Biology subjects

Vignolini, S.

Publications and source records attributed to Vignolini, S..

7 recordsLinked to original sources

bioRxiv2026

Intracellular photonic crystals in photosynthetic sea slugs form via a kidney-mediated biomineralisation pathway

Sea slugs in the Sacoglossa superorder are some of the few animals capable of photosynthesising by isolating and maintaining functional chloroplasts within their body1,2. While this ability allows some species in this superorder, such as Elysia viridis, to appear green, camouflaging themselves within their surroundings3,4, this species is marked by extremely bright, coloured regions. Here, we show that these animals produce a yet undiscovered class of photonic structure consisting of intracellular mixed amorphous CaCO3 and calcite spherical nanoparticles organised in non-closed-packed face-centred cubic (FCC) lattices and photonic glasses5. By mapping the distribution of the cells containing such architectures, we suggest that their colour is linked both to their function and to their biological formation via the animals renal system. Using a combination of different optical methods and cryo-electron microscopy, we reveal that the biomineralisation pathway proceeds through stages of calcium ion concentration in the kidney, transport via internal vessels, and precipitation from a dense liquid-like precursor, culminating in the formation of monodisperse nanoparticles, which are the building blocks of these photonic structures.

biophysics↗

bioRxiv2025

Nudibranch color diversity shares a common origin in guanine photonic structures

Nudibranchs are well known for their bright and diverse color patterns. This coloration is typically a form of aposematism, warning predators against toxic compounds sequestered from their prey and weaponized as a form of defense. Although many of the hues in nudibranchs have pigmentary origin, multilayer structures composed of guanine nano-platelets have been suggested as the source of color enhancement in the nudibranch Flabellina iodenea. Here, using a combination of white light and Raman microspectroscopy techniques, we report that such guanine-based multilayer structures are a widespread mechanism to create angular-independent structural color across the dorid and aeolid groups. Additionally, by using cryo-FIB tomography, we were able to access the complex 3D organization of the guanine nano-platelets responsible for the strong blue coloration of Chromodoris annae. We propose that the multilayer organization of guanine platelets with varying orientations across the tissue offers a particularly effective strategy for producing diverse optical effects. In this configuration, hue is mainly governed by interlayer spacing, while the angular dependence of color can be tuned through the degree of local order, allowing a single structural motif to generate a broad palette of optical appearances. Significance statementNudibranchs are an extraordinarily diverse group of marine animals, renowned for their dazzling range of colors and striking patterns. Whilst their pigmentary coloration is well understood, so far, structural coloration, obtained only by nanostructures, has only been reported in the nudibranch Flabellina iodenea. In this work, we present a comparative analysis of structural coloration across nudibranch species from both benthic and coral reef environments, and we show that guanine-based nano-structures are a common motif responsible for a wide range of colors, spanning the dorid and aeolid groups. We foresee that the 3D imaging conducted here may serve as inspiration for bio-photonics studies in other marine organisms, and that the structures themselves could serve as inspiration for bio-inspired materials.

biophysics↗

bioRxiv2025

Cultivating Future Materials: Artificial Symbiosis for Bulk Production of Bacterial Cellulose Composites

Symbiotic relationships between micro-organisms are the basis of all global ecosystems. Here we extrapolate this concept for novel material fabrication by creating artificial symbiotic relationships between species that are usually not grown synergistically in nature. Specifically, we combine the cellulose-producing bacterium Komagataeibacter hansenii and the green microalga Chlamydomonas reinhardtii to obtain bulk growth of bacterial cellulose. Usually, bacterial cellulose is produced as floating pellicles at the air-liquid interface of the growing media, because free oxygen, together with the nutrients in the culture medium, is required for the bacteria to synthesise the cellulose fibres. In the co-culture, bacterial cellulose production can be achieved in bulk beyond the restriction of the liquid/air interface as the motile microalgae act as oxygen-generating sites within the culture medium. In exchange, the highly porous and mechanically robust scaffold provided by the cellulose allows the algal community to form a healthy biofilm, which can reach several centimetres thick. We demonstrate that our growing platform allows the simultaneous production of bulk bacterial cellulose in static incubation conditions, taking up an arbitrary and yet tunable 3D shape, dependent on the geometry of the culture vessel and with a relatively high biomass output.

microbiology↗

bioRxiv2025

Deletion of the moe A gene in Flavobacterium IR1 drives structural color shift from green to blue and alters polysaccharide metabolism

Structural color (SC), generated by light interacting with nanostructured materials, are responsible for the brightest and most vivid coloration in nature. Despite being widespread within the tree of life, there is little knowledge of the genes involved. Partial exceptions are some colonies of Flavobacteriia in which genes involved in a number of pathways, including gliding motility and polysaccharide metabolism, have been linked to SC. A previous genomic analysis of SC and non-SC bacteria suggested that the pterin pathway is involved in the organization of bacteria to form SC. Thus here, we focus on the moeA molybdopterin molybdenum transferase. When this gene was deleted from Flavobacterium IR1, the knock- out mutant showed a strong blue shift in SC of the colony, different from the green SC of the wild-type. The moeA mutant showed a particularly strong blue shift when grown on kappa- carrageenan and was upregulated for starch degradation. To further analyze the molecular changes, proteomic analysis was performed, showing the upregulation of various polysaccharide utilization loci, which supported the link between moeA and polysaccharide metabolism in SC. Overall, we demonstrated that single-gene mutations could change the optical properties of bacterial SC, which is unprecedented when compared to multicellular organisms where structural color is the result of several genes and can not yet be addressed genetically.

microbiology↗

bioRxiv2023

Light management by algal aggregates in living photosynthetic hydrogels.

Rapid progress in algal biotechnology has triggered a growing interest in hydrogel-encapsulated microalgal cultivation, especially for the engineering of functional photosynthetic materials and biomass production. An overlooked characteristic of gel-encapsulated cultures is the emergence of cell aggregates, which are the result of the mechanical confinement of the cells. Such aggregates have a dramatic effect on the light management of gel-encapsulated photobioreactors and hence strongly affect the photosynthetic outcome. In order to evaluate such an effect, we experimentally studied the optical response of hydrogels containing algal aggregates and developed optical simulations to study the resultant light intensity profiles. The simulations are validated experimentally via transmittance measurements using an integrating sphere and aggregate volume analysis with confocal microscopy. Specifically, the heterogeneous distribution of cell aggregates in a gel matrix can increase light penetration while alleviating photoinhibition compared to a flat biofilm. Finally, we demonstrate that light harvesting efficiency can be further enhanced with the introduction of scattering particles within the hydrogel matrix, leading to a four-fold increase in biomass growth. Our study, therefore, highlights a new strategy for the design of spatially efficient photosynthetic living materials that have important implications for the engineering of future algal cultivation systems. Significance StatementThe ability to cultivate microalgae at scale efficiently would allow more sustainable production of food and food additives. However, efficient growth of microalgae requires optimised light conditions, which are usually challenging to obtain using biofilm cultivations mode: as the outer layer of cells are necessarily more exposed to incoming light than the inner layer, posing the problem of photoinhibition on the outer cells receiving too much light, and shading the ones below. Here we study both experimentally and numerically, how microalgae aggregates growing in the confinement of a hydrogel can provide an improved light distribution and therefore biomass growth is maximised. This study proposes new strategies on how to engineer future photobioreactors.

plant biology↗

bioRxiv2021

Synthetic algal-bacteria consortia for space-efficient microalgal growth in a simple hydrogel system

Photosynthetic microalgae are an attractive source of food, fuel or nutraceuticals, but commercial production of microalgae is limited by low spatial efficiency. In the present study, we developed a simple photosynthetic hydrogel system that cultivates the green microalga, Marinichlorella kaistiae KAS603, together with a novel strain of the bacteria Erythrobacter sp.. We tested the performance of the co-culture in the hydrogel using a combination of chlorophyll-a fluorimetry, microsensing and bio-optical measurements. Our results showed that growth rates in algal-bacterial hydrogels were about 3-fold enhanced compared to hydrogels with algae alone. Chlorophyll-a fluorimetry based light curves found that electron transport rates were enhanced about 20% for algal-bacterial hydrogels compared to algal hydrogels for intermediate irradiance levels. We also show that the living hydrogel is stable under different environmental conditions and when exposed to natural seawater. Our study provides a potential bio-inspired solution for problems that limit the space-efficient cultivation of microalgae for biotechnological applications.

microbiology↗

bioRxiv2019

Bionic 3D printed corals

Symbiotic corals have evolved as a highly optimised photon augmentation system leading to space-efficient microalgal growth and photosynthetic quantum efficiencies that approach theoretical limits1-3. Corals are characterized by an elastic animal tissue hosting microalgae and a light scattering calcium carbonate skeleton that maximizes light delivery towards otherwise shaded algal-containing tissues4,5. Rapid light attenuation due to algal self-shading is a key limiting factor for the upscaling of microalgal cultivation6,7. Coral-inspired light management systems could overcome this limitation and facilitate scalable bioenergy and bioproduct generation8,9. Here, we developed 3D printed bionic corals capable of growing various types of microalgae with cell densities approaching 109 cells mL-1, up to 100 times greater than in liquid culture. The hybrid photosynthetic biomaterials are produced with a new 3D bioprinting platform which mimics morphological features of living coral tissue and the underlying skeleton with micron resolution, including their optical and mechanical properties. The programmable synthetic microenvironment thus allows for replicating both structural and functional traits of the coral-algal symbiosis. Our work defines a new class of bionic materials capable of interacting with living organisms, that can be exploited for the design of next generation photobioreactors7 and disruptive approaches for coral reef conservation10.

bioengineering↗