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Can Probiotic Bacteria Save An Endangered Frog?

I saw a ghost at the Vancouver Aquarium last summer. I was walking out of a room overlooking the main shark tank when I saw something in a glass cage embedded in the wall, something small, black and yellow. I mean Black and Yellow—colours so intense that you almost expect to turn the creature over and find a country of origin embossed on its underside. It was a Panamanian golden frog, and it is extinct in the wild. It only survives in zoos and aquariums. It is an ecological phantom, a ghost of nature.

Several factors took the frog to the edge of oblivion but the one that landed the most punishing blows was a chytrid fungus called Batrachochytrium dendrobatidis, or Bd for short. It is the same grim antagonist that has severely reaped the populations of some 200 amphibians and seems to be working its way through the rest. It is catholic in its choice of hosts and apocalyptic in its effects. The Panamanian golden frog is just one of its victims.

Conservationists have been incredibly successful at breeding the frog in captivity. But if they release these animals back into their native habitat, where Bd still persists, who’s to say they wouldn’t just die? Their ark is full, but there’s no Mount Ararat in sight.

In 2006, a team of researchers stumbled across a possible solution. They found that a few amphibians, including two salamanders and the mountain yellow-legged frogs, naturally carry a bacterium called Janthinobacterium lividum that stopped Bd from growing. It was an anti-Bd probiotic, a microbial shield that turned frogs into resistant fungus-fighters. And when the team applied the bacterium to yellow-legged frogs that didn’t already have it, those individuals also became resistant.

Could J.lividum protect other frogs too? To find out, Matthew Becker from James Madison University, who was part of the original team, teamed up with Brian Gratwicke from the Smithsonian Conservation Biology Institute, who had a group of lab-bred golden frogs. They soaked the frogs in a J.lividum bath and challenged them with Bd. If the approach worked and the frogs survived, perhaps they could be released into the wild, cloaked in their living armour.

It didn’t work. The probiotic microbe didn’t persist on the frogs’ skins, and it did nothing to save them from the fungus. “We thought maybe it wasn’t a good fit,” says Becker. “This bacterium was from California and these frogs are from Panama.” Perhaps frogs from different parts of their carry their own particular probiotic microbes that have adapted to thrive on their skins. If Becker was going to find a probiotic that could protect the golden frogs, he would need to go to Panama.

He went in 2011 and spent a week surveying the skin bacteria of local frogs, focusing on species that were as closely related to the golden frog as possible. Over a week, he collected 450 samples and found several microbes that stopped Bd from growing, at least in lab tests. He focused on four of these, and applied them to captive golden frogs, to see whether they could then survive a bout with Bd.

They couldn’t. On average, the treated frogs survived no longer than untreated ones. And once again, “nothing persisted,” says Becker. “Their existing microbial community didn’t even shift in response to [the new microbes].”

The same problem plagues human probiotics. When they’re swallowed, they don’t take up permanent residence in the gut and they don’t affect the make-up of the local bacteria communities (although they do seem to change the activity of certain genes). After all, a typical yoghurt contains several billion bacteria, whereas our gut contains tens of trillions. It’s like a raindrop falling into a lake. Perhaps this explains why probiotics can help with a small number of diseases, like diarrhoea caused by infections, but have largely failed to live up to the hype that surrounds them.

With the frogs, Becker wonders if he applied too many microbes rather than too few. “I think we may have activated the frogs’ immune systems and prevented the probiotics from establishing,” he says. Alternatively, we know that even closely related animal species can host distinctive microbiomes, so what persists on one frog may just not thrive on another. It’s also possible that the skins of captive golden frogs are already colonised by microbes that stop the bacteria of their former Panamanian neighbours from colonising.

In the midst of their disappointment, the team found a silver lining. Five of the frogs managed to clear the fungus on their own. “That’s pretty unheard of in golden frogs,” says Becker. When he focused on these animals, he found that they differed from those that died, in the groups of bacteria on their skin and the chemicals that those bacteria produced.

What are these microbes? Do they actually protect against Bd or are they indicators of some inherent resistance, perhaps some immune genes that both resist the fungus and select for specific skin microbes? If they do protect against Bd, would they do so in the wild? Are they part of a golden frog’s natural repertoire, or did they only start colonising these animals in captivity? The team is now working to answer these questions. Becker is sampling 200 of golden frogs at Maryland Zoo in Baltimore to see if he can find these potentially protective communities, and then apply them to other frogs to see if they also become Bd-resistant.

The concept of using probiotics to protect amphibians (and perhaps other animals at risk from widespread epidemics, like bats) makes sense. Many animals, from humans to corals, carry skin microbes that protect us from incursions by disease-causing species, by secreting natural antibiotics, mobilising our immune systems, and simply filling up niches that the invaders might otherwise exploit.

But our own experience with probiotics, and Becker’s frog experiments, tell us that deploying these seemingly beneficial bacteria is easier said (and marketed) than done. Probiotics may help to save the frogs but it’s unlikely that we’ll see a one-size-fits-all solution, and the same could be said for the use of microbes in human medicine.

*****

There will be more about frogs and conservation probiotics in my book, I Contain Multitudes, out next year.

Reference: Becker, Walke, Cikanek, Savage, Mattheus, Santiago, Minibiole, Harris, Belden & Gratwicke. 2015. Composition of symbiotic bacteria predicts survival in Panamanian golden frogs infected with a lethal fungus. Proc Roy Soc B http://dx.doi.org/10.1098/rspb.2014.2881

More on Bd:

Update: The post originally said that the 200 golden frogs that will feature in upcoming experiments were at the Smithsonian; they actually live at Maryland Zoo in Baltimore.

11 thoughts on “Can Probiotic Bacteria Save An Endangered Frog?

  1. I love you and all, but I have to admit I cringed slightly at the “ghost of nature” metaphor. The common attitude that only survival in a species original, outdoor environment constitutes “true” survival has always left a bad taste in my mouth. I feel like we’re long past the point where we should abandon the pretense that we can (or even necessarily must) focus on preserving things exactly as they were before we screwed them all up.

    If we’re the ones that destroy natural habitats, is it not perfectly fair for their species to go on surviving even in habitats we newly provide for them?

    There are many species that only continue to exist in captivity; the axolotl may be one of them within our lifetimes, there’s a cave roach narrowly rescued by hobbyists, and of course many frogs now. If we could accept that maybe existence at all is good enough, we might preserve far more.

  2. Jonathan, first of all we’re not “providing new habitats” for these animals – the frogs kept in captivity for breeding programs live in small glass aquariums, largely unable to act out their innate instincts. Secondly, many species of frogs were made extinct in the wild because researchers removed them from their habitats in case they were susceptible to the fungus. Because the researchers know little about the natural history of these species, many frogs have died in these captive breeding programs, sometimes starving to death. Finally, we didn’t destroy their native habitat. Chytrid spread through Central America on the backs of other native frog species that are resistant to the fungus (and thus act as carriers). Maybe the fact that these frogs still exist is good enough for you, but it’s not good enough for the frogs.

  3. I was very interested in the following:
    “The same problem plagues human probiotics. When they’re swallowed, they don’t take up permanent residence in the gut and they don’t affect the make-up of the local bacteria communities (although they do seem to change the activity of certain genes). After all, a typical yoghurt contains several billion bacteria, whereas our gut contains tens of trillions. It’s like a raindrop falling into a lake. Perhaps this explains why probiotics can help with a small number of diseases, like diarrhoea caused by infections, but have largely failed to live up to the hype that surrounds them.”

    I am currently taking VSL3 (at a cost of over £1/day) to deal with IBS. They claim to provide 450 billion bacteria including Streptococcus thermophilus, bifidobacteria B.logum, B.breve, B.infantis, Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus paracasei, Lactobacillus delbrueckil

    Given your extensive research into the microbiome – can’t wait for I Contain Multitudes – I would welcome your thoughts on whether this is just an expensive raindrop in a lake.

  4. This is good news for captive breeding facilities, since it makes contamination by the fungus less likely. But it is hard to see how the bacteria would pass from one generation to the next in the wild, and without that, it won’t help the wild frogs beyond the first generation. Are there any ideas about how to solve that problem?

  5. If the zoospore for Bd travels in water, why not find something that will kill it and use it in specific places frogs live? These areas can become protected reserves. It might be worth a try?

  6. Kara, I’m sorry to say you’re still demonstrating an attitude I think is only slowing conservation efforts and needs to be dropped.

    If a species is alive, then it has survived. If a species is reproducing, then it is surviving in a habitat, whether it’s man-made or otherwise. The sooner we accept that, the safer some species will be. Sometimes we allow organisms to die off in the wild that could have easily been preserved in captivity or even transplanted.

    That’s a big thing too – some conservationists are only now beginning to propose transplantation of some species to new wild environments and the rest of the community acts like it’s heresy. Their potential to become “pests” seems like a pretty reasonable risk when we’ve already shuffled around thousands of other species by pure accident and made many environments impossible to repair.

  7. I am very grateful that some people try to help the species in danger of extintion. But if you you help them changing something, like resistence to the Bd in the golden frogs and you put them to their ecosystem, the ecosystem is going to change because the Bd can adaptate to the resistance and it can start killing again the frogs or it is going to atack a new animal and with that this animal is going to be in danger like the golden frogs are now.
    So I want to let you know that always it sounds good but you must think in the consequences of the future if you change somthing in the ecosystem and in the food chain.

  8. Jonathan, the purpose of building the amphibian ark was to temporarily house and breed species while a cure was found, and then release them into the wild. There is no conservation reason to keep species in captivity if it is not for the purposes of a breeding program with the eventual hope of reintroduction into the wild. What you are proposing is just a zoo and animals kept in zoos without a reintroduction plan evolve to be a shadow of their former selves—they lose their social cultures (yes, animals have cultures) and they become genetically adapted to captivity.

    The purpose of conservation biology is NOT to preserve species in isolation—it is to preserve functioning ecosystems. Putting a species in a zoo is not conservation. And considering that I am a conservation biologist, I have enough scientific knowledge and training to know that working towards saving ecosystems with their biota intact is not slowing conservation efforts. However, your distorted view of how ecology and biology works certainly is damaging to conservation because attitudes like yours assume that we can just throw animals into captivity and everything will be fine. If you enjoy clean water, clean air, a livable climate and food to eat, then you might want to reconsider your ideas about conservation.

    PS – If you want to keep insisting that saving species in isolation is a good thing, then please come up with a new word for it because it does not fit the definition of conservation. Conservation is the preservation of biodiversity, ecosystems and interactions between organisms. That can’t be done in a zoo, which is why conservationists only use zoos as a temporary last resort.

  9. While the exact numbers are hard to determine, it is thought that since 1980 approximately 6-8 mammals have become exist, including species such as the Western Black Rhinoceros and Pyrenean Ibex. Due to the irreversible nature of extinction, these headline-making losses are tragic. However, in the same amount of time it is estimated that 122 amphibian species, including a considerable amount of frog species, have become extinct. Therefore, after reading this article, I can’t help wonder why is it that the conservation of these species is not given the same mainstream media coverage. The Batrachochytrium dendrobatidis chytrid fungus has been known to spread from country to country as a result of human interventions of removing amphibians from their native environments and releasing them in new populations. Would it not be wise to promote awareness and enforce stricter pet/ exotic animal/zoo trades to ensure the chytrid fungus does not spread? Amphibians that do need to be shipped to other countries should undergo proper disease testing and quarantine procedures. In my opinion, combating the origin of the problem as opposed to the symptoms may be a more effective way to curb future extinctions. With this said however, I find work of scientists such as Matthew Becker incredibly admirable. As mainstream media is usually focused with conservation of large mammals, it is refreshing to read that there are groups of people working just as hard to protect smaller, less heard of species. I believe it is of vital importance these initiatives are given the same opportunities and funding to enable conservation of Earth’s ecosystems, as opposed to solely individual species. After all, the conservation of an individual species will have no meaning if the species does not have a stable and balanced ecosystem in which to thrive.

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  10. It is appalling to think about a few specimens of a once thriving species now breeding only in captivity while their conspecifics die in the wild. Is it better to keep the species alive in that way rather than let them all die? Yes, but not by much.

  11. Hi Alicia, based on reading your comment- here is something you might find interesting! There is in fact a non-profitable conservation organization aimed at frogs, it is called “Save The Frogs!”, and it is based in America. They have a strong focus on educating people about awareness of how to protect frogs and educate school children/ people across multiple countries. They also protect wetlands from human intervention. While they aren’t as big as “Save The Rhino’s!” they have grown a lot since they opened in 2008 and now there is even a national Frog Day on 7 April.I don’t know what their stand is on amphibian trade, but its possible they’ve tried to address that issue. Check them out at http://www.savethefrogs.com, help spread awareness.

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