Distance measurements and phylogenetic analyses. Phylogenetic relationships were evaluated with use of Mega 4.1 (http:// www.megasoftware.net/mega41.html) [34] . Neighbor-joining trees were inferred using a matrix of pair-wise maximum-likelihood distances computed from a nucleotide alignment including the genomes obtained in this study and in GenBank, plus a matrix of PAM distances computed from the inferred amino acid alignment.