Autotrophic and heterotrophic acquisition of carbon and nitrogen by a mixotrophic chrysophyte established through stable isotope analysis

Collectively, phagotrophic algae (mixotrophs) form a functional continuum of nutritional modes between autotrophy and heterotrophy, but the specific physiological benefits of mixotrophic nutrition differ among taxa. Ochromonas spp. are ubiquitous chrysophytes that exhibit high nutritional flexibility, although most species generally fall towards the heterotrophic end of the mixotrophy spectrum. We assessed the sources of carbon and nitrogen in Ochromonas sp. strain BG-1 growing mixotrophically via short-term stable isotope probing. An axenic culture was grown in the presence of either heat-killed bacteria enriched with ^(15)N and ^(13)C, or unlabeled heat-killed bacteria and labeled inorganic substrates (^(13)C-bicarbonate and ^(15)N-ammonium). The alga exhibited high growth rates (up to 2 divisions per day) only until heat-killed bacteria were depleted. NanoSIMS and bulk IRMS isotope analyses revealed that Ochromonas obtained 84–99% of its carbon and 88–95% of its nitrogen from consumed bacteria. The chrysophyte assimilated inorganic ^(13)C-carbon and ^(15)N-nitrogen when bacterial abundances were very low, but autotrophic (photosynthetic) activity was insufficient to support net population growth of the alga. Our use of nanoSIMS represents its first application towards the study of a mixotrophic alga, enabling a better understanding and quantitative assessment of carbon and nutrient acquisition by this species

Towards eco-friendly crop protection: natural deep eutectic solvents and defensive secondary metabolites

Plant science

HydroGEV: Extracellular Vesicle-Laden Hydrogel for Wound Healing Applications

Chronic wounds contribute a substantial social and economic burden on the healthcare system. The global cost of wound treatment was about $19.8 Billion USD in 2019. Healing of chronic wounds takes typically more than 3 months. Current treatments are ineffective and do not always promote wound closure, which requires the activation of multiple cell types. Extracellular vesicles (EVs) contain multiple biomolecules that influence surrounding cells and thus have large capacity to promote tissue repair. To harness the chemoattractant properties of EVs, we developed an extracellular vesicle-laden hydrogel (HydroGEV) with optimized stiffness to promote functional tissue repair, since both mechanical and biological factors influence cell growth and subsequent tissue repair. EVs were isolated and purified from placental stem cells, characterized and incorporated into a gelatin-based hydrogel (GHPA) with different relative stiff-nesses (low, medium and high) determined by crosslinking density. The EVs were found to increase the migration capability of cells in a migration assay, confirming their strong chemoattractant properties and supporting their application for cell recruitment in wound healing. When incorporated into GHPA hydrogels, the EVs effectively improved cell attachment regardless of the stiffness of the hydrogels. Importantly, we demonstrated that by optimizing hydrogel stiffness it was possible to achieve higher cell proliferation and more phenotypic morphology. These promising results support the potential of HydroGEV as a better therapeutic option for patients with acute or chronic wounds

Manipulation of Leaf Litter Stoichiometry

International audienc