The Basic Science Research Concept

“So are you trying to make plants more defended?”

This is often the first question I encounter when I share my research questions with anyone that does not spend their work life thinking about plants. Before the conversation can get much further, I find it helps to introduce the difference between basic science research and applied research.

Both are important, but it is easier for people to connect with applied research: research designed to improve the way humans live. However, many of the solutions we use today came as a result of discoveries from basic science research: research designed to understand the way something works for the sake of understanding.

Like what?

PCR: the technology that lets us duplicate tiny amounts of DNA, was only possible because a scientist was curious about how acidic and hot Yellowstone hot springs could be for bacteria to survive. Bacteria flourishing at high temperatures have DNA too, and the enzymes that could replicate DNA despite the heat were eventually extracted and were able to withstand the hot temperatures in PCR.

Efficient building design: scientists were curious about the structure of termite mounds, which can maintain a constant temperature despite the heat of the desert. The results from these studies were used to construct a building in Zimbabwe (The Eastgate Centre) that uses 90% less energy.

Velcro, the ubiquitous adhesive found on light-up shoes, was inspired by plant hook-shaped hairs.

And the list goes on. The moral of the story is that technology gets along well with natural selection, but first we have to understand how it all works.

My research goal is to understand how plant-insect interactions change as a result of the chemistry within the plants that have a symbiotic relationship with nitrogen-fixing bacteria. I spend my time at my desk wondering about how and when plants will use their resources to make the stuff that protect them- either directly by making poisonous chemicals, or indirectly, by sending volatile compounds into the air to communicate with the predators of their attackers.

Instead of trying to get plants to do anything, my goal is to understand what they actually do on their own- to understand the unknown aspects of their biology.

Do these bacteria play an important role in the food web by altering plant-insect interactions? My research will let you know.

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The Front of the Train

One major goal in science education is to teach students how to think like a scientist. In many cases, this means teaching science the way we do science, which is often through inquiry and research. But before students can strike out in the lab on their own with a pipette and a new question to answer, they need to learn the foundational information that came from research before them.

I like to think of this challenge using a visual from Zen and the Art of Motorcycle Maintenance. The front of a train represents the interface between the past experiences we carry with us and the unknown track ahead. Even while being hung up on a past memory or anxious about what may come, the front of the train is what we continually witness: here and now, moving through time.

Science research is also the front of the train, where discovery happens. The challenge in science education is starting at the back of the train and working forwards to cover all of where we have been (which is usually presented in textbook format), in order to get students to the front of the train, asking their own questions and making their own connections.

However, covering the entire textbook before getting to the inquiry and connecting part creates a problem: we are training students to passively ride along like a train car as we move forward in what we know, until suddenly, students make it to the front and come up against what we do not yet know. If students have not practiced asking questions or thinking about how to figure out the next step, when they do conduct research, they are not prepared to discuss it.

A true discussion explains how this new piece of information fits into our understanding of the world—how the shape of our overall understanding changes with this new dimension. To connect new observations to the big picture requires not only extensive background knowledge on the subject, but also creativity. Drawing lines that never existed or imagining a differently-shaped perspective are essential skills in science.

I watched this happen as a high school student I was mentoring in research presented her work to her high school. She was able to introduce complicated biology topics: plant secondary metabolism and symbiosis with nitrogen-fixing bacteria, describe what she did in the lab, and even interpret a few graphs. But then she pulled up a slide titled “discussion” and she listed potential sources of error, including the size of the pots, and even “human error” in her count data. I was baffled by this until a colleague reminded me that the science most students do in school has a known outcome, and if data do not match that outcome, students are trained to explain why not by citing sources of error that caused results to stray from what they were supposed to find.

This is an important paradigm shift. A well-designed, controlled experiment does not have sources of error because the result is not yet known. So how should students discuss and interpret unknown results?

A true discussion explains how this new piece of information fits into our understanding of the world—how the shape of our overall understanding changes with this new dimension. To connect new observations to the big picture requires not only extensive background knowledge on the subject, but also creativity. Drawing lines that never existed or imagining a differently-shaped perspective are essential skills in science.

So how do we teach these skills if we have to cover sufficient background info for students to grasp the current state of science knowledge with enough proficiency to draw new connections? A formal answer to this question is a recipe for grant funding, but I think any educator intuitively knows the secret ingredient:

Learning how to ask questions.

Question confidence is where science progresses- where the massive train of knowledge comes up against the wind at the front. This also explains why many funding agencies highlight the importance of scientists coming from diverse backgrounds: to ask diverse questions, use creativity to draw conclusions and serve as role models for a diverse group of students learning how to gain their own question confidence.

Feel free to offer resources or ideas about how to help more students think like a scientist.

How I Became a Scientist

Recently I found myself at a table across from wide-eyed students at a job fair asking me how I became a scientist.  I knew immediately that answer to their question was my experience at Outdoor School as a high school student leader. Here is a great video from Oregon Field Guide that shows what Outdoor School looks like.

At one point, every sixth grade student in Oregon attended Outdoor School, which is one reason Portlanders and Oregononians claim the “outdoorsy” stereotype proudly. This article describes that fundamental role Outdoor School plays in our community.

But now, not all school districts have funding for their students to have these experiences. A new movement, Outdoor School for All, aims to get every sixth grade student in Oregon back out for a full week of Outdoor School. As this program started with government funding, a sustainable solution to get all of our kids outside now relies on government funding again. So in order to help secure House Bill 2648 and Senate Bill 439, we need letters to explain why Outdoor School matters. You are welcome to use this letter generator to write one too!

Here is how Outdoor School ignited my passion as a scientist:

Dear Lawmakers,

Science is my path to make a difference. I discovered this passion in the pouring rain beneath a forest of big-leaf maples covered in moss with five inquisitive sixth graders. We were testing the dissolved oxygen of the Salmon River when Rosa’s eyes lit up and she exclaimed, “I never knew I could learn all this!” When this student realized she was capable of understanding the natural world and cared about the world she discovered—this same moment I knew how I would spend my life. I built community, excited students about learning, and discovered my talents in creating joy for ecology. My exposure to science while volunteering as a student leader for the MESD Outdoor School program gave me the momentum, passion, and confidence to become a woman in science.

There are a few reasons Outdoor School is a powerful way for students to learn. First, the Outdoor School textbook “chapters”: plants, animals, soil and water, are written in words every child can understand by touching, seeing, and experiencing each one in order through a full day dedicated to experientially studying each area. Second, throughout one school week at Outdoor School, students have enough time to process each day of field study and make connections between them. I have seen countless students in awe of how interconnected the plants, animals, soil and water really are. I feel it too. Because of this, I live with more connection to the earth, more affinity for discovery, and more passion for sharing this awe with the global community.

I finally understood why this feeling of awe can be so powerful when Dr. Kelly Swing, the director of the Tiputini Biodiversity Station in Ecuador, quoted an Amazonian tribe leader in a presentation to visiting students:

“We only know what we see; we only love what we know; we only care about what we love”. This has become my personal mission statement.

Some days I feel powerless. Numbers can be defeating—statistics on global carbon emissions, deforestation rates, biodiversity loss, increased poverty, inequality in human rights, and school shootings lead me to question whether I can have a positive impact. Science gives me hope; through science more people have a reason to care. My goal is to create research to discover new results, my findings will allow deeper understanding, and through understanding my work will facilitate an affinity for ecology. Through practice I know I have the power to connect as a science instructor and I have the power to connect across cultural boundaries—both of these skills started at Outdoor School. Of course I am still refining the art of connecting people from many different backgrounds to science, but luckily science inquiry is a task that has brought me joy ever since I learned how to teach at Outdoor School.

Teaching others to wonder and think like a scientist has arisen from my own process in asking questions about the natural world. By asking questions I gained many answers and many more questions. I have learned to measure the success of my scientific endeavors by the questions they lead me to next. Many mentors have shaped the way I frame my curiosity. This also what makes Outdoor School successful: mentors. High school students act as role models while presenting science to sixth graders, all while learning from their own mentors, the Outdoor School staff, how to be a leader and their best selves. I am extremely grateful for my mentors from Outdoor School that helped me build confidence and joy for life. I carried this confidence with me to study biology in college and eventually returned to work at Outdoor School to give back.

While I worked as a Field Instructor, I struggled for a long time to develop a curriculum that fully encapsulated all of the desired concepts, to be sure each student was able to feel that awe when they understand how everything connects. But then I realized from watching my high school volunteers engaging their students in measuring the dissolved oxygen of the Salmon River, that community was the secret ingredient generating passion for science. In moments of discovery and connection to community: that is where change happens.

Thank you very much for your time and consideration. Please give all kids in Oregon the chance to experience Outdoor School. I ask that you move the Outdoor School Legislation, HB 2648 and SB 439, out of committee with funding in order to be voted on and passed into law.

Sincerely,

Adrienne Godschalx

How to Catch a Bee

During my days as a summer camp unit director, one of my campers brought me a flower. When I looked closer, I realized this 11-year-old was not interested in the flower, but the bee and spider on top of the flower, head to head. I assumed they were fighting, but they were both pretty still, and it dawned on me that the bee was a goner, locked in the “jaws” of the spider, whom I figured had won the fight. I was still wrong, and the reality of this interaction is even cooler than I had imagined:

The spider hunts by hiding in flowers that attract their prey, the bees.

I posted my spider-bee-flower pic on Instagram recently, which received more interest than I had expected. I even had comments asking about the evolution of this flower-sitting ambush spider, so I looked it up, and I stumbled upon a cool chemical ecology story.

The first thing I learned is that, when given a choice, both the bees and this group of spiders, crab spiders, pick the same flowers. By covering the flower with saran-wrap and watching the spiders’ flower choice change, scientists were able to figure out that spiders are choosing their flowers by following chemical signals in the air, aka smells. This means these spiders are adapted to smelling out flowers that are more likely to attract their dinner.

Do bees fall for this trap? Bees not only fall for this ambush, but are more attracted to flowers with spiders than to safe, spider-free flowers.  Why would a bee fly closer to a purple flower that has a white, hungry spider in the middle?

Clearly, bees see differently from us. As I was perfecting my Instagram post, I was struck by my black and white Instagram filter, which showed the flower and spider as same shade of white (Figure 1). Even without extensive training in bee sensory biology, I figured there must be some sort of visual trick at play.

Figure 1. Screenshot of my Instagram post with 100% of the color saturation removed.

Too bad there is no UV filter on insta, because bees can see ultraviolet. Flowers take advantage of the bees’ visible spectrum in UV and often attract bees with target-like patterns, using dark UV spots in the middle. Darker UV target patterns can mean more pollination, so this trait is selected for in both flowers and bees.

So why are bees attracted to the crab spider flowers? Crab spiders have a layer of transparent cells covering spider skin cells that can change color! There are a few types of this pigment- the ommochrome pigment, which either allows spiders to or yellowish to red, or allows white spiders to have UV fluorescent patterns. With a UV pattern on their backs, flowers with spiders look like an extra dark flower target and attract bees more effectively than flowers without spiders.

Of course, natural selection goes both ways. Native bees in Australia fly close to, but can recognize and veer away from native crab spiders, whereas introduced honeybees have not adapted to recognize this danger.

Plants interact with insects and their predators. Scientists use the term “tritrophic interactions” to describe three trophic levels, or links in the food chain, interacting and affecting one another. As my thrilled camper and curious Instagram “fans” could pick up on, tritrophic interactions are fascinating! From an applied science perspective, knowing the intricacies of tritrophic interactions is essential to fully understand the side effects of potential global solutions in food security, and pest management, and conserving biodiversity.

-A

Note: All the papers I cite in this post are by Dr. Astrid M. Heiling, who has many other fantastic papers. Check her work out!

Incoming call: National Science Foundation

I knew grad school was about publish or perish—and in the meantime—secure some funding. What I did not know was that this daunting, impersonal process would contain happy instances of genuine personal interaction, like when a program officer called me to award funding over the phone.

The National Science Foundation is a government funded organization that supports a large chunk of federally-funded basic science research. Virtually every incoming graduate student  is encouraged to apply for the Graduate Research Fellowship Program, referred to as the GRFP on the streets. Part of the science lingo I had to learn in my first year of graduate school were all of the grant acronyms. The DDIG is the Doctoral Dissertation Improvement Grant, which funds research that allows PhD Candidates to take their work to the next level.

I had almost forgotten about my NSF DDIG grant proposal since I submitted it in October. Five months between deadline and verdict is a normal timeline for grants, which is both frustrating and a saving grace. The grace comes in taking some time apart from my own writing long enough to forget about it, lessening the blow to my writing ego when the funding judgement day arrives.

This time judgement day came in the middle of my commute to work as I was singing along to my guilty pleasure cd from a musical I saw in New York: If/Then. Not only am I obsessed with Idina Menzel, but I also love the challenge in this story about wondering “what if” along with every decision and life event, big or small.

And then Doug called.

It wasn’t completely out of the blue, since he sent me an email to inform me he wanted to call about my proposal, but the email sent me into a panic that something was missing or I selected the wrong category in the online application and my proposal was rejected without review. I was prepared to defend why this grant would improve my dissertation when Doug said, “Congratulations!” As he walked me through the logistics, I could not get over the fact that a program officer from the National Science Foundation called me instead of informing me mechanically by email. Hearing someone’s voice and knowing their name felt personal and genuine. Classy move, Doug.

-A

Note: Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

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)

Armed and Delicious.

Go to your spice rack, make a kale smoothie, have a cup of coffee. Just about everything we use to add flavor to our lives comes from a co-evolutionary battle between an herbivore and a plant protecting its leaves.

That bite on your tongue from an arugula salad? The sulfur-containing cyanide molecules you taste are the result of glucosinolates, a characteristic defense of the mustard plant family. Mustard plants—e.g. horseradish, wasabi, mustard—all use this metabolic pathway because the burning sensation, which many people enjoy with oysters, actually works as an effective anti-herbivore toxic defense. When bugs break open cells, the enzyme myrosinase cuts a precursor to release nitriles, isothiocyanates, and other various bioactive toxic compounds. Plants in a population that are slightly more toxic survive the constant herbivore attack better and can pass on their genes to the next generation. Ah, bittersweet natural selection.

How do we know it is the bugs that put the pressure on? This paper (also summarized in a great article here) swapped mustard plants from Colorado and Montana, and found that not only did the unique spice of each plant stay consistent, but bugs preferred the visiting treat—plants that did not adapt to the local suite of herbivores. The difference in plant survival in this case is an example of local adaptation, all starting from bugs preferring the new mustard spice.

Just like these bugs and everything else in nature, we choose what we eat based on the flavors we like and what won’t kill us.

So why do we intentionally eat so many compounds plants use to make feeding difficult? Often these same toxins are essential for nutrition. The darkest green vegetables, pungent garlic, soothing mint—all play a health benefit role because of the energy plants put into making defense compounds. Bioactive toxins in low doses continue to do their toxic, bad-self thing: the alkaloid caffeine in your coffee stimulates the nervous system, the indole-3-carbinole in your kale salad degrades excess hormones that can lead to cancer, and the terpenes in oak barrel-aged wine rich in phenolic tannins can prevent carcinogens from binding to DNA and reduce the risk of harmful blood clots. The underlying theme here is that many toxins are reactive, for better or for worse.

Disclaimer: Some plant defenses are toxic to humans in high concentrations, and some plants are just plain poisonous at any dose. Don’t start eating everything toxic. Instead, appreciate the nutrients plants invest in creating highly reactive compounds in order to protect themselves, as well as the coevolutionary arms race that made plants with these exciting products succeed.

Wings on Fire

I had always dreamed of going to the Amazon. The rainforest was a dream that breathed new life into me the way it breathes oxygen into the planet. As indescribable as the awe that comes from being amongst such biodiversity may be, the rainforest enchanted me in the movement of a toucan awkwardly wielding its beak, and in the flapping of wings on fire in the sunset as the faithful scarlet macaw streaks across the sky in its squeaky calling out to all below. Some moments brought forth vulnerabilities- the surprise of a snake’s delicate flicker of its tongue interrupting our gaze, and some brought forth grace, such as meeting the long-dreaded tarantula and experiencing not fear, but its majesty. Walls of rain sing in the rainforest upon giant sheets of leaves and dance on the surface of the turbid river. There is promise in the sunrise through the canopy mist, and in the sigh of achievement in the last orange glows on emergent branches, awaiting the stars and tree frog songs. I believe in this feeling of awe, and in its power.  Because of this, I live with more connection to the earth, more affinity for discovery, and more passion for sharing this awe with the global community. Dr. Kelly Swing, the director of the research station, quoted an Amazonian tribe leader in a presentation to visiting students, “We only know what we see; we only love what we know; we only care about what we love”. This has become my personal mission statement.

Some days I feel powerless. Numbers can be defeating—statistics on global carbon emissions, deforestation rates, biodiversity loss, increased poverty, inequality in human rights, and school shootings lead me to question whether I can have a positive impact. Science gives me hope; through science more people have a reason to care. My goal is to create research to discover new results, my findings will allow deeper understanding, and through understanding my work will facilitate an affinity for ecology. Through practice I know I have the power to connect as a science instructor and I have the power to connect across cultural boundaries. Of course I am still refining the art of connecting people from many different backgrounds to science, but luckily science inquiry is a task that always brings me joy.

-A

Velcro: a catchy defense.

My first claim to fame in grad school was about tiny hook-shaped plant hairs.

Exciting right? You’d be surprised how a simple observation leads to better understanding the big picture. Here is the happy hour version of my first publication that helped us understand how plants use different combinations of defenses to protect their leaves from being eaten.

First, why would plants have more than one defense? Remember, plants are unlike many organisms because they make food for themselves via photosynthesis. All of the non-photosynthesizing critters also need to eat, and they do so in many different ways. Caterpillars, aphids, and fungi all see leaves as an appetizing snack, so plants respond to the chewing, phloem-sucking, and pathogen infections with an arsenal of defenses.

Releasing toxic cyanide is one way to deter picnickers. The more bugs munch and rupture plant cells, the more cell contents mix, and enzymes previously separated from precursors start producing hydrogen cyanide.

Cyanogenesis- Releasing toxic cyanide from injured cells, chemical defense.

So with such a toxic defense, why would any plant need more protection? When aphids use their stylet like a straw to pierce and suck sugar-water out of the plant’s bloodstream, they avoid the mechanism that releases cyanide. Conveniently, these same plants with unfulfilled cyanogenic potential also have tiny hooked hairs, which likely act as Velcro, trapping small phloem-sucking bugs.

Trichomes- Plant hairs, mechanical defense.

What about diseases? Fungal pathogens can also consume leaves, forming a lesion. How far the infection spreads depends on the plant’s anti-fungal defenses. Polyphenol oxidases form sheets of proteins that act as walls to quarantine the infected cells.

Polyphenol oxidases- antifungal, chemical defense, comes from the plant when needed (direct, inducible defense).

Firm edges around the outside of a lesion indicates such a defense is working to stop the infection from spreading. When this process is lacking or interrupted, the infection appears faint, and spreads into the leaf’s veins. This is how my advisor and his team noticed the physiological tradeoff in lima bean plants between polyphenol oxidases and cyanogenesis. Cyanide is toxic because it interrupts many enzymes that allow our mitochondria powerhouses to function. Releasing cyanide also breaks down other enzymatic functions, such as this anti-fungal defense compound. So plants with lots of cyanide are vulnerable to fungi, while plants with less cyanide are vulnerable to herbivore attack, but are protected against disease. Here we begin to see relationships among these traits, and in this case, two defenses tradeoff.

Why are tradeoffs so fascinating to scientists? Because tradeoffs limit adaptation.

Plant defense is widely considered to limit adaptations in growth or reproductive traits because defense compounds cost the plant resources and energy. The solution many plants find to balance this dilemma is to use varying defense strategies and call for help. Predators scare off or attack the plant’s enemies by following plant cues or rewards. Nectar is typically associated with pollination, but many plants also produce extrafloral nectar: droplets of nectar designed to attract ants and other predatory bugs.

Extrafloral nectar- sugary liquid to attract carnivorous bodyguards (usually ants), indirect defense.

Plants under attack can turn up the production of volatile organic compounds, which serve many functions, one of which is attracting wasps that parasitize and kill the source of damage by laying eggs in the herbivore.

Volatile organic compounds (VOCs)- Chemical cues floating in the air to attract parasitoid wasps, indirect defense.

Traits that show up together in the same plant form a defense syndrome. Syndromes tell us which combinations of defenses help plants survive better, and which adaptations work best in concert. I assembled the defense syndromes for wild and cultivated lima beans to see how the tiny hook-shaped hairs fall into the big plant-protection picture. Two patterns emerged: 1. Plants with many trichomes also have lots of cyanide, and 2. Plants with low cyanide and fewer trichomes produce more extrafloral nectar and VOCs.

Why does this matter?

The tradeoff between direct chemical defense and indirect defense is well complemented by mechanical defense in the existing defense syndromes. As a plant, if your strategy is to be toxic, but some bugs can avoid the toxic effects, it makes sense to have a Velcro-like surface so it is harder to move around or even get to the plant to feed. If your strategy is to call for help, having a tricky surface to navigate hinders the protective ability of the predators that come to the rescue.

Therefore, chemical and mechanical defenses co-vary in lima bean, which ultimately tells us how different kinds of defenses work together to minimize munching.

-A

Santa Claus is Comin’ to Town!

In the spirit of Christmas, a time for giving, I find it fascinating that one concept perplexing many scientists is the number of species that help each other. This is called a mutualism in science speak, and is confusing to many scientists because the underlying rules of natural selection (Darwin, 1859) intuitively work against spending energy or valuable resources helping others. Remember, fitness= grow and reproduce (although this kind of fitness is also fun). Any trait involved in spending the currency on an unrelated organism that would otherwise go towards kids theoretically would not last for many generations (because it takes having kids to make a new generation with those traits). But mutualistic traits do last, even when other organisms evolve ways to cheat and take more than they provide, further baffling evolutionary ecologists.

Which is why I think this paper is so cool.

The scientists used a creative strategy to assess how plants deal with the extra loss of sugars without any return of nitrogen when the symbiotic bacteria in their root nodules cheat. The creative part is forcing bacteria to cheat: rhizobia, which take the inaccessible, triple-bonded nitrogen from the air and turn it into a useful, organic molecule for the plant are not able to provide this service when there is no nitrogen in the air! Dr. E. Toby Kiers and her team kicked out all of the nitrogen by flooding chambers with roots and nodules with oxygen, 20% (rhizobia need oxygen too), and argon, 80% – a stable gas that is heavier than nitrogen.

Plants with “cheating” rhizobia on their roots cut off the oxygen supply to those nodules!

This concept of punishing cheaters (aka host sanctioning) to maintain a fitness benefit from the relationship is a huge help in solving the evolutionary questions about two-way beneficial relationships (mutualisms!) in nature.

It’s kind of like how Santa keeps you on your best behavior so you don’t get coal in your stocking.

Merry Christmas (or whatever you celebrate)!

-A