FIG. 2.

Unrooted phylogenetic trees of sesquiterpene synthase homologs identified in completed bacterial sequences available in the NCBI database. (A) Unrooted phylogenetic tree of single-domain sesquiterpene synthase homologs. (B) Unrooted phylogenetic tree of germacradienol/geosmin synthase-like homologs composed of two fused terpene synthase domains. Sequences were identified by BLAST using known bacterial sesquiterpene synthases. In the case in which sequences of several strains of a bacterial species were available, the sesquiterpene synthase sequence(s) of only one representative strain was selected for sequence analysis. Alignments of sequences used for tree building are shown in Fig. S1 in the supplemental material. Phylogenetic tree branches are labeled with accession numbers followed by species names for each sesquiterpene synthase sequence. Nostoc terpene synthase described in this study are indicated in brackets. Note that some species have several terpene synthase paralogs.