Competition between nitrate and nitrite reduction in denitrification by Pseudomonas fluorescens
J S Almeida1, M A Reis, M J Carrondo
1Chemistry Department, Faculdade de Ciencias e Tecnologia/UNL, 2825 Monte de Caprica, Portugal.
Biotechnology and Bioengineering
|June 5, 1995
Summary
Denitrification kinetics in Pseudomonas fluorescens show that nitrate and nitrite reduction compete for electron donors. Optimal pH for both processes is 7.0, with nitrite accumulation influenced by pH.
Area of Science:
- Microbiology
- Environmental Science
- Biochemistry
Background:
- Denitrification is a crucial microbial process in nitrogen cycling.
- Understanding the kinetics of denitrification is vital for environmental remediation and agricultural applications.
- Pseudomonas fluorescens serves as a model organism for studying bacterial denitrification.
Purpose of the Study:
- To investigate the kinetics of denitrification in Pseudomonas fluorescens.
- To determine the influence of pH on nitrate and nitrite reduction rates.
- To develop a kinetic model for competitive inhibition in denitrification.
Main Methods:
- Utilized pure cultures of Pseudomonas fluorescens under anoxic conditions.
- Assayed denitrification rates at various pH values (6.6-7.8) and temperatures (28°C).
- Applied Michaelis-Menten kinetics to model nitrate and nitrite reduction, considering competitive inhibition.
Main Results:
- Nitrate and nitrite reduction rates were dependent on substrate concentrations and competed for common electron donors.
- The optimal pH for both nitrate and nitrite reduction was 7.0.
- Nitrite accumulation was pH-dependent, decreasing significantly at pH 7.8, despite constant maximum reduction rates.
Conclusions:
- A kinetic model for competitive inhibition of nitrite reduction by nitrate was proposed and validated.
- The regulation of electron flow between reductases is reversible and pH-dependent.
- Environmental factors like pH significantly impact denitrification efficiency and intermediate accumulation.
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