How kangaroo gut bacteria could help cut a potent source of greenhouse gas emissions

Methane is a greenhouse gas that is roughly 25 times more powerful than carbon dioxide at trapping heat in the atmosphere, making it a key target of global efforts to fight climate change. Dairy cows and beef cattle are a significant source of methane, which is released as a byproduct of food digestion in the stomach of cows and other hoofed animals. Kangaroos, like cows, also have microbes in their gut which aid in digesting plant material. But these microbes release acetic acid instead of methane. Scientists at Washington State University collected gut bacteria from zoo kangaroos, and then introduced cultures of the bacteria into a solution mimicking a cow’s stomach. The bacteria quickly flourished and replaced the community of methane-producing microbes. Birgitte Ahring is a professor in the Bioproducts, Sciences and Engineering Laboratory at Washington State University. She joins us to talk about the research, which is described in a paper recently published in the journal Biocatalysis and Agricultural Biotechnology, and how it could help the agriculture sector curb a potent greenhouse gas.

This transcript was created by a computer and edited by a volunteer.

Dave Miller:  This is Think Out Loud on OPB. I’m Dave Miller. Methane is a potent greenhouse gas. It’s roughly 25 times more powerful at trapping heat in the atmosphere than CO2 is. Dairy cows and beef cattle are a big source of that methane. But scientists at Washington State University say they may have found a surprising way to reduce methane emissions from dairy farms or feedlots. They used bacteria from the guts of baby kangaroos. Birgitte Ahring is a professor at the Washington State University Tri-Cities campus in Richland. She joins us now. Welcome to Think Out Loud.

Birgitte Ahring:  Thank you.

Miller:  So I want to start with the reason that you embarked on this research in the first place. Can you just remind us why methane is such a problem as a greenhouse gas?

Ahring:  It’s a problem for the climate. It’s a problem for our ideas on how we can actually mitigate these problems. And it is a major problem also for the fact that beef is a major source of nutrition for a lot of people and also it’s very loved in the United States. So of course, it is very obvious that here you have something that is a major problem, is giving us up to 18% of our greenhouse gasses. And we have to do something to it. And if we can do it, but still have beef production, it would be beneficial for a lot of partners.

Miller:  So when you said 18%, that’s the methane in the atmosphere that comes from animal agriculture, almost 20% is from methane, say, from dairy cows or beef cattle?

Ahring:  Yes, it is from animals that have that very specific type of stomach system where they have what’s called a rumen. That’s a big balloon-like part of the whole gut system.

Miller:  Just to focus on that one animal, cause it seems like [cows are] most likely culprit for this methane. Why is it that they are so likely to burp or fart methane?

Ahring:  It has actually to do exactly with the rumen system, that big balloon stomach where they actually have an amazing type of culture. And that culture breaks down even complex organic material. And it breaks it down by a concerted action of a lot of these microbes. They work together, this concerted action, and in the last part of that process, they produce precursors for microbes that produce methane. And that precursor is gasses, compounds like hydrogen and CO2.

Miller:  What’s in this for cows? I mean, do they benefit from the release of this methane in some way? Obviously, we are not benefiting globally from all this methane. But is there a reason biologically for cows to actually get rid of gasses this way?

Ahring:  It’s a very good question because to be honest, these are systems that have developed over a lot of time and they are very, very stable. So that benefit is that they actually have a good, very effective process to degrade organic material. And at the same time, they have stability in this system. And if they don’t remove that hydrogen CO2 that is produced as part of the process, then they actually can have upset stomach and they can have problems. And that is a very important part to understand that actually the cow has this process because it makes sense for them.

Miller:  In other words, the microbes that turned the hydrogen and CO2 into methane, there is a benefit for the cows, even as it is causing serious problems for all of us together. There have been different kinds of attempts to reduce methane produced by cows, including by changing their diet. How effective is that?

Ahring:  There’s actually several types of compounds you can use to actually prevent the methane producing microbes from being active. And they are both something that could be a specific type of algae type that has been described. But there’s also chemicals, like an antibiotic, that directly inhibit the methanogenic microbes. And they are very efficient. But at the same time, the methanogens, as microbes in general, they’re very good at adapting to these situations. So you would see an effect, but after a while, you begin to see that they are adapting and they actually, again, begin to produce methane. The cow again begins to produce methane.

Miller:  If I understand correctly, that’s where your research took off saying that the existing ways to reduce methane in livestock, they may work. But they’re short acting and the methanogens, these microbes that create the methane, kick back into gear at some point. So where did you start in terms of your idea of finding a new way to reduce methane production?

Ahring:  So the first thing I did was to examine what other microbes do we have that could substitute the methanogens? And a very obvious group was what’s called homoacetogens. And they produce acetic acid from hydrogen CO2 instead of producing methane from hydrogen CO2. And why would that be such a good idea? Because acetic acid is actually what the rumen produces. It’s a big part of what it produces and that goes into the bloodstream of the animal and is what actually the animal is used for its energy generation but also for making more meat. So it could be beneficial for both the animal but also for the production of livestocks in general.

Miller:  I’m used to seeing acetic acid, say, on bottles of vinegar that say 4-6% acetic acid. So you’re saying that this acid in the stomachs of cows, actually helps cows grow?

Ahring:  It is basically what it does. It takes the organic material, let’s say it is hay, for instance, or corn or whatever, and it breaks it down and the end product of it is different parts of these small organic acids and some other things. So these small organic acids are extremely important for the function of the rumen. And so therefore, if we actually could just substitute the methanogens with somebody who produced something that was beneficial, that was my idea. That it would be a really good idea.

Miller:  And that somebody, spoiler alert, happens to live in the stomachs of kangaroos?

Ahring:  The interesting thing about this is that you have homoacetogens which has been described, from all kinds of systems, including the cow. But when you take these strains and you try to actually substitute the methanogens, they’re not competitive with the methanogens.

Miller:  So if I understand correctly, you’re saying that cows also have been found to have some of these bacteria that, instead of creating methane, create acetic acid, which is what you want to do. But they don’t do as well in a cow stomach as the methane producing microbes do?

Ahring:  Exactly. The methane producing microbes has a competitive advantage. They’re better in using the hydrogen and Co2.

Miller:  And so when do the kangaroos jump into this conversation?

Ahring:  So what I did was, after testing a number of these known homoacetogens, I actually started reading about different types of systems and tried to see if I could find the system that was actually based on homoacetogens instead of based on methanogens. And then I actually found that in the foregut of kangaroos. There has been, of course, Australian studies that actually found kangaroos that did not produce any methane. So then the next step was where can we find some kangaroos?

Miller:  Right, because you’re in the Tri-cities. So what is the answer? They’re not just jumping around there?

Ahring:  They’re actually in Washington State, we found that there were two petting suits that had kangaroos and one of them was pretty close to Seattle. So we went there or my students went there and they sampled feces from these kangaroos. So they sampled from a number of adult kangaroos and they also got some from a baby kangaroo. And the interesting thing was that we took it to the lab and we grew it on hydrogen CO2. And what showed up was that for the baby kangaroo, we did not have any methane production produced. But for the adults, we actually saw that they had methane. Besides, they also had some acetic acid production, but they still had methane.

Miller:  How did you explain that? What was special, do you think, about the babies? What was different, I should say, about the adults?

Ahring:  I think they might be born without methanogens and they haven’t found their way maybe into the system. Or maybe the kangaroos that are in a petting zoo are different from out in Australia. Because it was previously described that they had found kangaroos in Australia that did not produce methane.

Miller:  So the next thing that you did, if I understand this research correctly, is you developed, or took a strain, of the acetic acid producing bacteria and you put it into a simulator you have that mimics the actions of a cow stomach. What did you find?

Ahring:  It was very interesting because the first thing we did was to inhibit the methanogens in the culture. And very interestingly, we found that actually that kangaroo culture took over the function of the methanogens and continuously made acetic acid instead of methane, for up to three months. And that was an extremely interesting observation because we have tested exactly the same system with a large number of these homoacetogens and knew even the ones from the cows didn’t work. So then suddenly we actually saw that these baby kangaroos had actually a culture that is much better suited for the system than actually the ones that we have previously known.

Miller:  Is the next step to put these baby kangaroo bacteria into the stomachs of live cows?

Ahring:  Yes, that is our next step, to do a live study. And at Washington State University, we have an animal nutrition department and an animal nutrition department in Pullman that has what’s called fistulated cows. That’s cows that has actually like a stopper in the stomach you can take off and then you can actually add things directly into this big balloon rumen. And that is the next part that we are working with the department.

Miller:  If that works, in that next step of the experiment, you find that you can actually reduce the amount of methane produced in the guts of cows, what is the dream application here? I mean, can you describe the way this might eventually work at feedlots or dairies?

Ahring:  I think that with this culture, we might be able to. That’s what I’m hoping we will demonstrate in live animals. We might be able to show that we can actually reduce significantly or even eliminate, at least for a long period of time, methane production from these animals. If we can do that, it will be a major, major breakthrough.

And even if we have, let’s say, to help the rumen to prevent this methane again by adding an inhibitor from time to time, let’s say every three months. Even if we have to do that compared to having to add these additives, that are extremely expensive on a daily basis, that would really, really matter for the economy of this. And at the same time, if we only add inhibitors of methanogens a few times a year, we wouldn’t see the same adaptation. And that problem we have seen previously with a number of these additives.

Miller:  I’m curious just given the overall carbon footprint of animal agriculture, even without methane creation, how do you feel about research that could serve to further livestock production around the world?

Ahring:  I’m working on the problems that are here and now. And for me, this is obviously a good solution that could help. But it doesn’t mean that I don’t work on a lot of other problems in the world to do something for the climate. There are a lot of different things we can do. And we, in microbe, are very very focused on finding solutions that can help the world.

Miller: Birgitte Ahring, thanks very much for joining us today.

Ahring: Thank you very much.

Miller: Birgitte Ahring is a professor in Washington State University’s Tri Cities campus in Richland. She joined us to talk about her group’s research looking into the bacteria found in baby kangaroos and with the hope of reducing methane emissions from livestock.

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