What makes algae reproduce sexually?

Microbiologist Kimberly Halsey discusses the accidental discovery of sexually reproducing diatoms in her lab.

Xochitl Garcia
Jul 27, 2017 · 3 min read

Vocabulary: diatom, asexual reproduction, sexual reproduction, cell division

Next Generation Science Standards: SEP1- Asking Questions and Defining Problems, CC2- Cause and Effect: Mechanism and Explanation, LS1.B: Growth and Development of Organisms, and LS3.A: Inheritance of Traits.

Circle of Diatoms on a slide. Credit: Wipeter (Own work) [CC-BY-SA-3.0], via Wikimedia Commons

Diatoms are a type of single-celled algae found all over the world. Considered model organisms, they’re a staple in labs studying ocean water quality. Indeed, they’re as ubiquitous in microbiology research as lab mice are in human-health studies.

Diatoms are so well-studied that some facts about them seem irrefutable, like their asexual method of reproduction by cell division. But by happy accident, researchers at Oregon State University recently discovered a group of centric diatoms that reproduce sexually when stimulated by the presence ammonium in the surrounding water. Kimberly Halsey, an assistant professor in the Department of Microbiology at Oregon State University, joins Ira to discuss how scientists overlooked something so fundamental about an organism they thought they knew so well.

Audio Excerpt “A Peek Into The Sex Lives of Algae,” July 14, 2017. (Original Segment)

Print this segment transcript.

Questions

  • These particular diatoms usually reproduce asexually, through cell division. Describe the difference between the genes of the offspring of sexual versus asexual diatom reproduction.

“The most exciting phrase to hear in science, the one that heralds the most discoveries, is not “Eureka!” (I found it!) but “That’s funny…” — Isaac Asimov

  • Explain how the phrase above relates to Kimberley Halsey and Eric Moore’s research on diatoms.

Activity Suggestions

  • Explore the biology of aquatic plants like diatoms with this activity where you grow algae in a bottle and look at the effect of nutrients and light levels on growth. Have students go further by relating this experiment back to the one done in the interview. Can they create a new experiment by incorporating the variable they investigated with their bottle(light and/or nutrients) into the research on diatom sexual reproduction done by Kimberly Halsey’s lab?

Additional Resources

Check out this sand under a microscope. Can you spot the diatoms in the sand?

Check out the original paper! Moore ER, Bullington BS, Weisberg AJ, Jiang Y, Chang J, Halsey KH (2017) Morphological and transcriptomic evidence for ammonium induction of sexual reproduction in Thalassiosira pseudonana and other centric diatoms. PLoS ONE 12(7): e0181098.

A Thalassiosira pseudonana diatom oogonium (egg cell) beginning to expand through the cell wall. Artificial coloring denotes chlorophyll (blue) and DNA (red). Credit: Oregon State University

Science Friday Spoonfuls

The latest and greatest science news from public radio’s Science Friday, ready for classroom use.

Xochitl Garcia

Written by

Education program assistant @scifri and 2015 #grosvenorteacherfellow @NatGeoEducation. #STEM Educator obsessed with food and board games.

Science Friday Spoonfuls

The latest and greatest science news from public radio’s Science Friday, ready for classroom use.

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