Osmotic strength blocks sporulation at stage II by impeding activation of early sigma factors in Bacillus subtilis

Curr Microbiol. 1998 Feb;36(2):75-9. doi: 10.1007/s002849900282.


In Bacillus subtilis, osmotolerance is a stationary phase-dependent, adaptive response inhibiting sporulation and sharing common regulators with this process. The extent of this inhibition was determined by measuring transcription activity of promoter lacZ fusions to early sigma genes (spoIIG and spoIIA coding for precursors of sigmaE and sigmaF) and to reporters of them (spoIID, spoIIQ and spoIIIG), in the absence and presence of 0.6 M or 1 M NaCl. The transcription activity of these sigma precursors, normally occurring at the onset of the stationary phase, was reduced to 30-50% of their maximal expression in hyperosmotic conditions; expression of genes under their control was, however, more inhibited (<10%). Therefore, sporulation was blocked at the sigma sigmaE and sigmaF activation steps. This assumption was confirmed by electron microscopic examinations of hyperosmotic cultures, which presented asymmetric septa characteristic of stage II mutants. Discussion was focused on the particular composition and/or structure of membranes during hyperosmotic growth and their involvement in the arrest of sporulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus subtilis / chemistry
  • Bacillus subtilis / genetics
  • Bacillus subtilis / physiology*
  • Bacterial Proteins / drug effects
  • Bacterial Proteins / genetics*
  • Gene Expression / drug effects
  • Gene Expression / genetics
  • Gene Expression Regulation / drug effects
  • Gene Expression Regulation / genetics
  • Genes, Bacterial / drug effects
  • Genes, Bacterial / genetics
  • Microscopy, Electron
  • Osmolar Concentration
  • Sigma Factor / genetics*
  • Sodium Chloride / administration & dosage
  • Sodium Chloride / pharmacology
  • Spores
  • Spores, Bacterial / drug effects
  • Spores, Bacterial / physiology
  • Spores, Bacterial / ultrastructure
  • Time Factors
  • Transcription Factors*


  • Bacterial Proteins
  • Sigma Factor
  • Transcription Factors
  • spoIIR protein, Bacillus subtilis
  • spore-specific proteins, Bacillus
  • Sodium Chloride