Genome Sequence of Bacillus anthracis STI, a Sterne-Like Georgian/Soviet Vaccine Strain

Abstract

The Bacillus anthracis strain STI is a Soviet vaccine strain that lacks the pXO2 plasmid. Previous data indicate that this isolate forms a new branch within the B. anthracis sub-group originally identified as A. Br.008/009.

GENOME ANNOUNCEMENT

Two distinct Soviet anthrax vaccine strains have been previously described. The first is a rare isolate that was sequenced by the J. Craig Venter Institute (JCVI) and is known as Bacillus anthracis strain Tsiankovskii-I (accession no. PRJNA54481). The GenBank entry for this genome indicates that this particular strain was used as an animal vaccine and is unusual because it contains both of the virulence plasmids of B. anthracis, pXO1 and pXO2. The second Soviet anthrax vaccine strain is the subject of this Genome Announcement. This strain is the more publicized Georgian/Soviet vaccine strain known as STI (1–4). The original vaccine was purportedly developed by Soviet Scientists in the 1940s at their Kirov Institute and was successfully used to vaccinate animals (2). A similar human anthrax vaccine of STI was produced in the Vaccine/Serum Institute, Tbilisi, Georgia (3, 4). This is a Sterne-like vaccine strain that lacks the pXO2 plasmid that accounts for the production of a poly-glutamate capsule layer, one of the virulence factors that define B. anthracis. Previous studies indicated that both of these isolates are on a specific sub-branch of B. anthracis that has been defined as the trans-Eurasian cluster (also A. Br.008/009) so named because the vast majority of >200 isolates from this sub-group in the B. anthracis collection at Northern Arizona University, were originally geo-located throughout Europe and China (5–7). The genome of the STI strain is therefore, distinct from the original Sterne vaccine strain and it is part of a new paraphyletic branch within the trans-Eurasian cluster. The precise strain that was sequenced has a designation BaA0485 in the Keim Laboratory archive and is also designated as STI-89 and K2789. This strain was provided by P. Turnbull.

Whole-genome shotgun sequencing (WGS) of the STI isolate (A0485; aka STI-89, K2789) was performed using the Illumina GAIIx sequencing platform. Following fragmentation to 500 bp insert sizes, end reparation, and sample tagging, the sequencer produced 4.45 million (genome) and 495,514 (pXO1 plasmid), 100-bp paired-end reads or coverage data at 87× and 256× for the genome and the pXO1 plasmid, respectively. Comparative assemblies were performed with both DNASTAR and CLC Bio Genomics Workbench (http://www.clcbio.com/) using the Ames ancestor reference genome (6) as a template. The conserved nature of the B. anthracis genome and the standard use of the Ames ancestor reference genome greatly facilitate the identification of unique regions in new assemblies. A de novo assembly was also performed using the paired-end sequence data with CLC Bio Genomics WorkBench and the resulting analysis yielded 126 contigs. Both the template and de novo assembled contigs were submitted to the RAST annotation server for subsystem classification and functional annotation (http://metagenomics.anl.gov/) (8).

Nucleotide sequence accession numbers.

The NCBI BioProject ID is PRJNA243052 and the GenBank accession numbers for this STI genome are BaA0485_chr (CP007660) and BaA0485_pXO1 (CP007661).