Nav: Home

Land use may weaken amphibian's capacity to fight infection and disease

December 16, 2015

CLEVELAND--Man-made changes to the environment may be damaging the immune systems of a species of frog whose populations have drastically declined since the 1970s, according to a new study by researchers at Case Western Reserve University and the Holden Arboretum.

"These Blanchard's cricket frogs have nearly gone extinct in their northern range, so we're almost forensically trying to understand what happened," said Mike Benard, a biology professor at Case Western Reserve. "This study suggests that changes we are making to the environment have the potential to make animals more susceptible to diseases and therefore may lead to population declines."

Scientists found that habitat characteristics explained the differences in immune defense traits of frogs between populations. They found that the skin microbiomes ?symbiotic bacterial and fungal communities on the skin ?of frogs from disturbed sites, like residential and agricultural lands, were different from the skin microbiomes of frogs from more natural habitats. They also found natural peptide secretions--proteins frogs secrete from their skin that protect against pathogens--differed between frogs from different environments.

Both changes potentially alter the amphibian's immune defense capabilities.

These findings and more are published in the journal Biological Conservation.

Research is increasingly showing that microbiomes in the gut and on the skin and antimicrobial peptides excreted by humans and other animals play important roles in fighting infection and disease.

"We're seeing a lot of disease-related declines among amphibians, not to mention other groups of animals, such as bats plagued with white-nose syndrome and bees suffering from colony collapse disorder," said Katherine Krynak, a postdoctoral scholar in Case Western Reserve's Department of Biology and leader of the study. "This research shows that land use--farming or treating lawns with herbicides, pesticides and fertilizers--can influence traits that protect animals from disease."

Testing Blanchard cricket frogs

Blanchard's cricket frogs are about an inch long. They had once been widely spread across Wisconsin, Michigan and northern Ohio, but now only pockets remain in this northern region.

Frogs used in the study were from ponds in various habitats: natural ponds surrounded by forest or prairie, or more disturbed ponds surrounded by houses, on farmed land or near athletic fields, parking lots and golf courses. In addition to considering the physical differences, the researchers tested water chemistry and quality in each pond.

With permission from the states of Ohio and Michigan, Krynak, Benard and David Burke, a scientist and research chair at Holden Arboretum in Kirtland, Ohio, examined samples Krynak had collected from the frogs. Krynak used Q-tip like swabs to obtain samples of the skin microbiome, and then placed the frogs in a solution that gently induced the animals to secrete the antimicrobial peptides.

Krynak and Burke then used molecular methods to examine the community of microbes on the frogs' skin. Burke, who studies symbiotic interactions between plants and microbial communities, is also an adjunct assistant professor of biology at Case Western Reserve. Krynak and Burke also examined the amount of peptides the frogs produced and how effective the peptides were against an amphibian pathogen they cultured in the lab.

What they found

The researchers found microbiome differences between frogs that live in natural areas, such as a pond owned by the Nature Conservancy, and those in ponds surrounded by highly "managed" land, such as farmland or residential properties.

"What we're seeing is the bacteria on the skin can vary markedly, depending on what people are doing to the environment that the frogs are living in," Burke said.

A pond's latitude, conductivity--a proxy for chemical runoff--and size also appear to affect the microbiome.

The amount of natural peptide secretions produced from the frogs' skin also varied across sites and was influenced by both the size of the pond and the conductivity of the water.

At what cost?

Some of the skin secretions have been shown to fight off fungal infections, Krynak said. But in petri dishes in the lab, the growth rate of chytrid fungus, which has been linked to devastating population declines in amphibians worldwide, climbed with increasing Blanchard's cricket frog natural peptide secretions.

The researchers will further investigate why higher concentrations of peptides appear to allow the killer fungus to grow faster in this species.

"This pattern suggests that in areas where land use increases the amount of the peptides these frogs produce, this particular pathogen could have devastating effects" Krynak said.

The team will also look more directly at how the environment interacts with a population's genes, changing the expression of traits. "Not only may the environment be altering traits now, but it may be dampening the ability of a population to adapt in the future," Krynak said.

They are also experimentally isolating factors such as how a commonly used and commercially available glyphosate-based herbicide may alter these immune defense traits.

Environmental alteration of defense traits may explain why different amphibian populations show different levels of resistance to infection and disease.

Krynak said there's a strong chance that the environment is affecting these traits in other amphibians and wildlife in general.

"By improving our understanding of the factors influencing immune defense traits capabilities, we are given the opportunity to make changes to our land management practices to better protect wildlife health" she said "and in all likelihood, our own health as a consequence".
-end-


Case Western Reserve University

Related Peptides Articles:

Pigments by design
Researchers have discovered how to tune the optical and electrical properties of a synthetic polymer similar to melanin, a natural pigment that's the primary factor affecting skin color.
Frog slime kills flu virus
Frogs' skins were known to secrete peptides that defend them against bacteria.
Killing flu viruses with help from a frog
Frog mucus is loaded with molecules that kill bacteria and viruses, and researchers are beginning to investigate it as a potential source for new anti-microbial drugs.
A promising strategy to increase activity in antimicrobial peptides
In an article published recently in Plos One, researchers from INRS-Institut Armand-Frappier Research Centre reported a strategy that could lead to the discovery of new cationic antimicrobial peptides (CAMPs) with greatly enhanced antimicrobial properties.
Sequencing poisonous mushrooms to potentially create medicine
A team of Michigan State University scientists has genetically sequenced two species of poisonous mushrooms, discovering that they can theoretically produce billions of compounds through one molecular assembly line.
Peptides as tags in fluorescence microscopy
Advance in biomedical imaging: The Biocenter of the University of W├╝rzburg in close collaboration with the University of Copenhagen has developed an alternative approach to fluorescent tagging of proteins.
Team finds new way to attach lipids to proteins, streamlining drug development
Protein-based drugs are used in the treatment of every kind of malady, from cancer to heart disease to rheumatoid arthritis.
Machine-learning discovery and design of membrane-active peptides for biomedicine
There are approximately 1,100 known antimicrobial peptides (AMP) with diverse sequences that can permeate microbial membranes.
Toxic peptides disrupt membrane-less organelles in neurodegenerative disease
St. Jude Children's Research Hospital scientists reveal how toxic peptides that arise due to amyotrophic lateral sclerosis and frontotemporal dementia target the integrity of membrane-less organelles and trigger disease.
Peptides vs. superbugs
Several peptides have an antibacterial effect -- but they are broken down in the human body too quickly to exert this effect.

Related Peptides Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Moving Forward
When the life you've built slips out of your grasp, you're often told it's best to move on. But is that true? Instead of forgetting the past, TED speakers describe how we can move forward with it. Guests include writers Nora McInerny and Suleika Jaouad, and human rights advocate Lindy Lou Isonhood.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...