Genome Analysis of Rhizobium Species using Codon Usage Bias Tools

Bacteria from genus Rhizobium have ability to fix atmospheric nitrogen in symbiosis with leguminous plants resulting in formation of root nodules. They act as an alternate source of nitrogenous fertilizers. The study of codon usage patterns of Rhizobium species is gaining increasing attention over the times. In the present study three strains of Rhizobium namely Sinorhizobium meliloti 1021, Bradyrhizobium japonicum USDA110 and Rhizobium tropici CIAT899 whose complete genome sequence are available were retrieved from NCBI for the analysis of codon usage. The overall codon usage analysis showed that codons ending with G and C are preferred more in the rhizobium genome than codon ending with A and T. ENc plot revealed that compositional constraints along with translational selection are the major cause of codon usage bias. Correspondence analysis (COA) showed that the variation in codon usage is accounted mainly by the first two axes. From the Pearson correlation analysis significant correlation was identified among the first axis of COA and Codon adaptation index (CAI) and other factors of codon usage bias. 17 optimal codons were identified that were shared among these three strains.