Redundancy and modularity in membrane-associated dissimilatory nitrate reduction in Bacillus

Area of Science:

• Microbiology
• Genomics
• Biochemistry

Background:

• The genus Bacillus includes species capable of denitrification, a crucial microbial process in nitrogen cycling.
• Understanding the genetic and biochemical basis of denitrification in Gram-positive bacteria like Bacillus is essential for ecological and biotechnological applications.

Purpose of the Study:

• To sequence the genomes of two denitrifying Bacillus type strains and reconstruct their dissimilatory nitrate reduction pathways.
• To investigate the mechanisms of denitrification in Bacillus, focusing on electron transfer and enzyme systems.

Main Methods:

• Whole-genome sequencing of Bacillus azotoformans LMG 9581(T) and Bacillus bataviensis LMG 21833(T).
• Bioinformatic reconstruction and analysis of dissimilatory nitrate reduction pathways.
• Identification and characterization of genes encoding key enzymes involved in denitrification.

Main Results:

• Denitrification pathways in Bacillus appear analogous to Gram-negative organisms, occurring in the periplasmic space with membrane-bound proteins.
• Functional redundancy and significant differences in denitrification pathways were observed between the two strains.
• Evidence for a novel nitric oxide reductase (NOR) was identified, in addition to the known menaquinol/cyt c-dependent NOR.
• Both strains possess two parallel pathways for nitrite reduction, enabling both denitrification and ammonification.

Conclusions:

• Bacillus species exhibit sophisticated denitrification mechanisms with unique features, including branched electron transfer and novel enzyme systems.
• The presence of dual nitrite reduction pathways allows these bacteria to adapt to diverse environmental conditions, functioning as both denitrifiers and ammonifiers.