Phylogeny of Bacillus Subtilis Strains Cannot Be Resolved by 16S rRNA Due to Very Close Evolutionary Distance in the Gene

Abstract

Phylogenetic tree is the main method for understanding the evolutionary distance between different strains of the same species at the resolution of a specific gene. One commonly used gene for comparing phylogeny is 16S rRNA gene. This work explores the feasibility of gleaning useful understanding about the phylogeny of Bacillus subtilis strains using multiple sequence alignment of 16S rRNA gene followed by phylogenetic tree reconstruction. The resulting phylogenetic tree reveals very close evolutionary distance between 16S rRNA gene variants from different strains of B. subtilis of the order of 0.01 to 0.03 evolutionary distance units. This suggests that the phylogeny of B. subtilis strains could not be resolved using 16S rRNA gene phylogenetics and highlights the critical role that the B. subtilis 16S rRNA gene plays in the bacterium’s physiology and metabolism. Specifically, B. subtilis 16S rRNA gene must have been evolutionary tuned in sequence to its present form that allows it to bind to the ensemble of ribosomal proteins in the small and large ribosome subunits to afford a macromolecular protein translation complex that has the correct translation rate and codon decoding efficiency and accuracy to allow observed fast growth rate, and adaptation capability to environmental and nutritional conditions changes of the bacterium.

Keywords: Bacillus subtilis, phylogenetic tree, 16S rRNA gene, evolutionary distance, ribosome