Phylogenetic tree of T. thermophila P450 genes with intron location analysis. Left: The NJ tree with bootstrap values. Right: Predicted P450 gene sequences were drawn as dotted lines, gene sequences with available ESTs were drawn as straight lines. A phase zero splice site lies between two codons, while a phase I splice site lies one base inside a codon in the 3' direction, and a phase II intron is two bases inside a codon in the 3' direction. Intron organization: Green, phase zero; Red, phase I; Blue, phase II. Consensus Introns that share the same aligned position are enclosed in a black square. The three largest families are enclosed in the colored squares.