Comparison of test strip, conductivity, and novel smartphone digital image colorimetry methods for field assessment of soil chloride and salinity.

Understanding the extent of salt-affected soils is important in agriculture for irrigation, crop selection and land management, and affordable smartphone-based techniques can broaden access to environmental analysis in resource-limited settings. A novel smartphone-based Digital Image Colorimetry (DImC) technique using colorimetric chloride test strips has been developed and compared to 3 other field techniques (direct soil conductivity (Csoil), soil extract solution conductivity (Cext), titration test strips (TS)) and 1 lab-based method (chloride analyser (CA)) for the assessment of soil salinity. A survey of soils from a coastal saltmarsh and neighbouring farmland was conducted in Southwest Scotland and a rapid sample preparation method suitable for in-field use was evaluated. Comparison of each method with the reference method (CA) using correlation plots, Bland-Altman plots, and concordance correlation coefficients, showed that the accuracy and precision of the methods decreased in the order Cext > DImC ≃ TS > Csoil. The novel DImC method had good accuracy, although the limit of detection (LOD = 20.30 mg L-1) and precision was poorer than Cext. The analysis of field-wet soils enabled a rapid estimate of soil Cl- in approximately 6 minutes and spatially interpolated maps of soil Cl- concentration, prepared using smartphone location data, identified areas of elevated soil salinity. Each field analysis method had specific benefits, and the low cost, portability and lack of specialist equipment required for the DImC method demonstrated suitability for use in agriculture, citizen science or conservation settings where resources may be limited. The example presented demonstrates how smartphones may be used to broaden access to environmental analysis techniques.

The million-molecule challenge: a moonshot project to rapidly advance longevity intervention discovery.

Targeting aging is the future of twenty-first century preventative medicine. Small molecule interventions that promote healthy longevity are known, but few are well-developed and discovery of novel, robust interventions has stagnated. To accelerate longevity intervention discovery and development, high-throughput systems are needed that can perform unbiased drug screening and directly measure lifespan and healthspan metrics in whole animals. C. elegans is a powerful model system for this type of drug discovery. Combined with automated data capture and analysis technologies, truly high-throughput longevity drug discovery is possible. In this perspective, we propose the "million-molecule challenge", an effort to quantitatively assess 1,000,000 interventions for longevity within five years. The WormBot-AI, our best-in-class robotics and AI data analysis platform, provides a tool to achieve the million-molecule challenge for pennies per animal tested.

Taurine deficiency as a driver of aging.

Aging is associated with changes in circulating levels of various molecules, some of which remain undefined. We find that concentrations of circulating taurine decline with aging in mice, monkeys, and humans. A reversal of this decline through taurine supplementation increased the health span (the period of healthy living) and life span in mice and health span in monkeys. Mechanistically, taurine reduced cellular senescence, protected against telomerase deficiency, suppressed mitochondrial dysfunction, decreased DNA damage, and attenuated inflammaging. In humans, lower taurine concentrations correlated with several age-related diseases and taurine concentrations increased after acute endurance exercise. Thus, taurine deficiency may be a driver of aging because its reversal increases health span in worms, rodents, and primates and life span in worms and rodents. Clinical trials in humans seem warranted to test whether taurine deficiency might drive aging in humans.

Deficiency of the RNA-binding protein Cth2 extends yeast replicative lifespan by alleviating its repressive effects on mitochondrial function.

Iron dyshomeostasis contributes to aging, but little information is available about the molecular mechanisms. Here, we provide evidence that in Saccharomyces cerevisiae, aging is associated with altered expression of genes involved in iron homeostasis. We further demonstrate that defects in the conserved mRNA-binding protein Cth2, which controls stability and translation of mRNAs encoding iron-containing proteins, increase lifespan by alleviating its repressive effects on mitochondrial function. Mutation of the conserved cysteine residue in Cth2 that inhibits its RNA-binding activity is sufficient to confer longevity, whereas Cth2 gain of function shortens replicative lifespan. Consistent with its function in RNA degradation, Cth2 deficiency relieves Cth2-mediated post-transcriptional repression of nuclear-encoded components of the electron transport chain. Our findings uncover a major role of the RNA-binding protein Cth2 in the regulation of lifespan and suggest that modulation of iron starvation signaling can serve as a target for potential aging interventions.

Evidence that conserved essential genes are enriched for pro-longevity factors.

At the cellular level, many aspects of aging are conserved across species. This has been demonstrated by numerous studies in simple model organisms like Saccharomyces cerevisiae, Caenorhabdits elegans, and Drosophila melanogaster. Because most genetic screens examine loss of function mutations or decreased expression of genes through reverse genetics, essential genes have often been overlooked as potential modulators of the aging process. By taking the approach of increasing the expression level of a subset of conserved essential genes, we found that 21% of these genes resulted in increased replicative lifespan in S. cerevisiae. This is greater than the ~ 3.5% of genes found to affect lifespan upon deletion, suggesting that activation of essential genes may have a relatively disproportionate effect on increasing lifespan. The results of our experiments demonstrate that essential gene overexpression is a rich, relatively unexplored means of increasing eukaryotic lifespan.

Organic complexation of U(VI) in reducing soils at a natural analogue site: Implications for uranium transport.

Understanding the long-term fate, stability, and bioavailability of uranium (U) in the environment is important for the management of nuclear legacy sites and radioactive wastes. Analysis of U behavior at natural analogue sites permits evaluation of U biogeochemistry under conditions more representative of long-term equilibrium. Here, we have used bulk geochemical and microbial community analysis of soils, coupled with X-ray absorption spectroscopy and µ-focus X-ray fluorescence mapping, to gain a mechanistic understanding of the fate of U transported into an organic-rich soil from a pitchblende vein at the UK Needle's Eye Natural Analogue site. U is highly enriched in the Needle's Eye soils (∼1600 mg kg-1). We show that this enrichment is largely controlled by U(VI) complexation with soil organic matter and not U(VI) bioreduction. Instead, organic-associated U(VI) seems to remain stable under microbially-mediated Fe(III)-reducing conditions. U(IV) (as non-crystalline U(IV)) was only observed at greater depths at the site (>25 cm); the soil here was comparatively mineral-rich, organic-poor, and sulfate-reducing/methanogenic. Furthermore, nanocrystalline UO2, an alternative product of U(VI) reduction in soils, was not observed at the site, and U did not appear to be associated with Fe-bearing minerals. Organic-rich soils appear to have the potential to impede U groundwater transport, irrespective of ambient redox conditions.

Loss of vacuolar acidity results in iron-sulfur cluster defects and divergent homeostatic responses during aging in Saccharomyces cerevisiae.

The loss of vacuolar/lysosomal acidity is an early event during aging that has been linked to mitochondrial dysfunction. However, it is unclear how loss of vacuolar acidity results in age-related dysfunction. Through unbiased genetic screens, we determined that increased iron uptake can suppress the mitochondrial respiratory deficiency phenotype of yeast vma mutants, which have lost vacuolar acidity due to genetic disruption of the vacuolar ATPase proton pump. Yeast vma mutants exhibited nuclear localization of Aft1, which turns on the iron regulon in response to iron-sulfur cluster (ISC) deficiency. This led us to find that loss of vacuolar acidity with age in wild-type yeast causes ISC defects and a DNA damage response. Using microfluidics to investigate aging at the single-cell level, we observe grossly divergent trajectories of iron homeostasis within an isogenic and environmentally homogeneous population. One subpopulation of cells fails to mount the expected compensatory iron regulon gene expression program, and suffers progressively severe ISC deficiency with little to no activation of the iron regulon. In contrast, other cells show robust iron regulon activity with limited ISC deficiency, which allows extended passage and survival through a period of genomic instability during aging. These divergent trajectories suggest that iron regulation and ISC homeostasis represent a possible target for aging interventions.