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Isolation of the adhesive material from C. australis (a–c) and A. coffeaeformis (d–f). All images show surfaces after staining with the dye ‘Stains-All’. (a, d) Surfaces with attached cells after 16 h cultivation. Some cells are labeled with asterisks. Arrows indicate adhesive trails. (b, e) Surfaces after water spraying. (c, f) Surfaces after scraping. Scale bar = 20 μm.
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Many aquatic organisms are able to colonize surfaces through the secretion of underwater adhesives. Diatoms are unicellular algae that have the capability to colonize any natural and man-made submerged surfaces. There is great technological interest in both mimicking and preventing diatom adhesion, yet the biomolecules responsible have so far remai...
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... allow for the deposition of diatom adhesive on sur- faces, aggregate-free cell suspensions of C. australis and A. coffeaeformis were seeded onto polystyrene Petri dishes and cultivated overnight. During this time the cells adhered to the surface as a monolayer, and deposited trails consisting of the adhesive material (Figure 1a, d). Subsequently, removal of the cells from the surface was accomplished by spraying controlled jet pulses of water (delivered by a 'water flosser' apparatus) over the entire Petri dish surface. ...
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... of A. coffeaeformis cells required a higher water pressure than removal of C. australis, which is consistent with the previously reported higher adhesion strength of A. coffeaeformis ( Holland et al. 2004). The water spraying removed the cells efficiently from the Petri dish surface, but not the adhesive trails, as was demonstrated by light microscopy after staining the trails with the dye 'Stains-All' (Campbell et al. 1983) before (Figure 1a, d) and after (Figure 1b, e) water spraying. Following removal of the cells, the adhesive material was recovered by scraping it off the Petri dish surface using a cell lifter. ...
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... of A. coffeaeformis cells required a higher water pressure than removal of C. australis, which is consistent with the previously reported higher adhesion strength of A. coffeaeformis ( Holland et al. 2004). The water spraying removed the cells efficiently from the Petri dish surface, but not the adhesive trails, as was demonstrated by light microscopy after staining the trails with the dye 'Stains-All' (Campbell et al. 1983) before (Figure 1a, d) and after (Figure 1b, e) water spraying. Following removal of the cells, the adhesive material was recovered by scraping it off the Petri dish surface using a cell lifter. ...
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... removal of the cells, the adhesive material was recovered by scraping it off the Petri dish surface using a cell lifter. After scraping, staining with 'Stains-All' indicated essentially complete removal of the adhesive material from the sur- face (Figure 1c, f). The scraped-off adhesive material was lyophilized to dryness yielding 24.6 ± 4.5 μg (from A. coffeaeformis) and 34.2 ± 6.1 μg (from C. australis) of solid material per 100 cm 2 of dish surface. ...
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... other signal groups could be due to the presence of both proteins and polysaccharides. By comparing the intensity of signal group 4 with the total signal in each spectrum ( Figure S1) and assuming exclusively hexoses as polysaccharide constituents it was estimated that ≥ 70% of the organic components of the isolated adhesive material from A. coffeaeformis and C. australis are composed of polysaccharide. The other organic components (< 30% of the total material) are probably proteins. ...
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Citations
... This procedure was adopted from. [11,71] A total of 120 μL drops of stains were added to each sample and air-dried in the dark for 15 min. After drying, the remaining dies were removed, and the sample was imaged under a VK-X1000 profilometer (Keyence Corporation, United States). ...
This work proposes an octopus‐inspired smart skin for fouling release. The skin consists of twisted spiral artificial muscles (TSAMs) embedded between two layers of elastomer. Upon electro‐thermal actuation, TSAMs undergo vertical displacement (similarly to octopus’ papillae dermal muscles) and mechanically deform the top layer of the skin where the biofilm is attached. The release is achieved by generating a critical strain on the skin's top layer. In this paper, a physics‐based mechanical model is proposed to describe the fouling release mechanism of the smart skin. The model relates the critical strain to the mechanical properties of the biofilm, as well as the mechanical and electro‐thermal properties of the TSAMs. The model is experimentally validated, and a robust controller is implemented to achieve the desired critical strain and then perform release for two different types of biofilms: bacterial‐based Escherichia coli and diatom‐based Amphora coffeaeformis.
... The raphe acts as a channel for the secretion of a complex mixture of proteins and glycoproteins [17][18][19][20][21] known collectively as extracellular polymeric substances (EPS). Motility can be blocked by an antibody to EPS [17] and by actomyosin inhibitors [22,23], suggesting that both systems play essential roles. ...
Diatoms are ancestrally photosynthetic microalgae. However, some underwent a major evolutionary transition, losing photosynthesis to become obligate heterotrophs. The molecular and physiological basis for this transition is unclear. Here, we isolate and characterize new strains of non-photosynthetic diatoms from the coastal waters of Singapore. These diatoms occupy diverse ecological niches and display glucose-mediated catabolite repression, a classical feature of bacterial and fungal heterotrophs. Live-cell imaging reveals deposition of secreted extracellular polymeric substance (EPS). Diatoms moving on pre-existing EPS trails (runners) move faster than those laying new trails (blazers). This leads to cell-to-cell coupling where runners can push blazers to make them move faster. Calibrated micropipettes measure substantial single-cell pushing forces, which are consistent with high-order myosin motor cooperativity. Collisions that impede forward motion induce reversal, revealing navigation-related force sensing. Together, these data identify aspects of metabolism and motility that are likely to promote and underpin diatom heterotrophy.
... As current synthetic adhesives are normally undermined by moisture (8,27), it is conceptually unique to turn water into a helper. The design of water-involved and water-triggered underwater adhesion helps deeply remove interfacial water and promotes cohesion, allowing for rapid and robust wet adhesion on broad choices of solid substrates in a process entirely immersed in water. ...
In nearly all cases of underwater adhesion, water molecules typically act as a destroyer. Thus, removing interfacial water from the substrate surfaces is essential for forming super-strong underwater adhesion. However, current methods mainly rely on physical means to dislodge interfacial water, such as absorption, hydrophobic repulsion, or extrusion, which are inefficient in removing obstinate hydrated water at contact interface, resulting in poor adhesion. Herein, we present a unique means of reversing the role of water to assist in realizing a self-strengthening liquid underwater adhesive (SLU-adhesive) that can effectively remove water at contact interface. This is achieved through multiscale physical-chemical coupling methods across millimeter to molecular levels and self-adaptive strengthening of the cohesion during underwater operations. As a result, strong adhesion over 1,600 kPa (compared to ~100 to 1,000 kPa in current state of the art) can be achieved on various materials, including inorganic metal and organic plastic materials, without preloading in different environments such as pure water, a wide range of pH solutions (pH = 3 to 11), and seawater. Intriguingly, SLU-adhesive/photothermal nanoparticles (carbon nanotubes) hybrid materials can significantly reduce the time required for complete curing from 24 h to 40 min using near-infrared laser radiation due to unique thermal-response of the chemical reaction rate. The excellent adhesion property and self-adaptive adhesion procedure allow SLU-adhesive materials to demonstrate great potential for broad applications in underwater sand stabilization, underwater repair, and even adhesion failure detection as a self-reporting adhesive. This concept of "water helper" has potential to advance underwater adhesion and manufacturing strategies.
... hydrophobic, and electrostatic interaction. [32] Proteins containing DOPA, which mediate underwater adhesion of mussels, are absent. The presence of both proteins and polysaccharides of diatoms acts synergistically in displacing water, ions, and lowaffinity ligands from the substratum surface, thus allowing the protein to bind noncovalently yet strongly to the surface using polyvalent interactions and hydrogen bonding and "curing" with time. ...
Adhesives with strong underwater adhesion performance are urgently needed in diverse areas. However, designing adhesives with long‐term stability to diverse materials underwater in a facile way is challenging. Here, inspired by aquatic diatoms, a series of novel biomimetic universal adhesives is reported that shows tunable performance with robust and long‐lasting stable underwater adhesion to various substrates, including wet biological tissues. The versatile and robust wet‐contact adhesives are pre‐polymerized by N‐[tris(hydroxymethyl)methyl]acrylamide, n‐butyl acrylate, and methylacrylic acid in dimethyl sulfoxide and spontaneously coacervated in water triggered by solvent exchange. The synergistic interaction between hydrogen bonding and hydrophobic interaction allows the hydrogels with instant and strong adhesion to various substrate surfaces. The slowly formed covalent bonds enhance cohesion and adhesion strength in hours. The spatial and timescale‐dependent adhesion mechanism endows the adhesives with strong and long‐lasting stable underwater adhesion to be coupled with fault‐tolerant convenient surgical operations.
... The molecular mechanisms enabling the production of these substances are essential to the ecology of first colonizers in a changing climate. Diatoms adhere through a material composed of both proteins and carbohydrates, secreted by the raphe [80]. It is noteworthy that the extreme events of global changes, such as global warming and ocean acidification, affect the molecular pathways involved in the anchoring mechanisms to modify them, with negative consequences for the control of encrusting organisms. ...
The successions of benthic communities over time are strongly influenced by the first colonizers, because surface associations are facilitated by modifications to the adhesive properties promoted by primary colonizers, such as bacteria, protozoans, diatoms, algal propagules, spores, and invertebrate larvae. Bacteria are often the first colonizers on marine submerged surfaces, both organic (e.g., algae, seagrasses and invertebrates) and inorganic. However, they are promptly followed by diatoms and other microorganisms. Consequently, diatoms may represent key elements in the determination of the colonization patterns, although the development of epiphytic communities is a dynamic process influenced by several factors, including nutrient availability, the ability to synthesize and secrete extracellular material, the competition among species and the influence of grazers on individual colonizers. The process may be drastically impacted by global warming and ocean acidification due to the increasing atmospheric levels of CO2. The impact of such global stressors on benthic ecosystems, especially on the primary microphytobenthic assemblages, is still poorly investigated, and may have deleterious consequences for the benthic successions. In this review, we analyze the adhesion patterns of marine microorganisms according to their surface features and the effects of global changes on critical pioneer colonizers, such as the benthic diatoms. The results are remarkable, as they highlight emergent concerns in ecosystem conservation and the prediction of benthic communities.
... The raphe acts as a channel for secretion of a complex mixture of proteins and glycoproteins [17][18][19][20] known collectively as extracellular polymeric substances (EPS). Motility can be blocked by an antibody to EPS 17 and actin inhibitors 21 , suggesting that both play essential roles. ...
Diatoms are ancestrally photosynthetic microalgae. However, some underwent a major evolutionary transition, losing photosynthesis to become obligate heterotrophs. The molecular and physiological basis for this transition is unclear. Here, we isolate and characterize new strains of non-photosynthetic diatoms from the coastal waters of Singapore. These diatoms occupy diverse ecological niches and display glucose-mediated catabolite repression, a classical feature of bacterial and fungal heterotrophs. Live-cell imaging reveals deposition of secreted extracellular polymeric substance (EPS). Diatoms moving on pre-existing EPS trails (runners) move faster than those laying new trails (blazers). This leads to cell-to-cell coupling where runners can push blazers to make them move faster. Collisions that impede forward motion induce reversal, revealing navigation-related force sensing. Calibrated micropipettes measure substantial single cell pushing forces, which are consistent with high-order myosin cooperativity. Together, these data identify aspects of metabolism and motility that are likely to promote diatom-specific foraging and feeding strategies, underpinning the transition to free-living heterotrophy.
... 58 Some monosaccharides such as fucose and rhamnose appear to be closely involved in the adhesion of diatoms and biofilms. 59,60 The EPS production rates and monosaccharide compositions in diatoms differ according to the growth phase and physiological status of the cells. EPSs with increasing cellular stickiness are often associated with nutrient depletion. ...
Marine diatoms are currently facing increasing threats from microplastic (MP) pollution that is intertwined with the disturbed nutrient stoichiometry in seawater. The effects of nutrient imbalances such as silicon (Si) limitation on the interactions between diatoms and MPs remain poorly understood. In contrast to previous studies which mainly focused on MP toxicity, this study emphasizes how Si availability affects nano-scale interactions between pristine polystyrene MPs and diatom surfaces. Results showed that Si-starved cells were less tolerant to MP toxicity than the Si-enriched counterparts. Si limitation significantly changed the configuration and chemical composition of the perforated frustules, forming less negatively charged, more adhesive, and mechanically weaker cells. All of these changes facilitated the adsorption and hetero-aggregation between the diatom cells and MPs and compromised the diatoms' resistance to MP attack. Our study provides novel insights into the effects of pristine MPs in the marine environment under the context of dynamic nutrient conditions.
... The growth media was then removed from the top of the samples, and the samples were taken out of the beakers. One control sample was rinsed with sterilized DI water and then stained with an optical stain, Stains-All (Sigma-Aldrich, USA) at a concentration of 1 mg mL -1 in formamide (Fisher Scientific, USA) according to the procedure detailed in ref. [63]. 6-8 20 µL drops of Stains-All were added to the sample. ...
The buildup of marine organisms on submerged surfaces, known as biofouling, poses a major threat to the maritime industry. Biofouling on seafaring vessels increases hydrodynamic drag, fuel consumption, and leads to the spread of invasive species. Despite considerable research, a cost‐effective and environmentally friendly strategy for preventing biofouling remains elusive. Silicone‐based fouling release coatings (FRCs) that rely on hydrodynamic shear forces to remove attached biofilms have recently been proposed as a non‐toxic solution for biofouling. However, FRCs are susceptible to fouling in still water or near‐still water conditions. In this study, a smart skin bioinspired by the shape‐changing behavior of octopi for removing biofilms in near‐still water conditions is proposed. Active deformation of the smart skin powered by twisted spiral artificial muscles (TSAMs) leads to the detachment of biofilms. The efficacy of the smart skin is evaluated in both a laboratory setting and a field environment. A maximum of 87% of a laboratory grown and 79% of a heterogeneous field biofilm is detached by the active motion of the skin surface. The results indicate that the actively deformed smart skins bioinspired by octopi are a promising candidate for removing marine biofilms in still or near‐still water environments.
... 2 × 10 6 amphora cells per mL in sterile filtered seawater were prepared from a continuous culture. [80,81] The pre-immersed coatings were incubated in diatom solution for 60 min on an orbital shaker at 65 rpm. Next, the attached diatoms were fixed by applying 2.5 vol % glutaraldehyde solution for 10 min. ...
The three dominating polyzwitterion families, polyphosphatidylcholines, polycarboxybetaines, and polysulfobetaines, all of which provide high fouling resistance, have been complemented by a fourth one recently, the so‐called polysulfabetaines that combine ammonium with sulfate moieties. To elucidate the relationship between their structure and antifouling potential, coatings of a set of systematically varied poly(sulfabetaine methacrylate)s are investigated. In particular, the effects of the spacer groups, either separating the zwitterionic units from the polymer backbone, or the cationic from the anionic charges, are explored, studying the resistance against non‐specific protein adsorption and the accumulation of single species of marine biofouling organisms. All polysulfabetaines are at least as effective, or even more potent than the structurally closely related standard poly(sulfobetaine methacrylate). Their resistance against proteins and fouling organisms can be tuned via the betaine‐to‐backbone spacer. Overall, the polysulfabetaine coatings with the shorter ethylene spacer show higher resistance against non‐specific adsorption of proteins, in particular of lysozyme, or against colonization by diatoms. This may result from the higher steric constraints of the polymer attached zwitterions, favoring particularly advantageous conformations. Moreover, a shorter spacer between the oppositely charged ionic groups of the zwitterionic moiety reduces the settlement of cyprid larvae more effectively. Poly(sulfabetaine methacrylate)s are explored as coatings against marine biofouling, investigating the effect of the spacer groups that separate the cationic ammonium from the anionic sulfate groups, and those separating the zwitterionic moiety from the backbone. While the shorter ethylene spacers provide the highest fouling‐resistance, the spacer type, inter‐charge or betaine‐to‐backbone, controls which particular organism is most effectively prevented from adhesion.
... Additionally, diatoms have strong adhesive properties due to both intrinsic cell adhesion abilities, as in the case of certain Nitzschia species (Laviale et al., 2019), and mucilage strand properties leading to efficient sediment stabilization (e.g., Vos et al., 1988). In the latter case, similarly to bacterial mucilage, high amounts of uronic acids in EPS appear to be the primary factor promoting adhesiveness in diatoms (Sutherland, 2001;de Brouwer et al., 2005;Poulsen et al., 2014). The end result is that some microbial mat and associated morphologies may leave records in sediments and, at last, in the sedimentary record (e.g., Gerdes, 2007). ...
In the only salt evaporation pond retaining its natural setting of the historic Salina di Cervia (Italy), the northernmost salterns of the Mediterranean area, a number of potentially preservable textures derive from the interactions between photosynthetic mat producers and the sedimentary substrate. These morphologies occur at the beginning of the taphonomic processes when repeated emerged-submerged conditions take place. In these conditions the cohesive nature of the diatom- and cyanobacterial-derived mucilage favours the stabilization of otherwise ephemeral structures. Surface micromorphologies for which diatoms and cyanobacteria have played some active role when still living in the soft microlayer and down to the sediment-water interface, such as during the gliding motility, can overcome the surface layer of most intense mixing (i.e., the taphonomically active zone) and keep traces of them in the fossil record either as body fossils or as texture contributors. Tiny microbial-derived remnants, such as filaments and biofilm strands of halotolerant microorganisms, while fragile upon their formation, can therefore stabilize as biosignatures when combined with salt precipitation. Halophilic and halotolerant ecosystems are models for life in extreme environments (analogue sites) with similarity to those strongly suspected to occur and/or have occurred on Mars and on other planetary bodies. The study of hypersaline systems such as Salina di Cervia which harbour diverse and abundant microbial life, can be relevant for astrobiology since it allows the investigation of potential biosignatures and their preservation, and of further understand the range of conditions and the planetary processes sustaining potentially habitable systems.
