Pan-genome analysis of Senegalese and Gambian strains of Bacillus anthracis

Abstract

Bacillus anthracis is the causative agent of anthrax, and it is classified as “category A” biological weapon. There were six available complete genomes (A0248, Ames, Ames Ancestor, CDC684, H0491 and Sterne). Here, one Gambian and two Senegalese strains (Gmb1, Sen2Col2 and Sen3) were added. In this work, the pan-genome of B. anthracis was studied based on nine strains and using bioinformatics tools as Cluster of Orthologous Groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Thereafter, B. anthracis pan-genome having 2893 core genes and 85 accessory genes was estimated. With Mauve method, the pan-genome of B. anthracis was verified and it was found to be very narrow and clonal. To have confidence in this study, different tools were used to compare and validate the results. All of the tools yielded the same results; the addition of the Senegalese and Gambian strains did not change the nature of the B. anthracis pan-genome (2893 core genes and 85 accessory genes), which had a core/pan-genome ratio of 99%. The closed nature of the pan-genome of B. anthracis (the core genome) represents 99% of the pan-genome size. The hypothesis that B. anthracis had a closed pan-genome was hereby validated.

Key words: Bacillus anthracis, Senegalese, Gambian strains, pan-genome.