Radioactivity as a driver of bacterial community composition in naturally radioactive mineral springs in the French Massif Central.

Some natural environments on Earth are characterised by high levels of radiation, including naturally radioelement enriched mineral springs in the French Massif Central. Therefore, naturally radioactive mineral springs are interesting ecosystems for understanding how bacterial populations in these springs have adapted to high levels of natural and chronic radioactivity over the very long term. The aim of this study was to analyse the bacterial communities of sediments from five naturally radioactive mineral springs in the French Massif Central, sampled in autumn 2019 and spring 2020, and to observe whether radionuclides, compared to other physicochemical parameters, are drivers of the bacterial community structuring in these extreme environments. Physicochemical measurements showed that two springs, Dourioux and Montagne had high radioelement concentrations/activities (uranium, thorium and radon). Analysis of the structure of the bacterial communities, by next generation sequencing based on 16S rRNA gene sequencing, showed that the presence of radionuclides in Dourioux and Montagne, did not lead to a reduction in bacterial diversity and richness compared to the other springs. However, Dourioux and Montagne were characterised by specific bacterial populations, whose presence correlates with the radioelement concentrations/activities measured in these springs. This suggests that radioelements could partly explain the structuring of bacterial communities in these springs. In addition, several of these operational taxonomic units (OTUs) specific to Dourioux and Montagne, mainly affiliated to Proteobacteria, Firmicutes, Acidobacteria, Actinobacteria, and Bacteroidetes, could be involved in the biogeochemistry of radionuclides through different mechanisms (biosorption, biomineralisation, bioaccumulation, and bioreduction), which would allow the development of other bacterial species sensitive to these metals/radioelements. In particular, the co-occurrence of sulphate and/or iron-reducing bacteria, capable of bioreducing uranium, with fermentative bacteria, releasing sources of organic carbons, reflects associations of bacteria with complementary functions that allow them to grow in this peculiar environment and maintain a high diversity in these extreme environments. This study has provided a better understanding of the structuring of bacterial communities exposed to ionising radiation for thousands of years in naturally radioactive environments.

Assessing radiation dosimetry for microorganisms in naturally radioactive mineral springs using GATE and Geant4-DNA Monte Carlo simulations.

Mineral springs in Massif Central, France can be characterized by higher levels of natural radioactivity in comparison to the background. The biota in these waters is constantly under radiation exposure mainly from the α-emitters of the natural decay chains, with 226Ra in sediments ranging from 21 Bq/g to 43 Bq/g and 222Rn activity concentrations in water up to 4600 Bq/L. This study couples for the first time micro- and nanodosimetric approaches to radioecology by combining GATE and Geant4-DNA to assess the dose rates and DNA damages to microorganisms living in these naturally radioactive ecosystems. It focuses on unicellular eukaryotic microalgae (diatoms) which display an exceptional abundance of teratological forms in the most radioactive mineral springs in Auvergne. Using spherical geometries for the microorganisms and based on γ-spectrometric analyses, we evaluate the impact of the external exposure to 1000 Bq/L 222Rn dissolved in the water and 30 Bq/g 226Ra in the sediments. Our results show that the external dose rates for diatoms are significant (9.7 µGy/h) and comparable to the threshold (10 µGy/h) for the protection of the ecosystems suggested by the literature. In a first attempt of simulating the radiation induced DNA damage on this species, the rate of DNA Double Strand Breaks per day is estimated to 1.11E-04. Our study confirms the significant mutational pressure from natural radioactivity to which microbial biodiversity has been exposed since Earth origin in hydrothermal springs.

Diatom DNA metabarcoding to assess the effect of natural radioactivity in mineral springs on ASV of benthic diatom communities.

Little is still known about the low dose effects of radiation on the microbial communities in the environment. Mineral springs are ecosystems than can be affected by natural radioactivity. These extreme environments are, therefore, observatories for studying the influence of chronic radioactivity on the natural biota. In these ecosystems we find diatoms, unicellular microalgae, playing an essential role in the food chain. The present study aimed to investigate, using DNA metabarcoding, the effect of natural radioactivity in two environmental compartments (i.e. spring sediments and water) on the genetic richness, diversity and structure of diatom communities in 16 mineral springs in the Massif Central, France. Diatom biofilms were collected during October 2019, and a 312 bp region of the chloroplast gene rbcL (coding for the Ribulose Bisphosphate Carboxylase) used as a barcode for taxonomic assignation. A total of 565 amplicon sequence variants (ASV) were found. The dominant ASV were associated with Navicula sanctamargaritae, Gedaniella sp., Planothidium frequentissimum, Navicula veneta, Diploneis vacillans, Amphora copulata, Pinnularia brebissonii, Halamphora coffeaeformis, Gomphonema saprophilum, and Nitzschia vitrea, but some of the ASVs could not be assigned at the species level. Pearson correlation failed to show a correlation between ASV' richness and radioactivity parameters. Non-parametric MANOVA analysis based on ASVs occurrence or abundances revealed that geographical location was the main factor influencing ASVs distribution. Interestingly, 238U was the second factor that explained diatom ASV structure. Among the ASVs in the mineral springs monitored, ASV associated with one of the genetic variants of Planothidium frequentissimum was well represented in the springs and with higher levels of 238U, suggesting its high tolerance to this particular radionuclide. This diatom species may therefore represent a bio-indicator of high natural levels of uranium.

Nickel Retention on Callovo-Oxfordian Clay: Applicability of Existing Adsorption Models for Dilute Systems to Real Compact Rock.

In a waste management context, predicting the mobility of contaminants is essential. A key issue entails assessing the applicability of current knowledge on adsorption processes to natural systems. Such is the focus herein for nickel in interaction with Callovo-Oxfordian (COx) clay rock, a formation selected in France for possible radioactive waste disposal. The challenge is to link predictive modeling results with the experimental data characterizing the behavior of the labile and naturally occurring Ni fraction by implementing a new simple method. Retention studies on compact systems serve to complete this work. Combined electron microprobe and laser ablation high-resolution inductively coupled plasma mass spectrometry data show that natural Ni (∼39 mg kg-1) is homogeneously distributed within the clay matrix, which corresponds to the main reservoir (∼70%). Data interpretation of desorption tests yields an in situ Kd value of ∼80 L kg-1 and a labile Ni amount of ∼5 mg kg-1, that is, ∼13% of the Ni inventory. Predictive modeling explains the sorption data in considering that only weak clay fraction sites take part in the adsorption. The role of the clay matrix in Ni retention is confirmed by analyzing the Ni-spiked compact COx samples, whereby an increase of the Ni content in the clay fraction is observed following the retention experiment.

Predictive factors for lumacaftor/ivacaftor clinical response.

BACKGROUND: Ivacaftor-lumacaftor combination therapy corrects the F508 del-CFTR mutated protein which causes Cystic Fibrosis. The clinical response of the patients treated with the combination therapy is highly variable. This study aimed to determine factors involved in the individual's response to lumacaftor-ivacaftor therapy. METHODS: Sweat test was assessed at baseline and after 6 months of ivacaftor-lumacaftor treatment in 41 homozygous F508del children and young adults. ß-adrenergic peak sweat secretion, nasal potential difference (NPD) and intestinal current measurements (ICM) were performed in patients accepting these tests. Seric level of lumacaftor and ivacaftor were determined and additional CFTR variant were searched. RESULTS: Sweat chloride concentration significantly decreased after treatment, whereas the ß-adrenergic peak sweat response did not vary in 9 patients who underwent these tests. The average level of F508del-CFTR activity rescue reached up to 15% of the normal level in intestinal epithelium, as studied by ICM in 12 patients (p = .03) and 20% of normal in the nasal epithelium in NPD tests performed in 21 patients (NS). There was no significant correlation between these changes and improvements in FEV1 at 6 months. Serum drug levels did not correlate with changes in FEV1, BMI-Zscore or other CFTR activity biomarkers. Additional exonic variants were identified in 4 patients. The F87L-I1027T-F508del-CFTR complex allele abolished the lumacaftor corrector effect. CONCLUSION: This observational study investigates a number of potential factors linked to the clinical response of F508del homozygous patients treated with lumacaftor-ivacaftor combination therapy. Lumacaftor and ivacaftor blood levels are not associated with the clinical response. Additional exonic variants may influence protein correction.

[NUTRITIONAL STATUS ASSESSMENT IN PATIENTS WITH CYSTIC FIBROSIS]. / Prise en charge nutritionnelle de la mucoviscidose.

Prognosis of cystic fibrosis has been largely modified over the past 30 years. Optimization of nutrition is one of the most important contributing factors of this improvement. Nutritional defect result from the conjunction of loss of calories, maldigestion, hypercatabolism and insufficient intake. Pancreatic opotherapy and ADEK vitamin administration is mandatory in pancreatic insufficient patients. Nutritional status must be evaluated at each clinics to detect nutritional defect as early as possible. Nutritional intake must be hypercaloric, normalipidic and adapted to the tastes of the patient. The clinician must be aware of at risk nutritional period: first year of life, puberty, infectious exacerbation, respiratory worsening and diabetes, In neonatal screened babies, recovery of birth weight percentile must be targeted at 6 months, and for the height must be in accordance to genetic height at 2 years. In all cases it is mandatory to treat denutrition by oral supplementation and if necessay enteral nutrition.