A comprehensive phylogenetic study of the core genome of thirteen Bacillus and related species using known and novel techniques

A comprehensive study into the phylogeny of the Bacillus core genome was accomplished using two primary studies. The first study involved two previously studied methods, MUMmer and BSR, and one novel approach, RINC, to compare core genome phylogeny. BSR analysis revealed genomic rearrangements among the genomes of interest. MUMmer was used to confirm these genomic rearrangements and provide evidence that 76.2% of the inverted regions were statistically significant. Circular chromosome comparisons connecting homologous core genes revealed an ancestral inversion pivoted on the terminus in several species. The inversions were resolved, allowing for the identification of the location of the core genome before the inversion event. These analyses led to development of a novel approach to core genome phylogeny, RINC. Based on the tree produced, as well as agreement of groups of nodes with previous studies, the RINC approach was successful at comparing the core genome of Bacillus. RINC offers a simplistic yet powerful tool for core genome phylogeny.;In the second study, core genomes of Bacillus and Eudicot were determined individually from whole genome sequences of members of each genus, along with closely related species using BSRs. The Eudicot core genome was used as a control for evidence that results observed in the Bacillus core genomes were not due to horizontal gene transfer. Each core genome was analyzed with MrBayes and BUCKy to test the robustness of both approaches using sequences from different domains of life. Three multiple sequence alignments, ClustalW2, MUSCLE, and T-COFFEE, were used as inputs for MrBayes. Over 75% of all genes studied had a resolved gene tree topology after one of ten million generations of MrBayes, regardless of MSA. BUCKy calculated concordance trees for both core genomes. BUCKy tree topology was not affected by the MSAs. In both core genomes, high concordance factors were found on interior nodes, defining the relationship between groups of species. Outer nodes between outgroups had lower concordance factors, leading to the conclusion that genomes of more species would need to be included in order to resolve the phylogeny from more distant relatives.