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ORIGINAL RESEARCH article

Front. Microbiol.
Sec. Infectious Agents and Disease
Volume 16 - 2025 | doi: 10.3389/fmicb.2025.1527049
This article is part of the Research Topic Bacterial Pathogens and Virulence Factor Genes: Diversity and Evolution View all 11 articles

Decoding the anomalies: A genome-based analysis of Bacillus cereus group strains closely related to Bacillus anthracis

Provisionally accepted
Thuto Gomolemo Magome Thuto Gomolemo Magome 1*Marius Surleac Marius Surleac 2Ayesha Hassim Ayesha Hassim 3Cornelius Carlos Bezuidenhout Cornelius Carlos Bezuidenhout 1Henriette Van Heerden Henriette Van Heerden 3Kgaugelo Edward Lekota Kgaugelo Edward Lekota 1
  • 1 North-West University, Potchefstroom, South Africa
  • 2 Research Institute, University of Bucharest, Bucharest, Romania
  • 3 Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa

The final, formatted version of the article will be published soon.

    The Bacillus cereus group encompasses a complex group of closely related pathogenic and non-pathogenic bacterial species. Key members include B. anthracis, B. cereus, and B. thuringiensis organisms that, despite genetic proximity, diverge significantly in morphology and pathogenic potential. Taxonomic challenges persist due to inconsistent classification methods, particularly for B. cereus isolates that resemble B. anthracis in genetic clustering. This study investigated B. cereus group isolates from blood smears of animal carcasses in Kruger National Park, uncovering an unusual isolate with B. cereus features based on classical microbiological tests yet B. anthracis-like genomic similarities with an Average Nucleotide Identity (ANI) of ³95%. Using comparative genomics, pan-genomics and whole genome Single Nucleotide Polymorphism (wgSNP) analysis, a total of 103 B. cereus group genomes were analysed, including nine newly sequenced isolates from South Africa and a collection of isolates that showed some classification discrepancies, thus classified as 'anomalous'. Of the 36 strains identified as B. anthracis in GenBank, 26 clustered phylogenetically with the four confirmed B. anthracis isolates from South Africa and shared 99% ANI. Isolates with less than 99% ANI alignment to B. anthracis exhibited characteristics consistent with B. cereus and/or B. thuringiensis, possessing diverse genetic profiles, insertion elements, resistance genes, and virulence genes features, contrasting with the genetic uniformity of typical B. anthracis. The findings underscore a recurrent acquisition of mobile genetic elements within B. cereus and B. thuringiensis, a process infrequent in B. anthracis. This study highlights the pressing need for standardized taxonomic criteria in B. cereus group classification, especially as anomalous isolates emerge. This study suggests that the nomenclature framework of Carroll et al. (2020) offers an effective solution for classifying species into genomospecies groups. We recommend isolates with ANI ³99% to standard reference B. anthracis be designated as typical B. anthracis in GenBank to maintain taxonomic clarity and precision.

    Keywords: Bacillus cereus group, Bacillus anthracis, whole genome sequencing, Pan-genomics, ANI (average nucleotide identity)

    Received: 12 Nov 2024; Accepted: 15 Jan 2025.

    Copyright: © 2025 Magome, Surleac, Hassim, Bezuidenhout, Van Heerden and Lekota. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Thuto Gomolemo Magome, North-West University, Potchefstroom, South Africa

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