Bacillus Anthracis Comparative Genome Analysis in Support of the Amerithrax Investigation

TitleBacillus Anthracis Comparative Genome Analysis in Support of the Amerithrax Investigation
Publication TypeJournal Articles
Year of Publication2011
AuthorsRasko DA, Worsham PL, Abshire TG, Stanley ST, Bannan JD, Wilson MR, Langham RJ, Decker SR, Jiang L, Read TD, Phillippy AM, Salzberg SL, Pop M, Van Ert MN, Kenefic LJ, Keim PS, Fraser-Liggett CM, Ravel J
JournalProceedings of the National Academy of SciencesPNAS
Pagination5027 - 5032
Date Published2011/03/22/
ISBN Number0027-8424, 1091-6490

Before the anthrax letter attacks of 2001, the developing field of microbial forensics relied on microbial genotyping schemes based on a small portion of a genome sequence. Amerithrax, the investigation into the anthrax letter attacks, applied high-resolution whole-genome sequencing and comparative genomics to identify key genetic features of the letters’ Bacillus anthracis Ames strain. During systematic microbiological analysis of the spore material from the letters, we identified a number of morphological variants based on phenotypic characteristics and the ability to sporulate. The genomes of these morphological variants were sequenced and compared with that of the B. anthracis Ames ancestor, the progenitor of all B. anthracis Ames strains. Through comparative genomics, we identified four distinct loci with verifiable genetic mutations. Three of the four mutations could be directly linked to sporulation pathways in B. anthracis and more specifically to the regulation of the phosphorylation state of Spo0F, a key regulatory protein in the initiation of the sporulation cascade, thus linking phenotype to genotype. None of these variant genotypes were identified in single-colony environmental B. anthracis Ames isolates associated with the investigation. These genotypes were identified only in B. anthracis morphotypes isolated from the letters, indicating that the variants were not prevalent in the environment, not even the environments associated with the investigation. This study demonstrates the forensic value of systematic microbiological analysis combined with whole-genome sequencing and comparative genomics.