Nature Biotechnology 24, 1385–1391 (2006); published online 22 October 2006; corrected after print 26 March 2007

In the version of this article initially published, the gene name nosRZDYFLX on p. 1388, left column, line 5, is incorrect; the correct name is nosZRDFYL. The error has been corrected in the PDF version of the article.