Welcome to Curiosity Minisodes—where we tackle high-order questions from high-yield topics in 10 minutes or less.

Today, we’re digging into biological classification.

Hosted by Michael McNeil.

Our cover art for this episode is based on the watercolor illustration "Last Universal Common Ancestor" by David Goodsell. RCSB Protein Data Bank. doi: 10.2210/rcsb_pdb/goodsell-gallery-035

Follow Curiosity on Instagram (www.instagram.com/newwaytowonder) and YouTube (youtube.com/@curiosityeducation) and share your thoughts and burning science questions with our host by emailing contact@mdmcneil.com.

Why does taxonomy matter—and what can it teach us about our place among life on Earth? In Part 1 of our two-part exploration of eukaryotic cells, we unpack the history of classification, from Aristotle to Linnaeus to us, and take a closer look at how emergence supports the intricacy and complexity of our experience of life.

Hosted by Michael McNeil. Special thanks to T. Aleman, A. Graulau, J. Ishimwe, and J. Reid.

Our cover art for this episode is based on the prints of the biologist Ernst Haeckel.

Follow Curiosity on Instagram (www.instagram.com/newwaytowonder) and YouTube (youtube.com/@curiosityeducation) and share your thoughts and burning science questions with our host by emailing contact@mdmcneil.com.

0:00 - Part 0: Introduction

1:50 - Part 1: Biological Emergence

7:07 - Part 2: History of Biological Classification

25:13 - Part 3: Eukaryotic Taxonomy

Earth is home to an estimated 10 million forms of life, but we can't see most of them with our own eyes. In today's episode, we'll take a peek behind the curtain. We'll explore the bizarre structures, lethal defenses, and fascinating mating habits of bacteria. And we'll finally get introduced to archaea, the newest, oddest, and least understood members of the family tree.

0:00 - Part 0: Introduction

5:56 - Part 1: General Prokaryotic Features

• Prokaryotes vs. Eukaryotes
• Morphological Diversity
• Cell Wall Characteristics
• Cell Membranes, Lipopolysaccharide, and Lipid A

26:02 - Part 2: Gram Staining

• The Gram Stain Protocol
• Gram Staining Insights

34:23 - Part 3: Additional Prokaryotic Structures

• Capsules and Tonicity
• Endospores
• Fimbriae
• Pili
• Non-Flagellar Locomotive Structures
• Flagella and Taxis

51:30 - Part 4: Prokaryotic Growth and Metabolism Considerations

• Autotrophs, Heterotrophs, Chemotrophs, and Phototrophs
• Aerobes vs Anaerobes

53:32 - Part 5: Prokaryotic Reproduction and Gene Exchange

• Binary Fission
• Transduction
• Transformation
• Conjugation

1:04:34 - Part 6: Bacteria vs Archaea

• The First Archaebacteria
• Difficulties in Studying Archaea

References + Further Reading

- Bardy, S. L., Ng, S. Y. M., & Jarrell, K. F. (2003). Prokaryotic motility structures. Microbiology, 149(2), 295-304. https://doi.org/10.1099/mic.0.25948-0

- Casson, H. N. (1911). The history of the telephone. A. C. McClurg.

- Clark, M. A., Douglas, M., & Choi, J. (2018). Biology 2e. OpenStax.

- Fagan, R. P. & Fairweather, N. F. (2014). Biogenesis and functions of bacterial S-layers. Nature Reviews Microbiology, 12, 211-222. https://doi.org/10.1038/nrmicro3213

- Gao, S. ... & Wang, Y. (2024). Bacterial capsules: Occurrence, mechanism and function. NPJ Biofilms and Microbiomes, 10(21). https://doi.org/10.1038/s41522-024-00497-6

- Hersh, D. S. ... & Kim, A. J. (2016). Evolving drug delivery strategies to overcome the blood brain barrier. Current Pharmaceutical Design, 22(9), 1177-1193. http://dx.doi.org/10.2174/1381612822666151221150733

- Lambert, P. A. (2002). Cellular impermeability and uptake of biocides and antibiotics in Gram-positive bacteria and mycobacteria. Journal of Applied Microbiology, 92(s1), 46S-54S. https://doi.org/10.1046/j.1365-2672.92.5s1.7.x

- Mole, B. (2015). Bacteria staining method has long been misexplained. Science News. https://www.sciencenews.org/article/bacteria-staining-method-has-long-been-misexplained

- Nath, D. (2008). The prokaryotic cytoskeleton. Nature Reviews Molecular Cell Biology, 9(Suppl 1), s19. https://doi.org/10.1038/nrm2582

- National Geographic Society. (2023). Feb 1, 1884 CE: First publication of the Oxford English Dictionary. https://education.nationalgeographic.org/resource/first-publication-oxford-english-dictionary/

- Pallin, D. J., & Wright, J. (2022). MCAT: Biology review (3rd ed.). The Princeton Review.

- Pöhl, S. ... & Thanbichler, M. (2024). An outer membrane porin-lipoprotein complex modulates elongasome movement to establish cell curvature in Rhodospirillum rubrum. Nature Communications, 15(7616). https://doi.org/10.1038/s41467-024-51790-z

- Richard, S. (2020). How Helicobacter stays helical. Fred Hutch Cancer Center. https://www.fredhutch.org/en/news/center-news/2020/01/salama-helicobacter-pylori-shape.html

- Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., & Orr, R. B. (2021). Campbell: Biology (12th ed.). Pearson.

- Woese, C. R. & Fox, G. E. (1977). Phylogenetic structure of the prokaryotic domain: The primary kingdoms. Proceedings of the National Academy of Sciences, 74(11), 5088-5090. https://doi.org/10.1073/pnas.74.11.5088

Correction

- At 34:49, Michael misspoke. Capsules connect to peptidoglycan in Gram-positive bacteria and to the outer cell membrane in Gram-negative bacteria, not the other way around.

Special Thanks

- University of Wisconsin-Madison

- U.S. National Park System

- T. Aleman, J. Ishimwe, J. Wilson, and A. Graulau