Comparative investigation of the various determinants that influence the codon and amino acid usage patterns in the genus Bifidobacterium.

Various strains of the genus Bifidobacterium are crucial members of the human, animal and insect gut, associated with beneficial probiotic activities. An extensive analysis on codon and amino acid usage of the GC rich genus Bifidobacterium has been executed in the present study. Multivariate statistical analysis revealed a coupled effect of GC compositional constraint and natural selection for translational efficiency to be operative in producing the observed codon usage variations. Gene expression level was inferred to be the most crucial factor governing the codon usage patterns. Amino acid usage was found to be influenced significantly by hydrophobic and aromatic character of the encoded proteins. Gene expressivity and protein energetic cost also had considerable impact on the differential mode of amino acid usage. The genus was found to strictly obey the cost-minimization hypothesis as was reflected from the amino acid usage patterns of the potential highly expressed gene products. Evolutionary analysis revealed that the highly expressed genes were candidates to extreme evolutionary selection pressure and indicated a high degree of conservation at the proteomic level. Interestingly, the complimentary strands of replication appeared to evolve under similar evolutionary constraints which might be addressed as a consequence of absence of replicational selection and lack of strand-specific asymmetry among the members of the genus. Thus, the present endeavor confers considerable know-how pertaining to the codon and amino acid usage intricacies in Bifidobacterium and might prove handy for further scientific investigations associated with the concerned domain.