Chemical Reactions, CR 1: Predicting Reactions (HS), Life Science, Natural Selection & Evolution, Non-NGSS Articles, NSE 4: Adaption (HS), S&F 1: DNA to Proteins (HS), S&P 1: Periodic Table Patterns (HS), S&P 4: Molecule Traits (HS), Structure & Properties of Matter, Structure and Function

The making of natural iron sulfide nanoparticles in a hot vent snail

https://www.pnas.org/content/116/41/20376

SUMMARY: The scaly-foot snail also known as Chrysomallon squamiferum is unique in that it makes iron sulfide nanoparticles. Chemically, most creatures who are only able to make minerals (biomineralization) using oxygen. The scaly-foot snail is able to do this in the absence of oxygen, a method that scientists are keen on understanding as it has industrial implications for humans. This study hypothesizes that there are 3 possible ways the snails make these nanoparticles:

  1. The particles form by themselves because of the nature of the hydrothermal vents the snails live in.
  2. Bacteria living on the surface of the snails make these nanoparticles.
  3. The snails are controlling the biomineralization of these iron sulfide nanoparticles.

Scientists discovered that number three was correct. The snails create a shell that is a conchiolin protein-matrix foundation filled with columns that are rich in sulfur. This specialized structure allows the iron sulfide nanoparticles to naturally form when iron ions in the water diffuse into the shell. Even when the snails are dead, these nanoparticles will still form on the surface… as long as the dead snails are in an iron-rich environment. 

LESSON COMMENTS: Chemistry teachers will find this article very useful. It covers basic concepts such as electronegativity, redox reactions, and ions/ionic bonds. If you’re teaching students about the scientific method, the second to last paragraph of the introduction is a great example of proposing different hypotheses. The results section is a bit dense, so for students who aren’t used to reading scientific literature, it’s perfectly fine to skip to the discussion section. This article can be used in either a chemistry or biology class, but it would work even better for teachers looking to do a joint biology/chemistry project or lesson.

Okada, S., Chen, C., Watsuji, T. O., Nishizawa, M., Suzuki, Y., Sano, Y., Bissessur, D., Deguchi, S., & Takai, K. (2019). The making of natural iron sulfide nanoparticles in a hot vent snail. Proceedings of the National Academy of Sciences of the United States of America, 116(41), 20376–20381. https://doi.org/10.1073/pnas.1908533116

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