Liquid-liquid phase separation promotes animal desiccation tolerance.

Proteinaceous liquid-liquid phase separation (LLPS) occurs when a polypeptide coalesces into a dense phase to form a liquid droplet (i.e., condensate) in aqueous solution. In vivo, functional protein-based condensates are often referred to as membraneless organelles (MLOs), which have roles in cellular processes ranging from stress responses to regulation of gene expression. Late embryogenesis abundant (LEA) proteins containing seed maturation protein domains (SMP; PF04927) have been linked to storage tolerance of orthodox seeds. The mechanism by which anhydrobiotic longevity is improved is unknown. Interestingly, the brine shrimp Artemia franciscana is the only animal known to express such a protein (AfrLEA6) in its anhydrobiotic embryos. Ectopic expression of AfrLEA6 (AWM11684) in insect cells improves their desiccation tolerance and a fraction of the protein is sequestered into MLOs, while aqueous AfrLEA6 raises the viscosity of the cytoplasm. LLPS of AfrLEA6 is driven by the SMP domain, while the size of formed MLOs is regulated by a domain predicted to engage in protein binding. AfrLEA6 condensates formed in vitro selectively incorporate target proteins based on their surface charge, while cytoplasmic MLOs formed in AfrLEA6-transfected insect cells behave like stress granules. We suggest that AfrLEA6 promotes desiccation tolerance by engaging in two distinct molecular mechanisms: by raising cytoplasmic viscosity at even modest levels of water loss to promote cell integrity during drying and by forming condensates that may act as protective compartments for desiccation-sensitive proteins. Identifying and understanding the molecular mechanisms that govern anhydrobiosis will lead to significant advancements in preserving biological samples.

Reliability of antioxidant potential and in vivo compatibility with extremophilic actinobacterial-mediated magnesium oxide nanoparticle synthesis.

Owing to the hazards of chemical and physical syntheses of magnesium oxide nanoparticles (MgO NPs), an eco-friendly, high-yield, and promising biological method is highly desirable for biomedical applications. Hence, in this study, an extremophilic actinobacterial population (SA8 and SA10) from Salem magnesite mining soil was used as precursors for MgO NP synthesis. The prepared nanoparticles were subjected to X-ray diffraction study and showed face-centred cubic structure with an average particle size of 18-24 nm. Among all, high yield was obtained in SA10 actinobacteria-mediated synthesis of MgO NPs (480 mg/100 mL). In addition, the prepared MgO NPs (10 mg/well) showed 15-17 mm zone of inhibition against bacterial pathogens, especially bigger zones around SA10. The 64.5% antioxidant activity and nonsignificant toxicity of actinobacteria-synthesized MgO NPs in MG-63 cell lines at 100 µg/mL and nonsignificant in vivo toxicity in zebrafish at 0.1 mg/mL were remarkable. In addition, this is the first study to focus on MgO NP synthesis using extremophilic actinobacteria collected from Salem magnesite mining soil for high yield (115 mg/100 mL), reliable with potential antioxidant, and in vitro and in vivo compatibility. These results provided useful information for advanced research and mass production of NP for biomedical applications.