Biology subjects

Svagan, A. J.

Publications and source records attributed to Svagan, A. J..

3 recordsLinked to original sources

bioRxiv2026

Chemistry and Structure of Birch Bark Support Passive Radiative Cooling

White-barked birches extend to the northern limit of tree growth, and their bark is known to reduce solar damage during winter and early-spring by limiting solar heating and the incidence of harmful freeze-thaw events. The physical basis for this protection, however, has remained unclear. Here, we show that extracted betulin, the dominant triterpenoid responsible for the bark's whiteness, and Himalayan birch bark, both exhibit passive radiative cooling. Under low solar irradiance, bark and betulin-pellets reach temperatures below that of a shaded reference, and pellets cool more than bark. The cooling arises from high solar reflectance, which suppresses solar heating, and substantial mid-infrared emission, which drives radiative heat loss toward outer space. These findings help explain how bark-whiteness may contribute to protecting birch trees from solar-induced thermal stress.

plant biology↗

bioRxiv2026

Carbon substrate type shapes spatial self-organization in a multi-species biofilm community

Spatial organization is a defining feature of multispecies biofilms and critically influences microbial interactions and emergent community properties. However, understanding and manipulating how microbes assemble into spatially structured biofilms remains challenging because most experimental frameworks emphasize species composition and pairwise interactions, while often overlooking the spatial constraints on biofilms imposed by the environment. In this study, we focus on how carbon substrate type, distinguishing between diffusible sugars and polymeric substrates, affects biofilm self-organization in a four-member synthetic bacterial community (SynCom). Across all tested conditions, the SynCom consistently formed more biofilm biomass than any of its subsets, indicating a robust synergistic phenotype. Using chemically defined, 3D-printed hydrogel substrates with consistent physical properties, we varied carbon source composition to identify its impact on biofilm assembly. Microscopic imaging showed that carbon substrate type strongly influenced biofilm self-organization with diffusible simple carbon substrates yielding relatively intermixed communities, whereas polymer-rich carbon substrates promoted a highly structured biofilm organization characterized by the dominance and peripheral localization of polymer-degrading species. Bioinformatic analyses of carbohydrate-active enzymes (CAZymes) annotation and genome-scale metabolic modeling suggested that metabolite exchange networks in the SynCom may drive more complex metabolic interactions beyond the commonly observed degrader-exploiter-scavenger relationship within planktonic microbial communities. Together, our findings demonstrate carbon substrate type as an important ecological determinant of biofilm self-organization, highlighting the need to integrate environmental factors alongside species composition and metabolic potential to fully understand and manipulate natural and engineered multispecies biofilms.

microbiology↗

bioRxiv2025

Synthetic pectin-cellulose nanofiber capsule provides minimal model capturing mechanics of a regenerating plant cell wall

Plant primary cell walls are dynamic supramolecular assemblies composed of layered cellulose, hemicellulose and pectin, progressively built through synthesis and secretion. However, the specific architectural features and structural components sufficient to endow the mechanical properties of the wall remain unclear. Here, we construct a minimal synthetic spherical shell and compare its structural and mechanical properties to those of a plant single-cell system. To eliminate complexities from intercellular connectivity and developmental history, we exploit the ability of plant protoplasts to regenerate cell walls de novo. Compression tests of regenerating protoplasts between parallel plates reveal that wall stiffness increases with wall thickening over time. Despite differences in assembly pathways, architecture, and composition, the synthetic shell exhibits a similar thickness-dependent modulus and similar material stiffness. The synthetic shell, composed of pectin and cellulose layers, mirrors the mechanical behavior of regenerating primary cell walls, suggesting that these components are sufficient to confer key viscoelastic properties in the limit of small deformations. Given the complexity of natural plant cell walls, the synthetic analogue offers a controllable platform to dissect the mechanical contributions of individual wall components.

plant biology↗