Cloning and sequence analysis ofAlcaligenes faecalis nifHDK gene cluster

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Nitrogen fixation is crucial for plant growth and ecosystem health.
• Understanding the genetic basis of nitrogen fixation in bacteria like Alcaligenes faecalis is essential.

Purpose of the Study:

• To identify and characterize the nitrogenase (nifHDK) genes in Alcaligenes faecalis.
• To analyze the genetic structure and regulatory elements of these genes.

Main Methods:

• DNA hybridization using nifH and nifHD probes from Klebsiella pneumoniae.
• Cloning of the homologous fragment into pBluescript SK(+) plasmid.
• Physical mapping, subcloning, and DNA sequencing of the insert.
• Bioinformatic analysis of gene sequences and regulatory regions.

Main Results:

• A 4.6 kb fragment homologous to nifH was identified and cloned.
• The Alcaligenes faecalis nifHDK homology contained a Sigma(54)-dependent promoter with UAS and A-T rich regions.
• The nifH and nifD open reading frames (ORFs) were 888 bp and 1476 bp, respectively.
• High GC content (61.6% and 60.0%) and conserved motifs were observed in nifH and nifD.
• The deduced amino acid sequences showed high homology to other nitrogen-fixing bacteria, particularly with Alcaligenes eutrophus.

Conclusions:

• Alcaligenes faecalis possesses a functional nitrogenase gene cluster with conserved regulatory elements.
• The genetic organization and sequence homology suggest a significant role in nitrogen fixation.
• The findings provide insights into the evolution and diversity of nitrogen fixation genes in bacteria.