Oxalate-Degrading Activity in Bifidobacterium animalis subsp. lactis : Impact of Acidic Conditions on the Transcriptional Levels of the Oxalyl Coenzyme A (CoA) Decarboxylase and Formyl-CoA Transferase Genes

Abstract

Oxalic acid occurs extensively in nature and plays diverse roles, especially in pathological processes. Due to its highly oxidizing effects, hyperabsorption or abnormal synthesis of oxalate can cause serious acute disorders in mammals and can be lethal in extreme cases. Intestinal oxalate-degrading bacteria could therefore be pivotal in maintaining oxalate homeostasis and reducing the risk of kidney stone development. In this study, the oxalate-degrading activities of 14 bifidobacterial strains were measured by a capillary electrophoresis technique. The oxc gene, encoding oxalyl-coenzyme A (CoA) decarboxylase, a key enzyme in oxalate catabolism, was isolated by probing a genomic library of Bifidobacterium animalis subsp. lactis BI07, which was one of the most active strains in the preliminary screening. The genetic and transcriptional organization of oxc flanking regions was determined, unraveling the presence of two other independently transcribed open reading frames, potentially responsible for the ability of B. animalis subsp. lactis to degrade oxalate. pH-controlled batch fermentations revealed that acidic conditions were a prerequisite for a significant oxalate degradation rate, which dramatically increased in cells first adapted to subinhibitory concentrations of oxalate and then exposed to pH 4.5. Oxalate-preadapted cells also showed a strong induction of the genes potentially involved in oxalate catabolism, as demonstrated by a transcriptional analysis using quantitative real-time reverse transcription-PCR. These findings provide new insights into the characterization of oxalate-degrading probiotic bacteria and may support the use of B. animalis subsp. lactis as a promising adjunct for the prophylaxis and management of oxalate-related kidney disease.Oxalate is a normal end product of amino acid metabolism and must be excreted, predominantly via the kidney, to maintain homeostasis (22). Oxalate is also present in a wide range of foods and drinks, and the normal dietary intake is variable, ranging from 70 to 920 mg per day (23). Because of its highly oxidizing effects and the capability to combine with cations to form insoluble salts, this organic dicarboxylate is extremely toxic for most forms of life. In humans, oxalate can cause a variety of pathological disorders, including hyperoxaluria, urolithiasis, cardiomyopathy, and renal failure (29,41,59). Hyperoxaluria is the single strongest promoter of kidney stone formation, whose medical management represents a burden to the individual patient as well as the health care system (49). The lack of new medications and the continued poor compliance with drug therapy have led to a growing interest in dietary manipulation and novel therapies aimed at preventing recurrent stone formation. Unfortunately, an oxalate-free diet is difficult to achieve and would probably be deficient in essential nutrients. Hence, other approaches to reducing urinary oxalate for management of stone disease have been explored.The discovery of oxalate-degrading bacteria within the human ...

YfdW and YfdU Are Required for Oxalate-Induced Acid Tolerance in Escherichia coli K-12

“…This activation effect was reported previously for oxalate metabolism in Bifidobacterium: preadaptation with subinhibitory concentrations of oxalate and lower pH resulted in increased oxc and frc mRNA concentrations (56). Stationary-phase cells (pH 5.5) exhibited a 4-fold increase in survival after incubation with 50 mM oxalate for 6 min.…”

“…The yfdXWUVE operon in E. coli responds to the EvgAS regulatory system, and deletion of the operon results in reduced survival of wild-type K-12 MG1655 cells at pH 2.5 when EvgA is overexpressed in the cells (12), but these proteins are not linked to multidrug resistance in E. coli (55). Turroni et al previously reported a link to increased expression of oxc and frc mRNAs in bifidobacteria when cells are preadapted in oxalate and subsequently exposed to lower pH and higher oxalate concentrations (56). Previous microarray experiments have shown that yhjX, a putative oxalate:formate antiporter, is upregulated when cells undergo cytoplasmic acidification by treatment with benzoate (57).…”

The Gastrointestinal Tract of the White-Throated Woodrat (Neotoma albigula) Harbors Distinct Consortia of Oxalate-Degrading Bacteria

“…Thus, the pH of each gut region may be another important factor driving in vivo oxalate degradation and the densities of different species of oxalate-degrading bacteria. The genera Bifidobacterium and Lactobacillus degrade oxalate optimally at pH 4.5 and 5.5, respectively (35,44). However, optimal pH for oxalate-degrading activity within the Oxalobacter genus was reported as 6.4, after examination over the range of pH 5 to 8 (55).…”

“…One of the best-studied species is Oxalobacter formigenes, which requires oxalate as a carbon and energy source for growth (8). However, other oxalate-degrading bacteria include species from the genera Lactobacillus, Bifidobacterium, Streptococcus, Enterococcus, and others (11,(32)(33)(34)(35). The majority of studies investigating oxalate-degrading bacteria have been conducted on humans, lab rats, and agricultural systems.…”

Effect of Dietary Oxalate on the Gut Microbiota of the Mammalian Herbivore Neotoma albigula

“…Previous research has focused on the role of individual taxa in oxalate degradation (7,20,29,37,38). However, several oxalate-degrading taxa have now been identified from the mammalian gut, and other taxa may be affected by oxalate in obscure ways (20,26,39,40). To address the gaps, we combined controlled laboratory diet trials, physiological assays, and microbial ecology to examine the taxonomic and functional response of the whole gut microbiota in a mammalian herbivore, N. albigula, which naturally consumes large amounts of oxalate in its diet, a simple compound that is metabolized exclusively by the gut microbiota (18,26).…”