Complete genome of Bacillus anthracis strain ter21 from an infected zoo pony in Ternopil, Ukraine, 2021.

Overview

• This study presents the complete genome sequencing and analysis of Bacillus anthracis strain ter21, isolated from a fatal anthrax case in a zoo pony in Ternopil, Ukraine, in 2021.
• The researchers used rapid nanopore sequencing technology to assemble the entire bacterial genome and identify important virulence factors.

Introduction and Background

• Bacillus anthracis is the bacterial pathogen responsible for anthrax, a serious infectious disease that can affect animals and humans.
• The bacteria typically harbor two key virulence plasmids: pXO1 and pXO2, which are essential for its pathogenicity.
• Understanding the genetic makeup and presence of these plasmids in specific isolates helps in epidemiological tracking and understanding outbreaks.
• This study focuses on a particular strain, named ter21, isolated from an infected pony at a zoo in Ternopil, Ukraine.

Methods

• The research team employed rapid nanopore whole-genome sequencing, a modern sequencing technology capable of reading long stretches of DNA quickly.
• This method allowed for the near real-time assembly of the bacterial genome, enabling prompt analysis of the pathogen.
• Genome assembly involved sequencing the entire chromosomal DNA plus any plasmids present within the strain.

Results

• The complete genome of strain ter21 was successfully assembled, totaling 5,229,480 base pairs (bp).
• Phylogenetic analysis assigned this strain to the Tsiankovskii-I group of Bacillus anthracis, contributing to strain classification and understanding of regional diversity.
• Critically, both major virulence plasmids were identified:
  • pXO1, which carries genes encoding the anthrax toxin responsible for severe disease symptoms.
  • pXO2, which is involved in capsule formation, helping the bacteria evade the host immune system.
• The detection of these plasmids confirms the isolate’s potential to cause severe anthrax infection.

Significance

• This work demonstrates the utility of rapid nanopore sequencing for pathogen genome assembly directly from outbreak samples.
• Having detailed genomic information aids in understanding anthrax outbreaks, tracking the spread, and developing targeted responses.
• Specifically, identifying the presence of key virulence factors helps confirm the strain’s pathogenic potential and may guide public health interventions, especially in zoonotic contexts such as zoo animals.
• The data also contribute to the global genetic database of Bacillus anthracis strains, which is valuable for epidemiological studies and vaccine development.