Feliz día: International Women’s Day

Many creative and brave women shaped the way we understand the world, including many women scientists.

Recently I bought a new computer, and I decided to name it after a groundbreaking woman scientist. Marie Curie, who pioneered radioactivity came to mind, as did Rosalind Franklin, who, independent of Watson and Crick, determined the structure of DNA using x-ray crystallography. But then… I was stumped.

Even as a scientist I could only name two famous women scientists who shaped my understanding of science. I was astonished I could not name more without a google search. I admire many women currently working on cutting-edge science, but I knew many lady scientists significantly contributed to developing the ideas that we teach in intro-level courses.

Luckily, as a teaching assistant, I get to learn introductory biology all over again. One day in principles of biology lecture, my advisor described the concept of how mitochondria and chloroplasts came to exists as organelles inside of a cell- and that Lynn Margulis, despite grief from her male colleagues, solidified the endosymbiotic theory—a way of thinking that is essential to our current understanding of biology.

Here is why endosymbiosis is so cool:

Remember learning about all of the organelles inside of a cell? And about how the mitochondria is the “powerhouse of the cell”? Plants have a “make-your-own-food-from-sunlight” organelle: chloroplasts. Both mitochondria and chloroplasts are surrounded by a second membrane and contain their own circular DNA, which led Lynn Margulis to propose the idea that these organelles were originally prokaryotes, like bacteria, which were engulfed by another cell! While inside the cell, this prokaryote/ organelle ancestor paid enough “rent” by producing ATP or creating sugars from sunlight, so the landlord cell kept its tenants around.

An entire domain of life began- eukaryotes. (We belong to this domain…so does your cat.)

Yet, as I hinted earlier, this theory explaining the origin of eukaryotes and the organelles providing the energy was not accepted with open arms. I am not sure if the theory would be equally as contested if a man proposed it, but as a woman, Lynn’s publication On the Origin of Mitosing Cells was rejected 15 times, and even after it was accepted and printed in 1967, she still was not widely accepted by her male colleagues who thought her idea was ridiculous.

But with sheer courage she persisted, and now overwhelming evidence supports the endosymbiotic origin for the mitochondria and chloroplast. First, if you take all of the mitochondria or chloroplasts out of a cell, the cell cannot make more, which implies the ancestor cell took it in to begin with. Not only do both organelles have their own DNA resembling that of bacteria, but when scientists look at the DNA sequences, the base pairs line up well with current prokaryotes. Cyanobacteria is the chloroplast’s closest relative, even though chloroplasts are found in plants!

I can’t even imagine what we would teach students about how eukaryotes gained extra organelles, which gave this domain of life access to energy that enabled the crazy diversity we see today.

Lynn continued in her career by showing how symbiotic interactions—organisms interacting with one another—can act as a major evolutionary force.  My own research depends on this concept, and involves a form of endosymbiosis: bean plants take up bacteria into their roots that turn atmospheric nitrogen into a form the plant can use. This cooperation between plants and bacteria enables both to flourish.

This weekend I was honored to participate as a mentor for a Women in Science day event: girls 12-18 years old toured Genentech, a leading biotech company and talked with a wide variety of scientists to learn about possible careers. I was struck by the momentum behind encouraging girls to pursue science, and the confidence that there is power in women’s perspectives in creating innovative science.

“Life did not take over the globe by combat, but by networking”- Lynn Margulis (and Dorion Sagan)


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