Ammonification in Bacillus subtilis utilizing dissimilatory nitrite reductase is dependent on resDE

Area of Science:

• Microbiology
• Biochemistry
• Molecular Biology

Background:

• Bacillus subtilis is known to perform anaerobic nitrate respiration.
• The complete reduction pathway of nitrate to ammonia in B. subtilis has not been fully elucidated.
• Understanding microbial respiration pathways is crucial for environmental and biotechnological applications.

Purpose of the Study:

• To investigate the anaerobic respiratory pathway of Bacillus subtilis.
• To identify the enzymes and regulatory mechanisms involved in nitrite reduction.
• To determine if B. subtilis produces denitrification products.

Main Methods:

• Anaerobic growth experiments with varying electron acceptors.
• Enzyme activity assays using cell extracts and specific electron donors/acceptors.
• Genetic analysis involving gene mutations (nitrate reductase, resDE, fnr).

Main Results:

• Bacillus subtilis reduces nitrate to ammonia anaerobically, with no observed denitrification products.
• Both wild-type and nitrate reductase mutant strains grew anaerobically with nitrite as an electron acceptor.
• Oxygen-sensitive dissimilatory nitrite reductase activity was detected and found to be dependent on the resDE regulatory system.
• Mutation of the Fnr regulatory gene did not affect nitrite reductase formation.

Conclusions:

• Bacillus subtilis performs complete reduction of nitrate to ammonia under anaerobic conditions.
• A resDE-dependent nitrite reductase is involved in the anaerobic respiration of B. subtilis.
• The Fnr protein is not essential for the expression of this nitrite reductase activity.