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Traits in Agriculture » Herbicide Tolerance

Title: Glyphosate Shown to Increase Honeybee Susceptibility to Infections
Publication date: October 02, 2018
Posting date: October 02, 2018

 THIRD WORLD NETWORK BIOSAFETY INFORMATION SERVICE


Dear Friends and Colleagues

Glyphosate Shown to Increase Honeybee Susceptibility to Infections

Increased mortality of honey bee colonies has been attributed to several factors but is not fully understood. The herbicide glyphosate (commonly sold as Roundup) is claimed to be innocuous to animals, including bees. However, a new study has found that exposing bees to glyphosate alters the bee gut microbiota and increases the insects’ susceptibility to deadly infections by pathogens. This is because some of the key beneficial bacteria in bees’ guts have the particular enzyme that is targeted by glyphosate.

Bees rely on a specialized gut microbiota that benefits growth and provides defense against pathogens. The study demonstrated that the relative and absolute abundances of dominant gut microbiota species decreased in bees exposed to glyphosate at concentrations documented in the environment. Young worker bees exposed to glyphosate exposure died more often when later exposed to a common bacterium. Thus, exposure of bees to glyphosate can perturb their beneficial gut microbiota, potentially affecting their health and effectiveness as pollinators.

The findings show that glyphosate, whose use has risen with the expansion of GM herbicide-resistant crops,may be contributing to the global decline in bees, along with the loss of habitat. Other research has shown that honeybee larvae grew more slowly and died more oftenwhen exposed to glyphosate. An earlier study showed the exposure of adult bees to the herbicide at levels found in fields “impairs the cognitive capacities needed for a successful return to the hive”.

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Item 1

GLYPHOSATE PERTURBS THE GUT MICROBIOTA OF HONEY BEES

by Erick V. S. MottaKasie Raymann, and Nancy A. Moran
The Proceedings of the National Academy of Sciences(PNAS)
24 Sept 2018
https://doi.org/10.1073/pnas.1803880115
http://www.pnas.org/content/early/2018/09/18/1803880115

Significance

Increased mortality of honey bee colonies has been attributed to several factors but is not fully understood. The herbicide glyphosate is expected to be innocuous to animals, including bees, because it targets an enzyme only found in plants and microorganisms. However, bees rely on a specialized gut microbiota that benefits growth and provides defense against pathogens. Most bee gut bacteria contain the enzyme targeted by glyphosate, but vary in whether they possess susceptible versions and, correspondingly, in tolerance to glyphosate. Exposing bees to glyphosate alters the bee gut community and increases susceptibility to infection by opportunistic pathogens. Understanding how glyphosate impacts bee gut symbionts and bee health will help elucidate a possible role of this chemical in colony decline.

Abstract

Glyphosate, the primary herbicide used globally for weed control, targets the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) enzyme in the shikimate pathway found in plants and some microorganisms. Thus, glyphosate may affect bacterial symbionts of animals living near agricultural sites, including pollinators such as bees. The honey bee gut microbiota is dominated by eight bacterial species that promote weight gain and reduce pathogen susceptibility. The gene encoding EPSPS is present in almost all sequenced genomes of bee gut bacteria, indicating that they are potentially susceptible to glyphosate. We demonstrated that the relative and absolute abundances of dominant gut microbiota species are decreased in bees exposed to glyphosate at concentrations documented in the environment. Glyphosate exposure of young workers increased mortality of bees subsequently exposed to the opportunistic pathogen Serratia marcescens. Members of the bee gut microbiota varied in susceptibility to glyphosate, largely corresponding to whether they possessed an EPSPS of class I (sensitive to glyphosate) or class II (insensitive to glyphosate). This basis for differences in sensitivity was confirmed using in vitro experiments in which the EPSPS gene from bee gut bacteria was cloned into Escherichia coli. All strains of the core bee gut species, Snodgrassella alvi, encode a sensitive class I EPSPS, and reduction in S. alvi levels was a consistent experimental result. However, some S. alvi strains appear to possess an alternative mechanism of glyphosate resistance. Thus, exposure of bees to glyphosate can perturb their beneficial gut microbiota, potentially affecting bee health and their effectiveness as pollinators.


tem 2

MONSANTO'S GLOBAL WEEDKILLER HARMS HONEYBEES, RESEARCH FINDS

Damian Carrington
The Guardian
24 Sept 2018
https://www.theguardian.com/environment/2018/sep/24/monsanto-weedkiller-harms-bees-research-finds

Glyphosate – the most used pesticide ever – damages the good bacteria in honeybee guts, making them more prone to deadly infections

The world’s most used weedkiller damages the beneficial bacteria in the guts of honeybees and makes them more prone to deadly infections, new research has found.

Previous studies have shown that pesticides such as neonicotinoidscause harm to bees, whose pollination is vital to about three-quarters of all food crops. Glyphosate, manufactured by Monsanto, targets an enzyme only found in plants and bacteria.

However, the new study shows that glyphosate damages the microbiota that honeybees need to grow and to fight off pathogens. The findings show glyphosate, the most used agricultural chemical ever, may be contributing to the global decline in bees, along with the loss of habitat.

“We demonstrated that the abundances of dominant gut microbiota species are decreased in bees exposed to glyphosate at concentrations documented in the environment,” said Erick Motta and colleagues from University of Texas at Austin in their new paper. They found that young worker bees exposed to glyphosate exposure died more often when later exposed to a common bacterium.

Other research, from China and published in July, showed that honeybee larvae grew more slowly and died more oftenwhen exposed to glyphosate. An earlier study, in 2015, showed the exposure of adult bees to the herbicide at levels found in fields “impairs the cognitive capacities needed for a successful return to the hive”.

“The biggest impact of glyphosate on bees is the destruction of the wildflowers on which they depend,” said Matt Sharlow, at conservation group Buglife. “Evidence to date suggests direct toxicity to bees is fairly low, however the new study clearly demonstrates that pesticide use can have significant unintended consequences.”

Prof Dave Goulson, at the University of Sussex, said: “It now seems that we have to add glyphosate to the list of problems that bees face. This study is also further evidence that the landscape-scale application of large quantities of pesticides has negative consequences that are often hard to predict.”

However, Oliver Jones, a chemist at RMIT University in Melbourne, Australia, said: “To my mind the doses of glyphosate used were rather high. The paper shows only that glyphosate can potentially interfere with the bacteria in the bee gut, not that it actually does so in the environment.”

A spokesman for Monsantosaid: “Claims that glyphosate has a negative impact on honey bees are simply not true. No large-scale study has found any link between glyphosate and the decline of the honeybee population. More than 40 years of robust, independent scientific evidence shows that it poses no unreasonable risk for humans, animal, and the environment generally.”

The new research, published in the Proceedings of the National Academy of Sciences, found that some of the key beneficial bacteria in bees’ guts have the enzyme that is targeted by glyphosate. It also found that the ability of newly emerged worker bees to develop a normal gut biome was hampered by glyphosate exposure.

Harm to gut bacteria by glyphosate exposure has also been shown in a pilot study in rats. “Gut bacteria play a vital role in maintaining good health, in organisms as diverse as bees and humans,” said Goulson. “The finding that these bacteria are sensitive to the most widely used pesticide in the world is thus concerning.”

People are known to widely consume glyphosate residuesin food - such as children’s breakfast cereal- but the health impact is controversial. In August a US court ordered Monsanto to pay $289m in damagesafter a jury ruled that the weedkiller caused a terminally ill man’s cancer. The company filed papers to dismiss the caseon 19 September.

The weedkiller, sold as Roundup, won a shortened five-year lease in the EU in 2017. In 2015, the World Health Organisation’s cancer agency, the IARC, declared glyphosate “probably carcinogenic to humans,” although several international agenciessubsequently came to opposite conclusions. Monsanto insists glyphosate is safe.


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