Multiple Evolutionary Selections Involved in Synonymous Codon Usages in the Streptococcus agalactiae Genome

Area of Science:

• Microbiology
• Molecular Evolution
• Genomics

Background:

• Streptococcus agalactiae is a significant pathogen affecting both humans and animals.
• Understanding its genetic features and evolutionary dynamics is crucial for controlling infections.

Purpose of the Study:

• To investigate the factors influencing synonymous codon usage patterns in Streptococcus agalactiae.
• To determine the roles of mutational pressure, translational selection, and host interactions in shaping codon usage bias.

Main Methods:

• Analysis of synonymous codon usage patterns across the S. agalactiae genome.
• Utilized statistical methods including Principal Component Analysis (PCA).
• Evaluated compositional constraints, translational selection (GC3%, ENC, tAI, CAI, Fop), and gene length.

Main Results:

• Adenine (A)/Thymine (T) compositional constraints and translational selection significantly influence codon usage.
• Mutational pressure is the primary driver of codon usage in S. agalactiae ORFs.
• Codon usage patterns are independent of susceptible hosts (human and tilapia).

Conclusions:

• Mutational pressure and translational selection are key evolutionary forces in S. agalactiae codon usage.
• Gene length and strand-specific mutational bias do not significantly impact codon usage patterns.
• The findings provide insights into the molecular evolution and host-pathogen relationships of S. agalactiae.