The inbuilt database consists of prokaryotic genomes downloaded from the NCBI FTP site (ftp://ftp.ncbi.nlm. nih.gov/genomes/Bacteria/) and fungal genomes collected manually. Only the compressed faa, rpt and gbk files are downloaded. The ffn files are locally extracted from the gbk files by the program extractfeat in the EMBOSS package (20) . Judging by the DEFINITION line in the gbk files, files that represent plasmids, mitochondria, phages or extrachromosomal elements are not fetched. Only chromosomal sequences are used. The NCBI Taxonomy ID was extracted from the rpt file of each organism. As of 1 April 2009, there were 799 bacteria and 56 archaea genomes. More than 80 fungal genomes have been collected manually from various sequencing projects. These fungal genomes together with their origin are listed in the online user's manual. The NCBI Taxonomy ID of fungi is assigned manually. (Currently some manually collected genomes including some fungi do not contain the ffn files, therefore could not be used to perform the DNA type calculation.) We have also included a few eukaryote genomes frequently used as outgroup in previous publications to bring the total number of built-in genomes to 941. This number will grow with monthly updates.