Stress responses of the industrial workhorse Bacillus licheniformis to osmotic challenges

PLoS One. 2013 Nov 15;8(11):e80956. doi: 10.1371/journal.pone.0080956. eCollection 2013.

Abstract

The Gram-positive endospore-forming bacterium Bacillus licheniformis can be found widely in nature and it is exploited in industrial processes for the manufacturing of antibiotics, specialty chemicals, and enzymes. Both in its varied natural habitats and in industrial settings, B. licheniformis cells will be exposed to increases in the external osmolarity, conditions that trigger water efflux, impair turgor, cause the cessation of growth, and negatively affect the productivity of cell factories in biotechnological processes. We have taken here both systems-wide and targeted physiological approaches to unravel the core of the osmostress responses of B. licheniformis. Cells were suddenly subjected to an osmotic upshift of considerable magnitude (with 1 M NaCl), and their transcriptional profile was then recorded in a time-resolved fashion on a genome-wide scale. A bioinformatics cluster analysis was used to group the osmotically up-regulated genes into categories that are functionally associated with the synthesis and import of osmostress-relieving compounds (compatible solutes), the SigB-controlled general stress response, and genes whose functional annotation suggests that salt stress triggers secondary oxidative stress responses in B. licheniformis. The data set focusing on the transcriptional profile of B. licheniformis was enriched by proteomics aimed at identifying those proteins that were accumulated by the cells through increased biosynthesis in response to osmotic stress. Furthermore, these global approaches were augmented by a set of experiments that addressed the synthesis of the compatible solutes proline and glycine betaine and assessed the growth-enhancing effects of various osmoprotectants. Combined, our data provide a blueprint of the cellular adjustment processes of B. licheniformis to both sudden and sustained osmotic stress.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus / drug effects
  • Bacillus / metabolism*
  • Betaine / pharmacology
  • Gene Expression Regulation, Bacterial / drug effects
  • Osmotic Pressure / drug effects
  • Oxidative Stress / drug effects

Substances

  • Betaine

Grants and funding

This study was financially supported by grants from the German Ministry of Education and Research via the Bacell-SysMo2 consortium (to ML, MH and EB) and the competence network “Genome Research in Bacteria” (to ML, MH, KHM and TS). Additional Funds were provided through the LOEWE program of the State of Hessen (via the Centre for Synthetic Microbiology; SynMicro, Marburg) (to EB), the Fonds der Chemischen Industrie (to EB) and the French National Centre for Scientific Research (UPR 9073), Université Paris VII-Denis Diderot (to HP). The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.