A Secreted Factor Coordinates Environmental Quality With Bacillus Development

PLoS One. 2015 Dec 11;10(12):e0144168. doi: 10.1371/journal.pone.0144168. eCollection 2015.


Entry into sporulation is governed by the master regulator Spo0A. Spo0A accumulates in its active form, Spo0A-P, as cells enter stationary phase. Prior reports have shown that the acute induction of constitutively active Spo0A during exponential growth does not result in sporulation. However, a subsequent study also found that a gradual increase in Spo0A-P, mediated through artificial expression of the kinase, KinA, during exponential growth, is sufficient to trigger sporulation. We report here that sporulation via KinA induction depends on the presence of an extracellular factor or factors (FacX) that only accumulates to active levels during post-exponential growth. FacX is retained by dialysis with a cutoff smaller than 500 Dalton, can be concentrated, and is susceptible to proteinase K digestion, similar to described quorum-sensing peptides shown to be involved in promoting sporulation. However, unlike previously characterized peptides, FacX activity does not require the Opp or App oligopeptide transporter systems. In addition, FacX activity does not depend on SigH, Spo0A, or ComX. Importantly, we find that in the presence of FacX, B. subtilis can be induced to sporulate following the artificial induction of constitutively active Spo0A. These results indicate that there is no formal requirement for gradual Spo0A-P accumulation and instead support the idea that sporulation requires both sufficient levels of active Spo0A and at least one other signal or condition.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Bacillus / drug effects
  • Bacillus / growth & development*
  • Bacillus / metabolism*
  • Bacterial Proteins / metabolism*
  • Culture Media, Conditioned / pharmacology
  • Dialysis
  • Endopeptidase K / metabolism
  • Environment*
  • Membrane Transport Proteins / metabolism
  • Membranes, Artificial
  • Molecular Weight
  • Peptides / metabolism
  • Spores, Bacterial / drug effects
  • Spores, Bacterial / metabolism


  • Bacterial Proteins
  • Culture Media, Conditioned
  • Membrane Transport Proteins
  • Membranes, Artificial
  • Peptides
  • Endopeptidase K

Grant support

This work was funded by start-up funding to JKH from Texas A&M University and the Center for Phage Technology at Texas A&M University. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.