Periodic Reporting for period 4 - BioSilica (Materials synthesis in vivo – intracellular formation of nanostructured silica by microalgae)
Periodo di rendicontazione: 2024-07-01 al 2024-12-31
Silica (basically glass) is one of the most useful and abundant materials we encounter in our everyday life. It is widespread in natural settings and in traditional industrial applications. Maybe more importantly it is now being a major player in advanced nanomaterial developments for technology. A major goal of material engineering is to control the nanoscale shapes and properties of this inorganic solid. However, this is very difficult to achieve as conventional synthesis involves harsh chemical conditions and lead to simple silica structures. On the other hand, very simple organisms have evolved a magnificent ability to form silicified structures with tightly controlled properties. One such group is diatoms, the most abundant unicellular algae in the oceans, which form an intricate cell wall that is made of silica via a physiological process. The goal of BioSilica project is to achieve a mechanistic understanding of diatom silicification to the level that it will enable us to engineer this process to yield silica product with desirable products. In the long run we envision that it will be possible to genetically encode the needed silica properties for a specific application into the organism DNA, which then will allow to ‘grow’ such nanomaterials using only sunlight and seawater. What can be more ‘green’ than that?!
After concluding the experimental section of the project, we can conclude that we have now more detailed understanding about the mechanism of diatom silicification. Specifically, we have come to know that the major controller of the process is the engulfing membrane that is regulating the transport for mineral formation, the morphogenesis of the structure, and its exocytosis to the cell surface. This knowledge will enable future work to target specific machineries inside the cells for intelligent design of the silica elements. A persistent challenge is the availability of genetic tools, which are still rudimentary and limit the scope of such engineering avenues.
After concluding the experimental section of the project, we can conclude that we have now more detailed understanding about the mechanism of diatom silicification. Specifically, we have come to know that the major controller of the process is the engulfing membrane that is regulating the transport for mineral formation, the morphogenesis of the structure, and its exocytosis to the cell surface. This knowledge will enable future work to target specific machineries inside the cells for intelligent design of the silica elements. A persistent challenge is the availability of genetic tools, which are still rudimentary and limit the scope of such engineering avenues.
In this project, we have pioneered the use of advanced structural biology techniques for the study of biological mineralization. We focused on cryo electron microscopy, which is a suite of instrumentation and modalities that allow to image living cells in their native state and with 3D nanometer scale resolution. This approach gave us the opportunity to interrogate the environment in which the inorganic materials forms within the cell. We have collected large amount of data that enable the initial seeds for a new dogma for diatom silicification. We see that the most influential factor of the silicification process is the close proximity between the material and the membranes of the organelle that produces it. This confined environment is allowing the membranes to act as a process-directing agent that is responsible for many aspects of the process, from the transport of the inorganic building blocks to the molding of the convoluted shapes. in other avenues of this project, we have elucidated new mechanisms that diatoms use to exocytose their silica elements and their ability to silicify even outside the cell membrane.
In this project, we have used our capabilities to derive specific mechanisms related to diatom silicification. This was an effort beyond the state of the art as structural dynamics were never explored for such biological mineralization processes. We elucidated how the cell can extrude the huge silica element without compromising its own integrity, how biophysical factors and genetic mutations can yield specific modifications to the silica properties, and how synthetic chemical experiments in which we can reach complete understanding of the chemical process, reveal the fundamental chemistry inside cells. These results already change the way we think about harnessing biological materials synthesis for specific applications, and in the base for various new research projects.