Assessment of the Potential Role of Streptomyces in Cave Moonmilk Formation

Moonmilk is a karstic speleothem mainly composed of fine calcium carbonate crystals (CaCO3) with different textures ranging from pasty to hard, in which the contribution of biotic rock-building processes is presumed to involve indigenous microorganisms. The real microbial input in the genesis of moonmilk is difficult to assess leading to controversial hypotheses explaining the origins and the mechanisms (biotic vs. abiotic) involved. In this work, we undertook a comprehensive approach in order to assess the potential role of filamentous bacteria, particularly a collection of moonmilk-originating Streptomyces, in the genesis of this speleothem. Scanning electron microscopy (SEM) confirmed that indigenous filamentous bacteria could indeed participate in moonmilk development by serving as nucleation sites for CaCO3 deposition. The metabolic activities involved in CaCO3 transformation were furthermore assessed in vitro among the collection of moonmilk Streptomyces, which revealed that peptides/amino acids ammonification, and to a lesser extend ureolysis, could be privileged metabolic pathways participating in carbonate precipitation by increasing the pH of the bacterial environment. Additionally, in silico search for the genes involved in biomineralization processes including ureolysis, dissimilatory nitrate reduction to ammonia, active calcium ion transport, and reversible hydration of CO2 allowed to identify genetic predispositions for carbonate precipitation in Streptomyces. Finally, their biomineralization abilities were confirmed by environmental SEM, which allowed to visualize the formation of abundant mineral deposits under laboratory conditions. Overall, our study provides novel evidences that filamentous Actinobacteria could be key protagonists in the genesis of moonmilk through a wide spectrum of biomineralization processes

Enantioselective Access to <i>Lobelia</i> Alkaloids

Enantioselective Access to Lobelia Alkaloid

Moult-related changes in the integument, midgut, and digestive gland in the freshwater amphipod gammarus pulex

On the basis of macroscopic aspects (body and eye colour, lipid droplets), it was possible to sort specimens of Gammarus pulex (Linnaeus, 1758) into five categories that correspond to moult periods and stages (A, B, C, D1 and D2) based on integument features (tergite cuticle stiffness, layers and thickness). These stages also correspond to changes in digestive tract histology (gut content, cell ultrastructure, and lipid storage). With reference to the pereion tergite integument, this makes it possible to standardize moulting stage terminology and criteria with those applied to decapods while validating a quick, simple, moult-staging method that avoids injury and informs us about the physiology of the whole organism. The moult cycle was very short (about 12-15 days), with a "virtual," practically non-existent, anecdysis or "integument resting period" between post-ecdysis and pre-ecdysis. The pore canals previously known to be "open to the outside" appeared closed at early post-ecdysis by a lipid-rich fillng material that could be responsible for the cuticular waterproofing barrier allowing mineral deposition. In the digestive tract, the main structural changes were late post-ecdysial loss of midgut cells and digestive gland B-cells (probably by extrusion) when restarting the feeding cycle. Pre-ecdysial increase and post-ecdysial decrease in storage lipids are also obvious. We present a quick moult-staging method to sort a great number of G. pulex for physiological or toxicological assays investigating how animals at specific periods of their moult cycle respond to both natural and anthropogenic environmental changes

Anticiper pour mieux planifier – Éditorial

En réunissant la communauté professionnelle de l’eau et de l’agriculture, le colloque « Anticiper pour mieux planifier : quelle demande en eau pour quelle agriculture demain ? » a permis de faire le point sur les méthodes mobilisables et les actions engagées pour améliorer l’anticipation de la demande en eau agricole à l’horizon 2050, tout en soulevant des questions cruciales : sur quelles données de base se fonde la gestion de la ressource en eau ? Quel est le degré de fiabilité de ces données, et que nous disent-elles sur la situation et les tensions actuelles et à venir ? Cet événement a été organisé le 28 septembre 2023 par la Chaire partenariale Eau, Agriculture et Changement Climatique, le réseau INRAE « Systèmes agricoles et Eau » et le pôle Aqua-Valley. L'adaptation au changement climatique et la promotion de pratiques agricoles durables, minimisant les besoins en eau d'irrigation, ont été au cœur des échanges et constituent le cœur de ce numéro spécial

NI956/QGC006, a Potent Orally Active, Brain-Penetrating Aminopeptidase A Inhibitor for Treating Hypertension

Brain renin-angiotensin system hyperactivity has been implicated in the development and maintenance of hypertension. We have shown that aminopeptidase A is involved in the formation of brain angiotensin III, which exerts tonic stimulatory control over blood pressure in hypertensive deoxycorticosterone acetate-salt rats and spontaneously hypertensive rats. We have also shown that injection of the specific and selective aminopeptidase A inhibitor, (3S)-3-amino-4-sulfanyl-butane-1-sulfonic acid (EC33), by central route or its prodrug, RB150/firibastat, by oral route inhibited brain aminopeptidase A activity and blocked the formation of brain angiotensin III, normalizing blood pressure in hypertensive rats. These findings identified brain aminopeptidase A as a potential new therapeutic target for hypertension. We report here the development of a new aminopeptidase A inhibitor prodrug, NI956/QGC006, obtained by the disulfide bridge-mediated dimerization of NI929. NI929 is 10× more efficient than EC33 at inhibiting recombinant mouse aminopeptidase A activity in vitro. After oral administration at a dose of 4 mg/kg in conscious deoxycorticosterone acetate-salt rats, NI956/QGC006 normalized brain aminopeptidase A activity and induced a marked decrease in blood pressure of −44±13 mm Hg 4 hours after treatment ( P&lt; 0.001), sustained over 10 hours (−21±12 mm Hg; P&lt; 0.05). Moreover, NI956/QGC006 decreased plasma arginine-vasopressin levels, and increased diuresis and natriuresis, that may participate to the blood pressure decrease. Finally, NI956/QGC006 did not affect plasma sodium and potassium concentrations. This study shows that NI956/QGC006 is a best-in-class central-acting aminopeptidase A inhibitor prodrug. Our results support the development of hypertension treatments targeting brain aminopeptidase A. </jats:p