Geochemical proxies for water-soil interactions in the hyperarid Atacama Desert, Chile

The Atacama Desert is the oldest and driest non-polar desert on Earth. Millions of years of hyperaridity enabled salt accumulations through atmospheric deposition. These salts can serve as proxies to decipher the interaction between water and soil as well as to understand the habitability with changing environmental settings. Therefore, we investigated four soil profiles regarding their mineralogy, salt abundance, and sulfate stable isotopic composition. The profiles were located along an elevation transect in the hyperarid region southeast of Antofagasta, Chile. The two lower sites situated on the distal parts of inactive alluvial fan deposits were subject to occasional fog occurrences. The upper steeper-sloped sites experienced no fog but are subject to minimal erosion. In all soil profiles, sulfates are the dominant salts showing a downward transition from gypsum to anhydrite that is accompanied by an increase of highly soluble salts and a decrease of sulfate δ34S and δ18O values. These trends are consistent with downward directed water infiltration during rare rain events causing salt dissolution followed by precipitation within the deeper soil column. This conclusion is also supported by our Rayleigh fractionation model. We attribute the presence of anhydrite at > 40 cm depth to the cooccurrence of nitrate and chloride salts, which decreases water activity during sulfate precipitation and therefore drives anhydrite formation. Along the elevation transect, the total salt inventories of each profile show a trend for nitrates and chlorides concentration decreasing with elevation. This observation together with the sulfate stable isotopes indicates a fog-independent source and suggests remobilization of soluble salts through enhanced wash out from hillslopes to alluvial fans. These findings are essential for assessing the long-term regional habitability of hyperarid environments and have also relevance for Mars.EC/FP7/339231/EU/Habitability of Martian Environments: Exploring the Physiological and Environmental Limits of Life/HOM

Construction and characterization of BsGDH-CatIB variants and application as robust and highly active redox cofactor regeneration module for biocatalysis

BACKGROUND: Catalytically active inclusion bodies (CatIBs) are known for their easy and cost efficient production, recyclability as well as high stability and provide an alternative purely biological technology for enzyme immobilization. Due to their ability to self-aggregate in a carrier-free, biodegradable form, no further laborious immobilization steps or additional reagents are needed. These advantages put CatIBs in a beneficial position in comparison to traditional immobilization techniques. Recent studies outlined the impact of cooperative effects of the linker and aggregation inducing tag on the activity level of CatIBs, requiring to test many combinations to find the best performing CatIB variant. RESULTS: Here, we present the formation of 14 glucose dehydrogenase CatIB variants of Bacillus subtilis, a well-known enzyme in biocatalysis due to its capability for substrate coupled regeneration of reduced cofactors with cheap substrate glucose. Nine variants revealed activity, with highest productivity levels for the more rigid PT-Linker combinations. The best performing CatIB, BsGDH-PT-CBDCell, was characterized in more detail including long-term storage at −20 °C as well as NADH cofactor regeneration performance in repetitive batch experiments with CatIB recycling. After freezing, BsGDH-PT-CBDCell CatIB only lost approx. 10% activity after 8 weeks of storage. Moreover, after 11 CatIB recycling cycles in repetitive batch operation 80% of the activity was still present. CONCLUSIONS: This work presents a method for the effective formation of a highly active and long-term stable BsGDH-CatIB as an immobilized enzyme for robust and convenient NADH regeneration. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12934-022-01816-2

Control of parallelized bioreactors II: probabilistic quantification of carboxylic acid reductase activity for bioprocess optimization

Autonomously operated parallelized mL-scale bioreactors are considered the key to reduce bioprocess development cost and time. However, their application is often limited to products with very simple analytics. In this study, we investigated enhanced protein expression conditions of a carboxyl reductase from Nocardia otitidiscaviarum in E. coli. Cells were produced with exponential feeding in a L-scale bioreactor. After the desired cell density for protein expression was reached, the cells were automatically transferred to 48 mL-scale bioreactors operated by a liquid handling station where protein expression studies were conducted. During protein expression, the feed rate and the inducer concentration was varied. At the end of the protein expression phase, the enzymatic activity was estimated by performing automated whole-cell biotransformations in a deep-well-plate. The results were analyzed with hierarchical Bayesian modelling methods to account for the biomass growth during the biotransformation, biomass interference on the subsequent product assay, and to predict absolute and specific enzyme activities at optimal expression conditions. Lower feed rates seemed to be beneficial for high specific and absolute activities. At the optimal investigated expression conditions an activity of [Formula: see text] was estimated with a [Formula: see text] credible interval of [Formula: see text] . This is about 40-fold higher than the highest published data for the enzyme under investigation. With the proposed setup, 192 protein expression conditions were studied during four experimental runs with minimal manual workload, showing the reliability and potential of automated and digitalized bioreactor systems

Topical azithromycin for the prevention of Lyme borreliosis: a randomised, placebo-controlled, phase 3 efficacy trial

Background Lyme borreliosis develops in 1-5% of individuals bitten by ticks, but with a diagnostic gap affecting up to 30% of patients, a broadly applicable pharmacological prevention strategy is needed. Topical azithromycin effectively eradicated Borrelia burgdorferi sensu lato from the skin in preclinical studies. We assessed its efficacy in human beings. Methods In this randomised, double-blind, placebo-controlled, multicentre trial done in 28 study sites in Germany and Austria, adults were equally assigned to receive topical 10% azithromycin or placebo twice daily for 3 consecutive days, within 72 h of a tick bite being confirmed. Randomisation numbers, which were stratified by study site, were accessed in study centres via an interactive voice-response system, by pharmacists not involved in the study. The primary outcome was the number of treatment failures, defined as erythema migrans, seroconversion, or both, in participants who were seronegative at baseline, had no further tick bites during the study, and had serology results available at 8 weeks (intention-to-treat [ITT] population). This study is registered with EudraCT, number 2011-000117-39. Findings Between July 7, 2011, and Dec 3, 2012, 1371 participants were randomly assigned to treatment, of whom 995 were included in the ITT population. The trial was stopped early because an improvement in the primary endpoint in the group receiving azithromycin was not reached. At 8 weeks, 11 (2%) of 505 in the azithromycin group and 11 (2%) of 490 in the placebo group had treatment failure (odds ratio 0.97, 95% CI 0 42-2 26, p=0.47). Topical azithromycin was well tolerated. Similar numbers of patients had adverse events in the two groups (175 [26%] of 505 vs 177 [26%] of 490, p=0.87), and most adverse events were mild. Interpretation Topical azithromycin was well tolerated and had a good safety profile. Inclusion of asymptomatic seroconversion into the primary efficacy analysis led to no prevention effect with topical azithromycin. Adequately powered studies assessing only erythema migrans should be considered. A subgroup analysis in this study suggested that topical azithromycin reduces erythema migrans after bites of infected ticks