Transcriptional and Functional Analysis of Oxalyl-Coenzyme A (CoA) Decarboxylase and Formyl-CoA Transferase Genes from Lactobacillus acidophilus

Abstract

Oxalic acid is found in dietary sources (such as coffee, tea, and chocolate) or is produced by the intestinal microflora from metabolic precursors, like ascorbic acid. In the human intestine, oxalate may combine with calcium, sodium, magnesium, or potassium to form less soluble salts, which can cause pathological disorders such as hyperoxaluria, urolithiasis, and renal failure in humans. In this study, an operon containing genes homologous to a formyl coenzyme A transferase gene (frc) and an oxalyl coenzyme A decarboxylase gene (oxc) was identified in the genome of the probiotic bacterium Lactobacillus acidophilus. Physiological analysis of a mutant harboring a deleted version of the frc gene confirmed that frc expression specifically improves survival in the presence of oxalic acid at pH 3.5 compared with the survival of the wild-type strain. Moreover, the frc mutant was unable to degrade oxalate. These genes, which have not previously been described in lactobacilli, appear to be responsible for oxalate degradation in this organism. Transcriptional analysis using cDNA microarrays and reverse transcription-quantitative PCR revealed that mildly acidic conditions were a prerequisite for frc and oxc transcription. As a consequence, oxalate-dependent induction of these genes occurred only in cells first adapted to subinhibitory concentrations of oxalate and then exposed to pH 5.5. Where genome information was available, other lactic acid bacteria were screened for frc and oxc genes. With the exception of Lactobacillus gasseri and Bifidobacterium lactis, none of the other strains harbored genes for oxalate utilization.

Characterization of a Novel Bile-Inducible Operon Encoding a Two-Component Regulatory System inLactobacillus acidophilus

“…A cluster of genes seemingly unrelated by function (LBA1425 to LBA1432) was significantly induced in the presence of bile, as indicated by the microarray experiments (ranging from 2.1-to 3.0-fold upregulation). To date, this group of genes has not been shown to be differentially expressed under any test conditions examined (2,3,6). This cluster was particularly interesting because it contained genes for a type IIIA HPK (LBA1430) and an RR of the OmpR family (LBA1431), both with uncharacterized functions (1).…”

A Randomized, Controlled Trial of Lactic Acid Bacteria for Idiopathic Hyperoxaluria

“…Another strain of L. acidophilus has the frc and oxc genes. It is interesting that their transcription occurred only when first adapted to subinhibitory concentrations of oxalate and then exposed to pH 5.5 (11). These requirements for gene transcrip- tion may explain the failure to detect previously the genes in Oxadrop strains (3).…”

Cholesterol removal by Lactobacillus plantarum isolated from homemade fermented cream in Inner Mongolia of China

“…Th e time from entering the stomach to release is estimated to be approximately 90 min, with the following digestive processes requiring a longer residence time (Berrada et al 1991). The microorganisms stresses begin in the stomach with its internal pH ranging between 1 and 3 (Azcarate- Peril et al 2006). As shown above, a condition such as pH 2.5 for 2 h was selected to examine the acid tolerance of the tested strains.…”