Extracellular DNA release by undomesticated Bacillus subtilis is regulated by early competence

PLoS One. 2012;7(11):e48716. doi: 10.1371/journal.pone.0048716. Epub 2012 Nov 2.

Abstract

Extracellular DNA (eDNA) release is a widespread capacity described in many microorganisms. We identified and characterized lysis-independent eDNA production in an undomesticated strain of Bacillus subtilis. DNA fragments are released during a short time in late-exponential phase. The released eDNA corresponds to whole genome DNA, and does not harbour mutations suggesting that is not the result of error prone DNA synthesis. The absence of eDNA was linked to a spread colony morphology, which allowed a visual screening of a transposon library to search for genes involved in its production. Transposon insertions in genes related to quorum sensing and competence (oppA, oppF and comXP) and to DNA metabolism (mfd and topA) were impaired in eDNA release. Mutants in early competence genes such as comA and srfAA were also defective in eDNA while in contrast mutations in late competence genes as those for the DNA uptake machinery had no effect. A subpopulation of cells containing more DNA is present in the eDNA producing strains but absent from the eDNA defective strain. Finally, competent B. subtilis cells can be transformed by eDNA suggesting it could be used in horizontal gene transfer and providing a rationale for the molecular link between eDNA release and early-competence in B. subtilis that we report.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus subtilis / genetics*
  • Bacterial Proteins / genetics
  • Biofilms
  • Cloning, Molecular
  • DNA / metabolism
  • DNA Transposable Elements / genetics
  • DNA, Bacterial / genetics
  • Deoxyribonuclease I / metabolism
  • Escherichia coli Proteins / metabolism
  • Flow Cytometry / methods
  • Gene Library
  • Gene Transfer, Horizontal
  • Mutagenesis
  • Mutation
  • Phenotype
  • Plasmids / metabolism
  • Ribosomal Proteins / metabolism
  • Temperature

Substances

  • Bacterial Proteins
  • DNA Transposable Elements
  • DNA, Bacterial
  • Escherichia coli Proteins
  • Ribosomal Proteins
  • ribosomal protein S1, E coli
  • DNA
  • Deoxyribonuclease I

Grants and funding

Funding was provided by the Metagenome of the Iberian Peninsula, CONSOLIDER project (Spain government funding), reference: CSD200700005. M.L. was supported by a Rafael Calvo Rodés fellowship from INTA. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.