DksA, ppGpp, and RegAB Regulate Nitrate Respiration in Paracoccus denitrificans
1Department of Biological Sciences, University of Texas at Dallas, Richardson, Texas, USA.
Journal of Bacteriology
|March 15, 2023
Summary
The study identifies key regulators, including ppGpp and DksA1, that control nitrate reductase expression in Paracoccus denitrificans, crucial for understanding denitrification and nitrogen cycling.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Paracoccus denitrificans utilizes periplasmic (NAP) and membrane-associated (Nar) nitrate reductases for nitrate reduction under aerobic and anaerobic conditions, respectively.
- NAP expression increases with reduced carbon sources like butyrate, suggesting a role in redox homeostasis.
- Denitrification in P. denitrificans is vital for nitrogen cycling and produces greenhouse gases.
Purpose of the Study:
- To elucidate the genetic and molecular mechanisms regulating NAP expression in P. denitrificans.
- To identify the roles of DksA homologs and RelA/SpoT in NAP gene regulation.
- To investigate the function of the RegAB two-component system in nitrate reductase expression.
Main Methods:
- Gene deletion studies of dksA1 and relA/spoT.
- Analysis of NAP promoter activity and enzyme activity.
- Exposure to protein synthesis inhibitors to induce ppGpp synthesis.
- Investigation of RegAB function under anaerobic conditions.
- Assessment of synthetic lethality between dksA1 and relA/spoT mutants.
Main Results:
- Deletion of dksA1 or relA/spoT abolished the butyrate-dependent increase in NAP expression.
- ppGpp, in conjunction with DksA1, mediates increased NAP gene expression.
- Protein synthesis inhibition triggered increased NAP promoter activity, supporting the ppGpp signaling model.
- RegAB negatively regulates NAP and positively regulates Nar expression under anaerobic growth.
- dksA1 and relA/spoT exhibit conditional synthetic lethality, impacting growth on reduced substrates.
Conclusions:
- ppGpp and DksA1 are critical regulators of NAP expression in response to reduced substrates.
- The RegAB system fine-tunes nitrate reductase expression during anaerobic respiration.
- Understanding these regulatory pathways is essential for controlling denitrification and its environmental impact.
Keywords:
DksAParacoccus denitrificansRegABguanosine tetraphosphatenitrate respirationredox homeostasisMore Related Videos
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