Fig. 1

Hierarchical clustering of composite genes families according to their component origins (as assigned by BLAST). The heatmap represents the ratio of genes in a given family (columns) which have at least one component of a given origin (haloarchaeal, archaeal, bacterial or prokaryotic, rows). A white tick corresponds to the absence of components from a given origin in every gene in a given composite gene family. Colored ticks correspond to the presence of at least one component of a given origin at a given percentage (red for 100% of the genes in a composite gene family). The heatmap is hierarchically clustered by gene families. The colored top bar indicates the functional annotation of the composite gene families according to COG categories (red: metabolism, blue: information storage and processing, green: cellular processes and signaling, white: poorly characterized). The Euclidean distance and the complete linkage method were used for the hierarchical clustering