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Published online: 3 May 2007; | doi:10.1038/news070430-8 / http://www.nature.com/news/2007/070430/full/070430-8.html

Probiotics could save frogs

Bacterial baths help amphibians fight off fungus. / Helen Pearson

The Mountain yellow-legged frog of California is plagued by fungal infections. NHPA

Planting bacteria on frogs' skin might help to save amphibians from their global decline, hints new research. The work shows that frog probiotics can help to fight off a lethal fungus.

Many populations of amphibians are plummeting, and some have already gone extinct. One of the major causes is a fungus called Batrachochytrium dendrobatidis, which lives on the skin of some frogs and salamanders.

As in humans, amphibians host a community of bacteria on their skin. So Reid Harris at James Madison University in Harrisonburg, Virginia, wondered whether the community carried by amphibians susceptible to B. dendrobatidis had lost its ability to fight off the fungus.

To test this idea, Harris and his colleagues isolated different bacteria species from the skin of a common salamander. They put the each of these species on top of some B. dendrobatidis growing in a Petri dish - and found that several of them killed off a patch of the fungus.

Now they have shown that at least one of these bacterial species - Pedobacter cryoconitis - can help amphibians to survive. The team allowed red-backed salamanders to swim in a bath of this bacteria for two hours, and then infected them with the lethal fungus.

When tested 18 days later, the salamanders given the bacterial bath were nearly 30% more likely to have rid themselves of the fungal infection than were the untreated animals. Harris speculates that the bacterium is probably making a natural antibiotic. He reported his results at a meeting on microbes and conservation at the American Museum of Natural History in New York on 26 April.

Another bacterium, called Pseudomonas reactans, actually made the salamanders more susceptible to the fungus, perhaps because it displaced regular, infection-fighting bacteria from the skin.

Stressed-out skin

Harris suggests that environmental stresses such as climate change or pollution might change an amphibian's community of skin bacteria. The stressed animals might make less skin mucus, on which the bacteria feed, or they may make more stress hormones, which would encourage different bacterial species.

Exposing threatened amphibians to the fungus-fighting bacteria, perhaps by adding it to ponds or sites that they frequent, might help to reverse some of the population decline, Harris suggests. With few other options available, this strategy is worth pursuing, he says: "It's the only thing that's offered a glimmer of hope".

"I think it's a very promising area that needs to be pursued," says Louise Rollins-Smith, who studies amphibian immunology at Vanderbilt University in Nashville, Tennessee. "It's such an important conservation problem. Any information on a mechanism that could protect them is valuable."

Because it is unclear how long the effect of the bacteria will last, the microbes might have to be introduced again and again.

The idea is akin to the probiotic food and drinks that some people swallow to try and change the community of microbes living in their guts. Some researchers are also toying with the idea of developing probiotics for human skin. Probiotics have also been used in aquaculture - in fish food or simply in the water - to try and increase yields.

Harris now plans to collaborate with colleagues in California to test whether the probiotic protects the Mountain yellow-legged frog (Rana muscosa), an endangered species that usually succumbs to the fungus.

References : Harris R. N., James T. Y., Lauer A., Simon M. A. & Patel A. . EcoHealth, 3 . 53 - 56 (2006).

Published online: 4 May 2007; | doi:10.1038/news070430-14 / http://www.nature.com/news/2007/070430/full/070430-14.html

GM patent rejected after 13 years

Patent for technology to fire genes into soy seeds thrown out.

Ned Stafford

The European Patent Office (EPO) has revoked a patent owned by global agricultural giant Monsanto for the genetic modification (GM) of soybeans, saying the technique it approved 13 years ago lacked "novelty".

The technique, which describes a way of creating any kind of GM soybean without reference to the specific genes being introduced, has helped make Monsanto the dominant force in GM soybeans - the company owns nearly 90% of the global market. Opponents complained that the patent gave Monsanto de facto control over all GM soybeans, and have been fighting against it since it was granted in 1994.

At a hearing on 3 May, the EPO revoked the patent. The board's decision is final, says Rainer Osterwalder, spokesman for the EPO, with no further appeals available.

The decision will no doubt have an impact on other GM technology patents, Osterwalder told Nature. "Case law is important," he says.

But the patent was due to expire in 2008 anyway. A spokesperson for Monsanto says: "We do not expect this decision to have an impact on Monsanto's business." The EPO will not issue a detailed written explanation of the legal basis of its decision for three to six months, Osterwalder says.

Published online: 4 May 2007; | doi:10.1038/news070430-13 / http://www.nature.com/news/2007/070430/full/070430-13.html

Maggots eat up resistant bacteria

Creepy crawlies are the latest weapon in the anti-MRSA arsenal.

Katharine Sanderson

It looks bad, but it works: maggots can clean out some foot wounds better than drugs.

The drug-resistant bug MRSA has a new adversary - the maggot. Researchers in Manchester, UK, have just won a grant to compare maggots with other more hi-tech treatments for people with diabetes who suffer from infected feet.

A quarter of all people with diabetes are at risk of foot ulcers, because of the reduced blood circulation caused by the damaging effects of high blood glucose. These lesions often become infected. Antibiotic-resistant bacateria such as methicillin-resistant Staphylococcus aureus (MRSA) are becoming increasingly common - and consequently increasingly hard to treat. "MRSA is not just in hospitals, it's everywhere," says team leader Andrew Boulton at Manchester University.

Antibiotics prove useless against these bugs. So Boulton decided to turn his attention to maggots. These creatures have been called into action to chew up infected tissues ever since the American Civil War, and have been used in diabetes clinics for a decade. Boulton wanted to see how they fared against MRSA.

A small initial trial, published this February, showed considerable success. 'Larval therapy' (the polite term for maggot treatment) was excellent for shifting MRSA infected tissue: in 12 out of 13 patients, their wounds healed after between three and five applications of maggots, each lasting four to five days. "It's primitive but effective," says Boulton.

The charity Diabetes UK has now given Boulton £98,000 (US$195,000) to test maggots versus two other treatments: silver-containing dressings and a biogun - which zaps infection by ionizing molecular oxygen and creating bug-beating superoxide radicals. The trial will involve a total of 65 patients and will begin within a few months. Boulton expects the maggots to fare the best : "We hope that this trial will confirm our findings" he says.

The trial has been temporarily held up because the UK's Medicines and Healthcare products Regulatory Agency claims that the ancient maggot-healing technique is a new therapy that requires a special licence. But Boulton expects to overcome this hurdle within a few weeks.

Boulton is also collaborating with microbiologists to find out how the treatment works. The maggots might secrete an antibacterial goo, or they might be just devouring the infected flesh. Boulton has noticed that the MRSA infection is highly concentrated around the maggots - rather like iron filings around a magnet, he says. But at the moment how and why this happens is a mystery.

References : Bowling F. L., Salgami E. V., Boulton A. J. M., et al. Diabetes Care, 30 . 370 - 371 (2007).

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En vidéo : des asticots pour nettoyer nos plaies ! http://www.futura-sciences.com/fr/sinformer/actualites/news/t/medecine/d/en-video-des-asticots-pour-nettoyer-nos-plaies_11794/

Published online: 4 May 2007; | doi:10.1038/news070430-11 / http://www.nature.com/news/2007/070430/full/070430-11.html

Tackling greenhouse gases looks to be affordable

International report sets out costs of bringing down global emissions.

Michael Hopkin

Bringing greenhouse gas emissions under control looks to be both achievable and affordable, on the basis of the most recent report of the Intergovernmental Panel on Climate Change (IPCC).

Today marks the end of an often fraught week of talks by the IPCC's Working Group III, which evaluates strategies to counter the rising levels of greenhouse emissions.

Their summary report, released in Bangkok, Thailand, says that stabilizing atmospheric greenhouse gases at a level likely to avoid the worst effects of global warming would cost no more than 3% of global economic productivity by 2030 - an average of 0.12% per year.

This is cheaper than many observers had expected it to be, and most see it as affordable; environmental groups represented on the panel, such as Greenpeace, have called it a small price to pay.

But US officials say that this would lead to a global recession, and argue that greenhouse levels should be stabilized at a higher level. "This report underscores the importance of a strong curve of emissions reductions," says James Connaughton, chair of the White House Council on Environmental Quality. "But no world leader will pursue a strategy that would lead to economic recession."