14 | NewScientist | 17 July 2010

GENES borrowed from Arctic bacteria could generate safer vaccines against diseases like tuberculosis. The genes enable researchers to make temperature-sensitive bacteria that prime the immune system before dying back.

So say Francis Nano and colleagues at the University of Victoria in British Columbia, Canada. They replaced genes in Francisella tularensis bacteria

with versions from different species of bacteria found in the Arctic. The Arctic genes evolved in freezing temperatures and stop functioning at the higher temperatures inside animals.

The team chose genes indispensable for survival, such as those that repair DNA, so that their engineered bacteria would die when the genes stopped working.

The team successfully

Single star count ups odds of aliens

SOLITARY suns like ours are not as rare as we once thought, boosting the likelihood that there are other planets on which life has evolved.

Surveys had suggested that most systems containing a star the same mass as our sun have two or more stars orbiting each other. But when Deepak Raghavan of Georgia State University in Atlanta and colleagues looked at 454 such stars, they found that 56 per cent were single like our sun and just 44 per cent had a stellar companion (arxiv.org/abs/1007.0414). Their study will be published in The Astrophysical Journal.

Single stars provide a stable planetary system where life is more likely to evolve. Planets can form in multiple star systems, but the gravity of the additional stars can hurl planets into their parent star, says John Chambers of the Carnegie Institution for Science, based in Washington DC.

The simple law of hurricanes decrees a stormy future

The intensity of hurricanes follows a simple mathematical law – a finding that could help predict how the storms will respond to climate change.

Álvaro Corral of the Centre for Mathematical Research in Barcelona, Spain, and colleagues looked at records of hurricanes from four ocean basins around the world between 1966 and 2007. They calculated how much energy each recorded hurricane released, based on its wind speeds and how long it lasted.

The researchers found that the proportion of rarer, strong hurricanes to commoner, weaker ones was always

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Vaccines that came in from the cold vaccinated mice against normally fatal doses of F. tularensis by first injecting their tails with the temperature-sensitive version (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1004119107).

The bacteria managed to survive within the lower temperatures of the skin, allowing it to prime the immune system, but was not present in internal organs, so posed no threat of disease. “TB is our big target now,” says Nano.

the same. Only the very weakest and the very strongest hurricanes did not fit the pattern, called a power law.

The team also looked at the effect of sea surface temperatures on hurricanes. The proportion of weak to strong hurricanes in each year was similar whether the sea was warm or cold that year, but more of the most powerful hurricanes were observed in warm years (Nature Physics, DOI: 10.1038/nphys1725).

Corral says that the finding hints that rising temperatures due to climate change will bring more of the most powerful hurricanes, but cautions it is difficult to say for sure. James elsner of Florida State University in Tallahassee is less sanguine, however. “Their results show that you get more powerful hurricanes if the sea surface temperatures are higher,” he says.

THE tyrant lizards were not above scavenging for a free lunch.

Tooth marks found on the fossilised humerus of a plant-eating dinosaur found in Mongolia show that a large tyrannosaur removed the meat from the bone, yet the rest of the skeleton showed no sign it had been attacked.

David Hone at the Institute of Vertebrate Palaeontology and Palaeoanthropology in Beijing, China, and Mahito Watabe of the Hayashibara Museum of Natural Sciences in Okayama, Japan, report that tooth marks on the 70-million-year-old bone match the pattern and shape of the teeth of Tarbosaurus, an Asian tyrannosaur nearly as big as T. rex (Acta Palaeontologica Polonica, DOI: 10.4202/app.2009.0133).

Tyrannosaurs not above scavenging

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