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Acid tolerance in Rhizobium meliloti strain WSM419 involves a two-component sensor-regulator system
R P Tiwari1, W G Reeve, M J Dilworth
1Nitrogen Fixation Research Group, School of Biological and Environmental Sciences, Murdoch University, Australia.
Microbiology (Reading, England)
|July 1, 1996
Summary
Rhizobium meliloti uses a two-component system, ActRS, to sense and respond to acidic conditions. This system is crucial for maintaining acid tolerance in these important soil bacteria.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Physiology
Background:
- Rhizobium meliloti is a soil bacterium important for nitrogen fixation.
- Acid sensitivity can limit bacterial growth and function in certain environments.
- Two-component systems are common signal transduction mechanisms in prokaryotes.
Purpose of the Study:
- To identify the genetic basis of acid sensitivity in Rhizobium meliloti.
- To characterize the role of a novel two-component system in bacterial acid tolerance.
Main Methods:
- Tn5 mutagenesis was used to generate an acid-sensitive mutant.
- DNA sequencing and analysis identified two open reading frames, actS and actR.
- Complementation studies and gene expression analysis (beta-galactosidase assays) were performed.
Main Results:
- A Tn5-induced mutant, TG5-46, exhibited acid sensitivity below pH 6.0.
- The identified genes, actS and actR, show similarity to sensor-regulator proteins of two-component systems.
- Disruption of actS caused acid sensitivity, and both actS and actR were required for full acid tolerance.
- Both genes were constitutively expressed across different pH levels.
Conclusions:
- A two-component sensor-regulator protein pair, ActRS, is implicated in acid tolerance in Rhizobium meliloti.
- ActRS likely plays a role in pH sensing and response mechanisms in these bacteria.