei fast 50 % der asymptomatischen Marathonläufer über 45 Jahren kann mittels cCTA eine Koronarsklerose nachgewiesen werden. Bei 24 % dieser Probanden waren die Plaques in den proximalen Abschnitten der Koronararterien lokalisiert. Tatsächlich leidet jedoch nur ein kleiner Anteil dieser Personen an einer obstruktiven KHK. Abstract !Purpose: To evaluate the prevalence of coronary artery disease (CAD) in middle-aged, male marathon runners using coronary dual source CT angiography (DSCTA). Materials and Methods: 50 male marathon runners older than 45 years (mean age: 52.7, standard deviation: 5.9 years, range: 45 to 67 years) received DSCTA including calcium scoring (CS) in addition to standard pre-participation screening. Based on standard risk factors, the risk for coronary events was calculated using the PROCAM score. Coronary status was defined using the following system: 1. absence of CAD (CS zero, no coronary plaques) 2. mild coronary atherosclerosis (CS > 0, coronary plaques with luminal narrowing < 50 %), 3. moderate coronary atherosclerosis (CS > 0, luminal narrowing > 50 %), 4. significant CAD (CS > 0, luminal narrowing > 75 %). Results: The mean PROCAM score was 1.85 % (standard deviation = 1.56, range 0.39 to 8.47 %). 26/50 marathon runners had no atherosclerosis. 1 of the remaining 24 participants had significant CAD, 3 had moderate coronary atherosclerosis and 20 had mild coronary atherosclerosis. Treadmill exercise testing was unremarkable in terms of myocardial ischemia in all p...

This large international radiation dose survey demonstrates considerable reduction of radiation exposure in coronary CTA during the last decade. However, the large inter-site variability in radiation exposure underlines the need for further site-specific training and adaptation of contemporary cardiac scan protocols.

• Dual-source CT (DSCT) allows for single- and dual-energy image acquisition. • Dual-energy acquisition does not increase the radiation dose in abdominal DSCT. • Third-generation DSCT shows improved dose efficiency compared to second-generation DSCT. • Dose-independent figure-of-merit image contrast was highest with third-generation dual-energy DSCT. • Third-generation DSCT shows improved dose efficiency for SECT and DECT.

High concentrations of chloride ions inhibit the growth of acidophilic microorganisms used in biomining, a problem particularly relevant to Western Australian and Chilean biomining operations. Despite this, little is known about the mechanisms acidophiles adopt in order to tolerate high chloride ion concentrations. This study aimed to investigate the impact of increasing concentrations of chloride ions on the population dynamics of a mixed culture during pyrite bioleaching and apply proteomics to elucidate how two species from this mixed culture alter their proteomes under chloride stress. A mixture consisting of well-known biomining microorganisms and an enrichment culture obtained from an acidic saline drain were tested for their ability to bioleach pyrite in the presence of 0, 3.5, 7, and 20 g L(-1) NaCl. Microorganisms from the enrichment culture were found to out-compete the known biomining microorganisms, independent of the chloride ion concentration. The proteomes of the Gram-positive acidophile Acidimicrobium ferrooxidans and the Gram-negative acidophile Acidithiobacillus caldus grown in the presence or absence of chloride ions were investigated. Analysis of differential expression showed that acidophilic microorganisms adopted several changes in their proteomes in the presence of chloride ions, suggesting the following strategies to combat the NaCl stress: adaptation of the cell membrane, the accumulation of amino acids possibly as a form of osmoprotectant, and the expression of a YceI family protein involved in acid and osmotic-related stress.

Zinc can occur in extremely high concentrations in acidic, heavy metal polluted environments inhabited by acidophilic prokaryotes. Although these organisms are able to thrive in such severely contaminated ecosystems their resistance mechanisms have not been well studied. Bioinformatic analysis of a range of acidophilic bacterial and archaeal genomes identified homologues of several known zinc homeostasis systems. These included primary and secondary transporters, such as the primary heavy metal exporter ZntA and Nramp super-family secondary importer MntH. Three acidophilic model microorganisms, the archaeon 'Ferroplasma acidarmanus', the Gram negative bacterium Acidithiobacillus caldus, and the Gram positive bacterium Acidimicrobium ferrooxidans, were selected for detailed analyses. Zinc speciation modeling of the growth media demonstrated that a large fraction of the free metal ion is complexed, potentially affecting its toxicity. Indeed, many of the putative zinc homeostasis genes were constitutively expressed and with the exception of 'F. acidarmanus' ZntA, they were not up-regulated in the presence of excess zinc. Proteomic analysis revealed that zinc played a role in oxidative stress in At. caldus and Am. ferrooxidans. Furthermore, 'F. acidarmanus' kept a constant level of intracellular zinc over all conditions tested whereas the intracellular levels increased with increasing zinc exposure in the remaining organisms.

2 J. MAGN. RESON. IMAGING 2017;45:1429-1437.