Isolation and complete sequence of the purL gene encoding FGAM synthase II in Lactobacillus casei

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Purine biosynthesis is essential for all living organisms.
• The de novo purine synthesis pathway involves multiple enzymes.
• Gene organization can vary significantly between bacterial species.

Purpose of the Study:

• To clone and sequence the purL gene from Lactobacillus casei.
• To analyze the genetic organization of purine biosynthesis genes in L. casei.
• To compare the purL gene and its surrounding genes with homologous genes in other bacteria.

Main Methods:

• Gene cloning and DNA sequencing.
• Bioinformatic analysis of nucleotide and amino acid sequences.
• Comparative genomics.

Main Results:

• The Lactobacillus casei purL gene was successfully cloned and sequenced, encoding phosphoribosylformylglycinamidine synthase II.
• The putative purL product shares 25% and 53% identity with homologous enzymes from Escherichia coli and Bacillus subtilis, respectively.
• L. casei purL, purQ, purF, and purC genes are organized in an operon, similar to B. subtilis, contrasting with the scattered arrangement in E. coli and Salmonella typhimurium.

Conclusions:

• The purL gene and its associated genes in L. casei are organized in an operon structure.
• This operon organization is conserved in B. subtilis but differs from the genomic arrangement in E. coli and S. typhimurium.
• The findings provide insights into the evolutionary divergence of purine biosynthesis gene clusters in bacteria.