Published: Monday 31 October 2005

infinite genomes: Scientists at the Institute for Genomic Research in the US claim researchers might never fully describe some bacteria and viruses because their genomes are infinite. Each strain of a species may yield significant new genes, conclude Herv Tettelin and colleagues after comparing the genomic sequence of eight isolates of bacterium Streptococcus agalactiae, which mainly infects newborns.

They found a surprisingly continual stream of diversity of genes. Each strain contained an average of 1,806 genes constituting the core genome plus as many as 439 genes absent in one or more strains.

safe disposal: Placing shredded tyres on top of, rather than in, landfills can save money and benefit the environment, say researchers from the University of Illinois in the US.

Timothy Stark and Krishna Reddy evaluated the use of shredded tyres as a drainage material in waste-containment systems. They found tyres cut into roughly 10 centimentres by 15 cm pieces offer a cost-effective way of providing drainage for modern landfills, besides disposing of mountains of scrap tyres. A layer of tyre pieces prevents water from percolating through the waste and polluting the groundwater, Reddy said.

super surfers: Mathematicians at the Massachusetts Institute of Technology in the US have discovered how certain water insects can climb what to them are steep, slippery slopes or menisci in the water's surface without moving their limbs. Menisci arise when the water surface meets land or floating bodies and are like "frictionless mountains" for the tiny insects.

David Hu and John Bush took high-speed video of the insects, then digitised and analysed the images. They found the creatures adopt special postures that create forces pulling them up the slope at speeds of almost 30 body lengths per second (for comparison, an Olympian sprinter moves at about five body lengths per second).

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