Comparison of codon usage in S. barkhanus and S. salmonicida. (A) The effective number of codons (Nc') plotted against the G+C content in four-fold degenerate positions in the gene (GC3s) for 682 unique S. barkhanus genes. (B) Correspondence analysis of the relative synonymous codon usage (RSCU) of the 682 unique S. barkhanus genes. (C) GC3s of aligned regions of 233 pairs of putative S. barkhanus and S. salmonicida orthologs. (D) The difference of GC3s of aligned regions of putative orthologs plotted against the non-synonymous divergence values (dN). The color coding indicates the number of times the gene was sampled within the S. barkhanus EST data.