Mokgokong Sankwetea P, Hassim Ayesha, Mafuna Tendo, Turner Wendy C, van Heerden Henriette, Lekota Kgaugelo E
Department of Veterinary Tropical Diseases, University of Pretoria Veterinary Campus, Onderstepoort, South Africa; Unit of Environmental Sciences and Management, North-West University, Potchefstroom, South Africa.
Department of Veterinary Tropical Diseases, University of Pretoria Veterinary Campus, Onderstepoort, South Africa.
Genomics. 2025 Sep;117(5):111074. doi: 10.1016/j.ygeno.2025.111074. Epub 2025 Jul 7.
Bacillus anthracis, the causative agent of anthrax, is composed of three genetic clades (A, B, and C). Clade-A is the most common and distributed worldwide, B-clade has a narrow geographic distribution, and C-clade is rare. South Africa's Kruger National Park (KNP) has high diversity of B. anthracis, with strains from A and B clades described from its northernmost region, Pafuri. We employed whole genome sequencing to investigate the genomic diversity of B. anthracis strains isolated from animal carcasses (n = 34) during the 2012-2015 outbreaks. Whole-genome single-nucleotide polymorphism (wgSNP) analysis assigned the 2012-2015 B. anthracis genomes to the A-clade branch, distributed across the branch's two minor sub-clades A.Br.005/006. Additionally, pan-genomic analysis distinguished the A- and B-clade genomes, identifying unique accessory genes. Notable genetic differences include the biosynthetic spore cell wall genes; long-chain fatty acid CoA ligases (FaD13), Bacillus collagen-like protein of anthracis (BclA) involved in the exosporium germination, as well as a truncated murein DD-endopeptidase (mepH) found in the pXO2 plasmid of the B-clade strains. The tryptophan synthase subunit alpha gene (trpA), which results in a pseudogene in B-clade genomes separates the A- and B-clade genomes. These differences in biosynthetic cell wall genes suggest variation in adaptability or cell growth of the B-clade strains in the environment, further influenced by the truncation of the trpA gene involved in spore germination. The A.Br.005/006-clade strains in KNP exhibit higher genetic diversity, which may enhance their resilience to environmental stressors. In contrast, the KNP B-clade (B.Br.001/002) strains show limited genetic variation, potentially reducing their adaptability. This pattern is evident through whole-genome SNP analysis and pan-genomics investigating the evolution of B. anthracis.
炭疽杆菌是炭疽病的病原体，由三个遗传分支（A、B和C）组成。A分支最为常见，分布于全球；B分支的地理分布范围狭窄；C分支则很罕见。南非的克鲁格国家公园（KNP）拥有高度多样的炭疽杆菌，在其最北部地区帕富里发现了来自A和B分支的菌株。我们利用全基因组测序来研究2012年至2015年疫情期间从动物尸体（n = 34）分离出的炭疽杆菌菌株的基因组多样性。全基因组单核苷酸多态性（wgSNP）分析将2012年至2015年的炭疽杆菌基因组归入A分支，分布在该分支的两个较小亚分支A.Br.005/006中。此外，泛基因组分析区分了A和B分支的基因组，识别出独特的辅助基因。显著的遗传差异包括生物合成孢子细胞壁基因；长链脂肪酸辅酶A连接酶（FaD13）、参与芽孢外壁萌发的炭疽杆菌胶原样蛋白（BclA），以及在B分支菌株的pXO2质粒中发现的截短型胞壁质DD-内肽酶（mepH）。色氨酸合酶亚基α基因（trpA）在B分支基因组中导致假基因的产生，这将A和B分支的基因组区分开来。这些生物合成细胞壁基因的差异表明B分支菌株在环境中的适应性或细胞生长存在差异，这进一步受到参与孢子萌发的trpA基因截短的影响。克鲁格国家公园的A.Br.005/006分支菌株表现出更高的遗传多样性，这可能增强它们对环境压力的恢复力。相比之下，克鲁格国家公园的B分支（B.Br.001/002）菌株显示出有限的遗传变异，可能会降低它们的适应性。通过全基因组SNP分析和泛基因组学研究炭疽杆菌的进化，这种模式很明显。
