| | Category | MI | L20 | Diatoms: Nature's Nano Architects |
| | Abstract | Diatoms are unicellular organisms, and are considered to be some of |
| | nature’s finest architects. Diatoms engineer intricate shells of amorphous |
| | silica on the nanometer scale. However, little is known about how such |
| | detailed construction is carried out at such a small scale. Due to their |
| | photosynthetic capabilities and abundance, diatoms have a profound |
| | impact on the delicate equilibrium of the environment. They account for |
| | approximately 45% of the Earth’s oceanic energy production, and are |
| | responsible for nearly 20% of global carbon fixing capacity. Therefore, |
| | understanding the unique cellular processes of diatoms will provide us |
| | with new insights into mineral deposition in larger animals, such as the |
| | deposition of bone in humans. Since different species of diatoms construct |
| | markedly different exoskeletons, I hypothesized that species-specific soft |
| | proteinaceous structures may exist in diatoms, controlling and regulating |
| | the precise deposition of silica. In the current study, I provide evidence for |
| | the first time of a pore like protein complex in the Thalassiosira |
| | pseudonana diatom cell membrane, explored using atomic force |
| | microscopy. The primary objective of this study was to understand the |
| | precise mechanism of the deposition of the silica exoskeleton, or frustule, |
| | in diatoms. Preceding the formation of the silica structure, silica in the form |
| | of silicic acid is taken in by the diatom from its environment and collected in |
| | a large vesicle. The vesicle docks at the cell membrane and releases its |
| | contents to form the shell of the diatom. The molecular mechanism of |
| | release and arrangement of the frustule was the focus of the study. Using |
| | high-resolution electron and atomic force microscopy, both the frustules |
| | and the cell membranes of diatoms were examined. Examination using |
| | AFM yielded a circular protein complex on the diatom cell membrane. T- |
| | SNARE s or target proteins are proteins that are required for the secretory |
| | vesicle docking and fusing process in cells. Western blots were used to |
| | validate the presence of T-SNARE proteins in diatoms, and T-SNAREs |
| | were consistently found in analyses of centrifuged diatom pellets. The |
| | “pore” structure was positively identified as the silica secretory machinery |
| | in this unicellular organism. Further analysis of this complex could yield the |
| | answers to many questions, including the details of the deposition of |
| | mineralized osseous tissue in vertebrate bone structure. New frontiers in |
| | the rapidly expanding field of biological mimicry or biomimetics would be |
| | established, especially in nano-scale processes such as drug delivery, the |
| | development of catalysts for use in industry, and even nano electronics |
| | and robotics. Furthermore, the large role that diatoms play in our |
| | environment will allow us to use the knowledge gained from such studies |
| | to reverse many of the negative impacts of environmental pollution to our |
| | planet, and the use of diatoms as an energy source and for global carbon |
| | fixation. |
| | Bibliography | Almqvist N, Delamo Y, Smith BL, Thomson NH, Bartholdson A, Lal R. et al. |
| | Micromechanical and structural properties of a pennate diatom investigated |
| | by atomic force microscopy. J. Microsc. 2001; 202: 518-532.Blank GS, |
| | Sullivan CW. Diatom mineralization of silicic acid VI. The effects of |
| | microtubule inhibitors on silicic acid metabolism in Navicula saprophila. J |
| | Phycol. 1983; 19: 39-44. |