Arsenic-munching bacteria found

Microbial biofilms form in rocky pools, fed by hot springs containing arsenic

In the warm, bubbling pools of Mono Lake in California, scientists have isolated a bacterium that fuels itself on arsenic.

Combining light and arsenic, these bacteria make their food and multiply using a chemical that is toxic to most other life forms.

The researchers think using arsenic as an energy source was a process used by ancient bacteria.

Their findings are reported in the journal Science.

Ronald Oremland of the US Geological Survey explained that these bacteria are photosynthetic, using sunlight – like plants – to turn carbon dioxide into food.

What is different about them is that instead of using water in this process, they use arsenic.

The US-based researchers isolated the bacterium from the lake, which lies at the foot of the Sierra Nevada.

Colour film

“These lakes are fed by hydrothermal waters that leach out arsenic-containing minerals from the surrounding rocks,” Dr Oremland told.

The researchers noticed that the bacteria had colonised small, hot pools, forming colorful “biofilms”.

Bacteria living in Mono Lake, California can survive the high levels of arsenic

“We suspected that these bacteria were using arsenic to make a living, so we scraped the biofilms off the rock and studied them under laboratory conditions.”

By first withholding light, then arsenic, the team showed that the bacteria required both to grow.

This the first time an organism has been found that can use arsenic to photosynthesise under anaerobic conditions, Dr Oremland believes.

He suspects that this is an ancient ability in bacteria.

“We think that bacteria were photosynthesising before oxygen was present in the atmosphere,” he said.

Primordial niche

Understanding how arsenic is metabolized by bacteria could help scientists comprehend its damaging affects inside human cells.

Worldwide, 144 million people are exposed to toxic levels of arsenic in their drinking water.

It enters the body’s cells by diffusion; and once inside, it disrupts how they function by binding to their machinery, inactivating it, and disrupting the way energy is transported.

Long-term exposure can lead to skin disease and kidney and bladder cancer, and it is thought to stunt the intellectual development of children.

The most arsenic-contaminated regions are in India, Pakistan, and China, where soluble arsenic in ground waters is above the World Health Organization’s (WHO) suggested maximum safe level of 10 parts per billion.

Beijing ready for Olympic opening

Officials are concerned that hazy conditions may affect the ceremony

The Chinese capital, Beijing, is preparing to open the 2008 Olympic Games with a lavish ceremony, amid hazy skies and ongoing pollution concerns.

The event will involve about 10,000 performers, and will be watched on TV by an estimated one billion people.

The lead-up to the Games has been dogged by issues such as China’s rights record, internet access, and pollution.

US President George W Bush was among several world leaders to express concern over a crackdown on dissidents.

Mr Bush told an audience at the US embassy in Beijing on Friday: “We continue to be candid about our belief that all people should have the freedom to say what they think and worship as they choose.”

Meanwhile, 40 Olympic athletes wrote to Chinese President Hu Jintao expressing their concerns over Beijing’s handling of anti-Chinese unrest in Tibet.

And Tibetans have held angry protests in Nepal, with hundreds reported to have been arrested in the capital, Kathmandu.

China frequently dismisses criticism over its domestic policies – particularly in Tibet – as interference in its internal affairs.

Muted city

The 2008 Olympics have been described as the most politicised Games since the boycott era of the early 1980s.

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But after a succession of controversial issues in the build-up to the Games, the focus is now shifting to the opening ceremony.

It has taken seven years of planning, and costs are estimated to have hit a record-breaking $40bn (£20bn).

Film director Zhang Yimou has been charged with portraying 5,000 years of Chinese history in one show.

It will be staged at China’s new national stadium – known as the Bird’s Nest because of its steel lattice construction – and some 10,000 performers will take part.

Jacques Rogge, the head of the International Olympic Committee, who has repeatedly defended the decision to let China host the Olympics, said he hoped the Games would help the world to understand China, and China to understand the world.

But human-rights groups have continued to condemn curbs on journalists covering the Games.

In a statement issued on Friday, the New York-based group Human Rights Watch said: “As the 2008 Olympic Games open in Beijing, foreign journalists in China face a host of severe restrictions, ranging from harassment to a censored internet.”

With the authorities determined to clamp down on any possible security concern, some 100,000 extra troops and police have been deployed in the capital over recent weeks.

The BBC’s Michael Bristow, in Beijing, described the mood in the city as muted.

He said streets had been blocked off, there were few cars on the roads and Olympic volunteers seemed to outnumber ordinary people.

China’s ‘extraordinary’ effort

On the morning of the opening ceremony, a BBC reading suggested Beijing’s air quality remained below World Health Organization (WHO) standards.

Visibility was also very poor on Friday, with one official warning that the cloud could interfere with the ceremony.

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“There are clouds covering Beijing and we are really concerned that will have an influence on tonight’s ceremony,” said Guo Hu, director of the Beijing Meteorological Observatory.

But Mr Guo is predicting that heavy rain over the weekend will clear the skies, and he warned that hazy conditions should not be confused with high levels of pollution.

“If the visibility is not good it does not mean the air quality is not good,” he said.

On Thursday, Mr Rogge said if the pollution was bad, events which lasted more than an hour could be shifted or postponed.

But he also praised China’s “extraordinary” efforts to cut pollution ahead of the Games, saying there was no danger to athletes’ health.