Timing of Induction of Osmotically Controlled Genes in Salmonella enterica Serovar Typhimurium, Determined with Quantitative Real-Time Reverse Transcription-PCR
Open Access
- 1 December 2005
- journal article
- Published by American Society for Microbiology in Applied and Environmental Microbiology
- Vol. 71 (12), 8273-8283
- https://doi.org/10.1128/aem.71.12.8273-8283.2005
Abstract
The signals that control the transcription of osmoregulated genes are not understood satisfactorily. The “turgor control model” suggested that the primary osmoregulatory signal in Enterobacteriaceae is turgor loss, which induces the kdp K+ transport operon and activates the Trk K+ permease. The ensuing increase in cytoplasmic K+ concentration was proposed to be the signal that turns on all secondary responses, including the induction of the proU (proline-glycine betaine transport) operon. The “ionic strength model” proposed that the regulatory signal for all osmotically controlled responses is the increase in the cytoplasmic ionic strength or macromolecular crowding after an osmotic upshift. The assumption in the turgor control model that the induction of kdp is a primary response to osmotic shock predicts that this response should precede all secondary responses. Both models predict that the induction of all osmotically activated responses should be independent of the chemical nature of the solute used to impose osmotic stress. We tested these predictions by quantitative real-time reverse transcription-PCR analysis of the expression of six osmotically regulated genes in Salmonella enterica serovar Typhimurium. After shock with 0.3 M NaCl, proU was induced at 4 min, proP and rpoS were induced at 4 to 6 min, kdp was induced at 8 to 9 min, and otsB and ompC were induced at 10 to 12 min. After an equivalent osmotic shock with 0.6 M sucrose, proU was induced with kinetics similar to those seen with NaCl, but induction of kdp was reduced 150-fold in comparison to induction by NaCl. Our results are inconsistent with both the turgor control and the ionic strength control models.Keywords
This publication has 59 references indexed in Scilit:
- MicC, a Second Small-RNA Regulator of Omp Protein Expression inEscherichia coliJournal of Bacteriology, 2004
- Interfering with Different Steps of Protein SynthesisExplored by Transcriptional Profiling of Escherichia coli K-12Journal of Bacteriology, 2003
- Osmosensor ProP of Escherichia coli Responds to the Concentration, Chemistry, and Molecular Size of Osmolytes in the Proteoliposome Lumen,Biochemistry, 2002
- From acids to osmZ: multiple factors influence synthesis of the OmpF and OmpC porins in Escherichia coliMolecular Microbiology, 1996
- Signal‐sensing mechanisms of the putative osmosensor KdpD in Escherichia coliMolecular Microbiology, 1994
- Immediate and transient inhibition of the respiration ofEscherichia coliunder hyperosmotic shockFEMS Microbiology Letters, 1994
- PROKARYOTIC OSMOREGULATION: Genetics and PhysiologyAnnual Review of Microbiology, 1991
- Enteric bacteria and osmotic stress: Intracellular potassium glutamate as a secondary signal of osmotic stress?FEMS Microbiology Letters, 1990
- Osmotic regulation of gene expression: ionic strength as an intracellular signal?Trends in Biochemical Sciences, 1987
- Osmoregulation by potassium transport inEscherichia coliFEMS Microbiology Letters, 1986