Nature 437, 376–380 (2005)10.1038/nature03959

The following were omitted from the original author listing: Alex de Winter, James Drake, Robin Forte, Steve Hutchinson, William L. Lee, Michael Reifler and David A. Willoughby. These names are included in the revised authorship shown here and either were or are at 454 Life Sciences Corporation, Branford, Connecticut 06405, USA.