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Bacteria do not use arsenic after all
In December 2010, NASA and USGS scientist Dr Felisa Wolfe-Simon and her team published a controversial claim in Science that life can use arsenic for growth. But this week, two studies in the same journal refute the original evidence.

Wolfe-Simon's team examined a bacterium, GFAJ-1, from the arsenic-rich Mono Lake in California. They claimed that the organism could use arsenic instead of phosphorus for growth, and that it was used within the bacterium's DNA. These claims have been challenged by the latest publications, which were released by separate groups who took complementary approaches.

The ETH Zurich group, headed by Dr Tobias Erb, found that GFAJ-1 was likely to have grown on the small quantity of phosphate that remained as an impurity in Wolfe-Simon's experiment.

The Princeton University and University of British Columbia collaboration also found that in low-phosphate environments, GFAJ-1 does not use arsenate for growth. They analysed the bacterium's DNA and saw only trace amounts of free arsenate – none was bound into the structure.

Solar Army
High school chemistry students have a new after-school activity: Saving the world. They are trying to combat global warming by using an inexpensive Solar Hydrogen Activity Research Kit – or SHARK – aiming to find metal oxides that can use sunlight to split water. The hydrogen produced could then be used instead of fossil fuels.

The so-called Solar Army of young people is led by Professor Harry Gray at Caltech.

Magnetic sensing
From fifty years' worth of experiments conducted with migratory birds, marine turtles and cattle – amongst many others – we know that many animals have an internal magnetic compass. But although we have substantial evidence of such behaviour, scientists are still trying to work out exactly how organisms are able to use Earth's magnetic field.

Fifteen years ago, researchers made a leap in progress when examining the rainbow trout’s response to magnetism. They identified parts of the fish’s nose that could be magnetoreceptors – areas that detect subtle changes in the magnetic field that surrounds us. The problem that then arose was surprisingly difficult to solve: how could individual magnetism-detecting cells be found for further study?

Now, a team from LMU University in Munich have built upon this work by developing a surprisingly simple method. In a paper published in the journal PNAS this week, Professor Michael Winklhofer and his team explain how they use a rotating magnetic field to spot the one in 10,000 cells that spin, indicating their magnetic properties.