Diesel exhaust pollution may disrupt honeybee foraging

A colony of honeybees swarm on the ledge of a window outside the Media Centre, in Bern June 17, 2013.

Credit: Reuters/Ruben Sprich

By Kate Kelland

LONDON | Thu Oct 3, 2013 9:07am EDT

LONDON (Reuters) - Exposure to pollution from diesel exhaust fumes can disrupt honeybees' ability to recognize the smells of flowers and could in future affect pollination and global food security, researchers said on Thursday.

In a study published in the Nature journal Scientific Reports, scientists from Britain's University of Southampton found that the fumes change the profile of the floral odors that attract bees to forage from one flower to the next.

"This could have serious detrimental effects on the number of honeybee colonies and pollination activity," said Tracey Newman, a neuroscientist who worked on the study.

Bees are important pollinators of flowering plants, including many fruit and vegetable crops.

A 2011 U.N. report estimated that bees and other pollinators such as butterflies, beetles or birds do work worth 153 billion euros ($203 bln) a year to the human economy.

Bee populations have been declining steadily in recent decades but there is scientific disagreement over what might be causing it. Much attention has been focused on whether a class of pesticides called neonicotinoids may be the culprit.

A report from the European Food Safety Authority (EFSA) in January said three widely-used neonicotinoids, made mainly by Switzerland's Syngenta and Germany's Bayer, posed an acute risk to honeybees.

EU leaders voted in April to ban three of the world's most widely-used pesticides in this class for two years because of fears they could be linked to a plunge in the bee populations.

But the British government, which recommended abstaining in a previous EU vote in March, argues the science is inconclusive and advises caution in extrapolating results from laboratory studies to real-life field conditions.

SENSITIVE SMELL

Guy Poppy, an ecology professor who worked with Newman, said to be able to forage effectively, honeybees need to be able to learn and recognize plants - a process their results showed could be disrupted by so-called NOx gases, particularly nitrogen dioxide, found in diesel exhaust and other pollution.

For their study, the scientists took eight chemicals found in the odor of oil rapeseed flowers and mixed them in one experiment with clean air and in another with air containing diesel exhaust.

They found that six of the eight chemicals reduced in volume when mixed with diesel fumes, and two disappeared completely within a minute - meaning the profile of the chemical mix had changed. The odor mixed with clean air was unaffected.

When the researchers used the same process with NOx gases - nitric oxide and nitrogen dioxide - found in diesel exhaust emissions, they saw the same results, suggesting NOx is key to how and why the odor's profile was altered.

When the changed chemical mix was then shown to honeybees - which are known to use their sensitive sense of smell to forage for flowers - they could not recognize it.

Giles Budge of Britain's Food and Environment Research Agency said Newton's study highlighted "a fresh issue to add to the many problems facing our insect pollinators".

But he said that since the study was based in the laboratory, more research is needed to see if the problem is occurring in the wider environment.

(Editing by Pravin Char)

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Gut Microbe Makes Diesel Biofuel

Reconfiguring the genetics of the food pathogen E. coli produces hydrocarbons indistinguishable from those burned in trucks

By David Biello

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E. coli can now replicate the hydrocarbon molecules that burn predominantly in big trucks and other powerful moving machines. Image: Flickr/Carlos de Paz

Welding bits and pieces from various microbes and the camphor tree into the genetic code of Escherichia coli has allowed scientists to convince the stomach bug to produce hydrocarbons, rather than sickness or more E. coli. The gut microbe can now replicate the molecules, more commonly known as diesel, that burn predominantly in big trucks and other powerful moving machines.

"We wanted to make biofuels that could be used directly with existing engines to completely replace fossil fuels," explains biologist John Love of the University of Exeter in England, who led the research into fuels. "Our next step will be to try to develop a bacterium that could be deployed industrially." Love’s work was published April 22 in Proceedings of the National Academy of Sciences.

That means harnessing E. coli's already high tolerance for harsh conditions, such as the high acidity and warmth of the human digestive tract. That hardiness also seems to be helping the bacterium survive its own production of such longer-chain hydrocarbons, which could have proved toxic to the microbes, in the way brewer's yeast cells are killed off by the alcohol they ferment. The engineered E. coli used genetic code from the insect pathogen Photorhabdus luminescens and from the cyanobacterium Nostoc punctiforme as well as soil microbe Bacillus subtilis to make the fuel molecules from fatty acids, along with a gene from the camphor tree—Cinamomum camphora—to cut the resulting hydrocarbon to the right length.

The E. coli are currently fed on sugar and yeast extract, which suggests that the resulting fuel would be expensive compared with the kind refined from oil found in the ground. "We are hopeful that we could change their diet to something less valuable to humanity," Love suggests. "For example, organic wastes from agriculture or even sewage."

Exactly how the E. coli microbes expel the diesel fuel molecules is unknown at this point. The researchers have found them floating in the growth medium, suggesting the microbes are somehow secreting the hydrocarbons from their cells once produced. "We don't know how they get there yet," Love admits. But that may solve a problem posed to other would-be biofuels produced in microbes; algal oils have proved difficult to extract cheaply and effectively from inside the algae themselves, among other challenges.

Besides a better grasp of the process itself, fine-tuning the genetic engineering may one day yield other useful hydrocarbons, such as jet fuel or even gasoline (a short-chained hydrocarbon). Similar work at the University of California, Berkeley, has tinkered with E. coli genetics to allow the bacteria to digest the inedible parts of plants known as cellulose and turn them into microbial diesel that can be used in place of fossil-fuel diesel or other useful hydrocarbons. And E. coli has been harnessed in the past to make specialty oils for cosmetics; the company Amyris makes the moisturizing oil known as squalane from E. coli fed sugarcane and grown in vats in Brazil. The synthetic biologists at Amyris have also coaxed yeast to produce the antimalarial drug artemisinin, a technology that is currently being commercialized with drugmaker Sanofi.

Regardless, industrial-scale fuel production from microbes remains a much tougher proposition than making specialty oils or medicines, given the low cost and high volumes required to compete with the fuels made from fossil sources. "Fuel is actually a lot cheaper than artemisinin, so it has to be made in significantly larger quantities," Love notes. "That in itself is a challenge."

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