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High-Resolution Comparison of Bacterial Conjugation Frequencies
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Distribution, diversity, and potential mobility of extrachromosomal elements related to the Bacillus anthracis pXO1

Xiaomin Hu1, Géraldine Van der Auwera, Sophie Timmery

  • 1Laboratory of Food and Environmental Microbiology, Université Catholique de Louvain, Croix du Sud 2/12, B-1348 Louvain-la-Neuve, Belgium.

Applied and Environmental Microbiology
|March 24, 2009
PubMed

Insights

The study found that pXO1 and pXO2-like plasmids in Bacillus cereus group strains can transfer genetic material. These plasmids, crucial for bacterial conjugation, showed flexibility in their transfer modules and active evolution.

Area of Science:

  • Microbiology
  • Genetics
  • Molecular Biology

Background:

  • Clinical isolates of Bacillus cereus and biopesticide Bacillus thuringiensis harbor pXO1 and pXO2-like plasmids.
  • Some pXO2-like plasmids, such as pBT9727 and pAW63, are known to be conjugative.

Purpose of the Study:

  • To analyze 1,000 B. cereus group isolates for pXO1 and pXO2-like replicons.
  • To investigate the presence of pXO2-related conjugative modules.
  • To determine the transfer potential and evolutionary dynamics of these plasmids.

Main Methods:

  • Screening of 1,000 B. cereus group isolates for pXO1 and pXO2-like replicons.
  • Detection of pXO2-related conjugative transfer module genes.
  • Plasmid size analysis and detection of Bacillus anthracis virulence genes.
  • Conjugation experiments to assess self-transfer and mobilization of small plasmids.
  • Analysis of group II introns and dendrograms for repA and virB4 genes.

Main Results:

  • pXO1 and pXO2-like replicons were found in 6.6% and 7.7% of environmental samples, respectively.
  • 1.54% of strains carried pXO2-like transfer module genes, exclusively in strains with a pXO2-like replicon.
  • No Bacillus anthracis toxin or capsule genes were detected in isolates with pXO1/pXO2-like plasmids.
  • 17 out of 22 pXO2-like plasmids with transfer modules demonstrated self-transfer and mobilized small plasmids.
  • Variations in group II introns and discrepancies in dendrograms indicated flexibility and active evolution of pXO2 plasmids.

Conclusions:

  • The presence of pXO1 and pXO2-like replicons is linked to conjugative transfer modules in B. cereus group strains.
  • pXO2-like plasmids exhibit significant flexibility in their conjugation modules and undergo active evolution.
  • The study highlights the dynamic nature of plasmid evolution and transfer in bacteria.

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