Study the nanotopography of the internal and external surface of the valve using AFM [1.34]. Some features within the valve could be observed through SEM, or even optical microscope if large enough, such as the frustule surface topology, which could be flat or rather undulated, wrinkled, or containing groves; however, other nanotopographical features cannot be revealed without a tool like AFM such as the dome shape of the cribellum in [1.34].
8. To understand the relationships of frustule elements and the inner ultrastructure of a given valve, or girdle bands, FIB-SEM should be considered (see example in Figure 1.6). For more advanced understanding, one of the methods mentioned for 3D reconstruction should be used [1.41] such as the 3D reconstruction of the 2D image series resulting from FIB-SEM. Through these techniques, a clear understanding of, for example, the multilayer nature of the valve could be obtained.
Afterward, all the ultrastructure details from inside and outside become well-known.
1.4 Conclusion
Diatom morphology could be an interesting topic for students; however, many challenges in the field usually keep them away from getting a deeper understanding. This is a major opportunity, since only 15,000–20,000 species have been identified [1.46], out of very large number of extant and fossil species. Recently, the developed tools, especially AFM and FIB-SEM, can make the complex 3D ultrastructure of diatoms more accessible; however, very few attempts have been recorded in literature. For both the beginners and professionals, many unrevealed secrets of diatom morphology and morphogenesis are still kept hidden, which needs more progress in the field. The study of diatom morphology could also inspire material scientists and engineers especially as the functions beyond morphology are revealed. A comprehensive tutorial suitable for different specialists could be helpful to put the beginners on the right track. Here, we only provided a potential introduction for such tutorial.
Acknowledgements
We would like to express our gratitude to the editors for their understanding and help; we are grateful for the meaningful suggestions of reviewers. KMM’s work on this project was supported by funding from EPD, State of Georgia, USA. MG is very grateful to Dr. Mary Ann Tiffany for giving him the micrographs in Figure 1.1.
References
[1.1] Bahls, L., Boynton, B., Johnston, B., Atlas of diatoms (Bacillariophyta) from diverse habitats in remote regions of western Canada. Phytokeys, 105, 1–186, 2018.
[1.2] Bishop, I.W., Esposito, R.M., Tyree, M., Spaulding, S.A., A diatom voucher flora from selected southeast rivers (USA). Phytotaxa, 332, 2, 101–140, 2017.
[1.3] Brotosudarmo, T.H.P., Wibowo, A.A., Heriyanto, Adhiwibawa, M.A.S., Single cells diatom Chaetoceros muelleri investigated by homebuilt confocal fluorescence spectro-microscopy, in: Third International Seminar on Photonics, Optics, and Its Applications, A. Nasution and A.M. Hatta (Eds.), p. 11044, 2019.
[1.4] Cohn, S.A., Manoylov, K.M., Gordon, R. (Eds.), Diatom Gliding Motility[DIGM, Volume in the series: Diatoms: Biology & Applications, series editors: Richard Gordon & Joseph Seckbach, In preparation], Wiley-Scrivener, Beverly, MA, USA, 2020.
[1.5] Cox, E.J., Identification of Freshwater Diatoms from Live Material, Chapman & Hall, London, 1996.
[1.6] Diatom Flora of Britain and Ireland, Glossary, Wales, UK, 2020, https://naturalhistory.museumwales.ac.uk/diatoms
[1.7] Diatoms of North America, Glossary, USA, 2020, https://diatoms.org/glossary.
[1.8] Falkowski, P.G., Barber, R.T., Smetacek, V., Biogeochemical controls and feedbacks on ocean primary production. Science, 281, 5374, 200–206, 1998.
[1.9] Ghobara, M.M., Mazumder, N., Vinayak, V., Reissig, L., Gebeshuber, I.C., Tiffany, M.A., Gordon, R., On light and diatoms: A photonics and photobiology review[Chapter 7], in: Diatoms: Fundamentals & Applications[DIFA, Volume 1 in the series: Diatoms: Biology & Applications, series editors: Richard Gordon & Joseph Seckbach], J. Seckbach and R. Gordon (Eds.), pp. 129–190, Wiley-Scrivener, Beverly, MA, USA, 2019.
[1.10] Gordon, R., Kling, H.J., Sterrenburg, F.A.S., A guide to the diatom literature for diatom nanotechnologists. J. Nanosci. Nanotechnol., 5, 1, 175–178, 2005.
[1.11] Kaczmarska, I., Bates, S.S., Ehrman, J.M., Léger, C., Fine structure of the gamete, auxospore and initial cell in the pennate diatom Pseudo-nitzschia multiseries (Bacillariophyta). Nova Hedwig., 71, 3–4, 337–357, 2000.
[1.12] Molino, P.J. and Wetherbee, R., The biology of biofouling diatoms and their role in the development of microbial slimes. Biofouling, 24, 5, 365–379, 2008.
[1.13] Romann, J., Valmalette, J.C., Royset, A., Einarsrud, M.A., Optical properties of single diatom frustules revealed by confocal microspectroscopy. Opt. Lett., 40, 5, 740–743, 2015.
[1.14] Sato, S., Nanjappa, D., Dorrell, R.G., Vieira, F.R.J., Kazamia, E., Tirichine, L., Veluchamy, A., Heilig, R., Aury, J.-M., Jaillon, O., Wincker, P., Fussy, Z., Obornik, M., Munoz-Gomez, S.A., Mann, D.G., Bowler, C., Zingone, A., Genome-enabled phylogenetic and functional reconstruction of an araphid pennate diatom Plagiostriata sp. CCMP470, previously assigned as a radial centric diatom, and its bacterial commensal. Sci. Rep., 10, 1, 9449, 2020.
[1.15] Smol, J.P. and Stoermer, E.F., Glossary, acronyms, and abbreviations, in: The Diatoms: Applications for the Environmental and Earth Sciences, 2nd, J.P. Smol and E.F. Stoermer (Eds.), pp. 614–654, Cambridge University Press, Cambridge, 2010.
[1.16] Spaulding, S., Esposito, R., Lubinski, D., Horn, S., Cox, M., McKnight, D., Alger, A., Hall, B., Mayernick, M., Whittaker, T., Yang, C., Antarctic Freshwater Diatoms: Glossary, 2009, http://huey.colorado.edu/diatoms/about/glossary.php.
[1.17] Tiffany, M.A. and Nagy, S.S., The beauty of diatoms[Chapter 3], in: Diatoms: Fundamentals & Applications[DIFA, Volume 1 in the series: Diatoms: Biology & Applications, series editors: Richard Gordon & Joseph Seckbach], J. Seckbach and R. Gordon (Eds.), pp. 31–40, Wiley-Scrivener, Beverly, MA, USA, 2019.
[1.18] Witkowski, A., Gomes, A., Mann, D.G., Trobajo, R., Li, C.L., Barka, F., Gusev, E., Dąbek, P., Grzonka, J., Kurzydłowski, K.J., Zglobicka, I., Harrison, M., Boski, T., Simonsenia aveniformis sp. nov. (Bacillariophyceae), molecular phylogeny and systematics of the genus, and a new type of canal raphe system. Sci. Rep., 5, #17115, 2015.
[1.19] Tiffany, M.A., Epizoic and Epiphytic Diatoms, in: The Diatom World. Cellular Origin, Life in Extreme Habitats and Astrobiology, vol. 19, J. Seckbach and P. Kociolek (Eds.), Springer, Dordrecht, 2011.
[1.20] Gillard, J., Frenkel, J., Devos, V., Sabbe, K., Paul, C., Rempt, M., Inz, D., Pohnert, G., Vuylsteke, M., Vyverman, W., Metabolomics Enables the Structure Elucidation of a Diatom Sex Pheromone. Angew. Commun., 52, 3, 1056–1056, 2013.
[1.21] Bedoshvili, Y.D. and Likhoshway, Y.V., Cellular Mechanisms of Diatom Valve Morphogenesis, in: Diatoms: Fundamentals and Applications, Seckbach, J. and Gordon, R. (Eds.), 2020.
[1.22] Anonymous, Two letters from a gentleman in the country, relating to Mr. Leuwenhoeck’s letter in Transaction, No. 283. Philos. Trans. R.
