Analyses of nucleotide, synonymous codon and amino acid usages at gene levels of Brucella melitensis strain QY1.

Brucella melitensis is the causative pathogen of the zoonotic disease brucellosis in China. This work focused on analyses of genetic features represented by nucleotide, synonymous codon and amino acid usages at gene levels of B. melitensis strain QY1 isolated from China. Although nucleotide usage biases at different codon positions all work on synonymous codon usage bias, nucleotide usage biases at the 1st and 3rd positions play more important roles in codon usages. Mutation pressure caused by nucleotide composition constraint influences the formation of over-representative synonymous codons, but neighboring nucleotides surrounding a codon strongly influence synonymous codon usage bias for B. melitensis strain QY1. There is significant correlation between amino acid usage bias and hydropathicity of proteins for B. melitensis strain QY1. Compared with different Brucella species about synonymous codon usage patterns, synonymous codon usages are not obviously influenced by hosts. Due to nucleotide usage bias at the 1st codon position influencing synonymous codon and amino acid usages, good interactions among nucleotide, synonymous codon and amino acid usages exist in the evolutionary process of B. melitensis.