We investigate two-dimensional (2D) assembly of the icosahedral turnip yellow mosaic virus (TYMV) under cationic lipid monolayers at the aqueous solution–vapor interface. The 2D crystallization of TYMV has been achieved by enhancing electrostatically induced interfacial adsorption, an approach recently demonstrated for another virus. In situ X-ray scattering reveals two close-packed 2D crystalline phases of TYMV that are distinct from the previously reported hexagonal and centered square ( 2×2) arrays of TYMV. One of the newly observed phases arises from either a dimeric double-square (2 × 1) or tetrameric square (2 × 2) unit cell. The other is a rhombic crystal with a lattice angle of 80°. The two observed crystal phases are substantially less dense (by over10%) than a 2D lattice of TYMV could be according to its known size and shape, indicating that local anisotropic interparticle interactions play a key role in stabilizing these crystals. TYMV’s anisotropy attributes and numerical analysis of 2D arrays of virus-shaped particles are used to derive a model for the rhombic crystal in which the particle orientation is consistent with the electrostatic lipid–TYMV attraction and the interparticle contacts exhibit steric complementarity. The interplay between particle anisotropy and packing is contrasted between the rhombic crystal model and the square ( 2×2) crystal. This study highlights how the high symmetry and subtle asphericity of icosahedral particles enrich the variety and complexity of ordered 2D structures that can be generated through self-assembly.

Chemical addressability of viral particles has played a pivotal role in adapting these biogenic macromolecules for various applications ranging from medicine to inorganic catalysis. The consistent multimeric assemblies dictated by its genetic code, facile large scale production, lack of observable toxicity in humans, Cowpea mosaic virus possesses multiple features that are advantageous for the next generation of virus-based nanotechnology. Herein, the chemistry of the viral particles is extended with the use of Cu-free strain-promoted azide-alkyne cycloaddition reaction, or SPAAC reaction. The elimination of Cu, its co-catalyst and reducing agent simplifies the reaction scheme to a more straightforward approach, which can be directly applied to living systems. As a proof of concept, the viral particles modified with the aza-dibenzylcyclooctynes functional groups are utilized to trigger and amplify a weak fluorescent signal (azidocoumarin) in live cell cultures to visualize the non-natural sugars. Future adaptations of this platform may be developed to enhance biosensing applications.

Escherichia coli is a well-studied bacterium that can be found in many niches, such as industrial wastewater, where the concentration of nickel can rise to low-millimolar levels. Recent studies show that nickel exposure can repress pyochelin or induce pyoverdine siderophore production in Pseudomonas aueroginosa. Understanding the molecular cross-talk between siderophore production, metal homeostasis, and metal toxicity in microorganisms is critical for designing bioremediation strategies for metal-contaminated sites. Here, we show that high-nickel exposure prolongs lag phase duration as a result of low-intracellular iron levels in E. coli. Although E. coli cells respond to low-intracellular iron during nickel stress by maintaining high expression of iron uptake systems such as fepA, the demand for iron is not met due to a lack of siderophores in the extracellular medium during nickel stress. Taken together, these results indicate that nickel inhibits iron accumulation in E. coli by reducing the presence of enterobactin in the extracellular medium.