Figure 1. Similarity of secondary metabolite profiles of Thalassospira strains at different taxonomic levels.

A small test database was constructed using 8 Thalassospira strains (4 of T. xiamenensis and 4 of T. profundimaris) and 1 Pseudovibrio denitrificans strain (as negative control). Four biological replicates of each Thalassospira strains were cultured, and its secondary metabolite profiles are searched against the test database. The similarity scores between each biological replicate and all possible answers were plotted as data points on a horizontal line with the following color code: biological replicates of the same strain (red), different Thalassospira strains in the same species (blue), different Thalassospira species in the same genus (green), and the P. denitrificans strain (black). The secondary metabolite profiles of the same strain show high biological reproducibility, and the secondary metabolite profile similarity approximately, but not always, correlates with taxonomical similarity. The profiles of strains differing at the genus level are sometimes more similar than those differing at the species level.