Oxalate-degrading Enterococcus faecalis

Bacterial Degradation of Antinutrients in Foods: The Genomic Insight

Antinutrients, also known as anti-nutritional factors (ANFs), are compounds found in many plant-based foods that can limit the bioavailability of nutrients or can act as precursors to toxic substances. ANFs have controversial effects on human health, depending mainly on their concentration. While the positive effects of these compounds are well documented, the dangers they pose and the approaches to avoid them have not been discussed to the same extent. There is no dispute that many ANFs negatively alter the absorption of vitamins, minerals, and proteins in addition to inhibiting some enzyme activities, thus negatively affecting the bioavailability of nutrients in the human body. This review discusses the chemical properties, plant bioavailability, and deleterious effects of anti-minerals (phytates and oxalates), glycosides (cyanogenic glycosides and saponins), polyphenols (tannins), and proteinaceous ANFs (enzyme inhibitors and lectins). The focus of this study is on the possibility of controlling the amount of ANF in food through fermentation. An overview of the most common biochemical pathways for their microbial reduction is provided, showing the genetic basis of these phenomena, including the active enzymes, the optimal conditions of action, and some data on the regulation of their synthesis.

Dietary Exposure to Acrylamide Has Negative Effects on the Gastrointestinal Tract: A Review

Changing eating habits and an increase in consumption of thermally processed products have increased the risk of the harmful impact of chemical substances in food on consumer health. A 2002 report by the Swedish National Food Administration and scientists at Stockholm University on the formation of acrylamide in food products during frying, baking and grilling contributed to an increase in scientific interest in the subject. Acrylamide is a product of Maillard's reaction, which is a non-enzymatic chemical reaction between reducing sugars and amino acids that takes place during thermal processing. The research conducted over the past 20 years has shown that consumption of acrylamide-containing products leads to disorders in human and animal organisms. The gastrointestinal tract is a complex regulatory system that determines the transport, grinding, and mixing of food, secretion of digestive juices, blood flow, growth and differentiation of tissues, and their protection. As the main route of acrylamide absorption from food, it is directly exposed to the harmful effects of acrylamide and its metabolite-glycidamide. Despite numerous studies on the effect of acrylamide on the digestive tract, no comprehensive analysis of the impact of this compound on the morphology, innervation, and secretory functions of the digestive system has been made so far. Acrylamide present in food products modifies the intestine morphology and the activity of intestinal enzymes, disrupts enteric nervous system function, affects the gut microbiome, and increases apoptosis, leading to gastrointestinal tract dysfunction. It has also been demonstrated that it interacts with other substances in food in the intestines, which increases its toxicity. This paper summarises the current knowledge of the impact of acrylamide on the gastrointestinal tract, including the enteric nervous system, and refers to strategies aimed at reducing its toxic effect.

Co-ensiled rice straw with whole sugar beet and its effect on the performance of lactating cows

This study investigated the effect of co-ensiled rice straw (RS) with whole sugar beet (SB) on lactating cows' performance. Ensiled rice straw (ERS) as control (CGS) was incorporated with immersed corn grains (CG) for 24 h, while the 2nd and 3rd ensiled RS (LSB and HSB) contained SB substituted of 50 and 100% of CG on an energy basis (total digestible nutrients, TDN), respectively. In the experimental diets, D1, D2, and D3, which include CGS, LSB, and HSB provided ad-libitum, respectively, while a concentrated feed mixture (2% of body weight) was offered. The population of lactic acid bacteria was slightly higher with fed HSB, relative to LSB and CGS. The OM, CP, EE, NFC, and TCH contents of CGS were slightly higher than LSB and HSB, while the opposite happened with the aNDFom, and ADFom contents. The digestibility of DM, OM, aNDFom, and ADFom of the D3 group was higher (P < 0.05) than in D1 and D2. The D3 recorded the highest values (P < 0.05) of silage consumption, and palatability. Milk production, fat-corrected milk (FCM), and energy-corrected milk (ECM) were (P < 0.05) higher for cows fed D3 compared with D1 and D2. Fat, protein, lactose, and total solids were trending on the same track. The feed conversion ratio (FCR) of cows fed diet D3 was better than cows fed D1 diet. The level of glucose in the blood increased (P < 0.05) significantly with feeding on HSB than LSB, which was significantly (P < 0.05) higher compared to CGS. In conclusion, co-ensiling of RS with the whole SB plant consider a good method to improve its nutritional value.

Expression Optimizing of Recombinant Oxalyl-CoA Decarboxylase in Escherichia coli

Background

One of the most common diseases of the urinary tract is stones of this system, including kidney stones. About 70%-80% of kidney stones are calcium oxalate. Oxalyl-CoA decarboxylase is a single polypeptide included of 568 amino acids which play a key role in oxalate degradation.

Materials and Methods

The aim of current study is high-level expression of oxalyl-CoA decarboxylase in Escherichia coli BL21 (DE3). To achieve this aim, oxalyl-CoA decarboxylase gene was cloned upon pET-30a (+) with T7 promoter. The vector containing the oxalyl-CoA decarboxylase gene was transformed into E. coli and the expression of the gene was examined on a laboratory scale and fermentor. Atfirst, the effect of temperature, culture medium, and induction time on oxalyl-CoA decarboxylase expression at three levels was examined.

Results

The obtained data showed that the highest expression was related to the terrific broth culture medium and temperature of 32°C with an inducer concentration of 1 mM. Under this situation the ultimate cells dry weight and the final oxalyl-CoA decarboxylase expression were 2.46 g/l and 36% of total protein, respectively. Then induction time was optimized in a bench bioreactor and productivity of oxalyl-CoA decarboxylase was calculated. Under optimized condition the cell density, biomass productivity and oxalyl-CoA decarboxylase concentration reached 4.02 g/l, 0.22 g/l/h, and 0.7 g/l which are one of the highest reported rates.

Conclusion

This study demonstrated that high levels of oxalyl-CoA decarboxylase can be achieved by optimizing the expression conditions.

Understanding interactions among diet, host and gut microbiota for personalized nutrition

Human responses to the same diets may vary to a large extent, depending on the complex diet-host-microbiota interactions. Recent scientific advance has indicated that this diet-host-microbiota interaction could be quantified to develop strategies for improving individual health (personalized nutrition). Compared to the host related factors (which are difficult to manipulate), the gut microbiome is more readily modulated by dietary exposures and has important roles in affecting human health via the synthesis of various bioactive compounds and participating in the digestion and absorption process of macro- and micronutrients. Therefore, gut microbiota alterations induced by diets could possibly be utilized to improve human health in a targeted manner. However, limitations in the processing and analysis of 'big-data' concerning human microbiome still restrict the translational capacity of diet-host-microbiota interactions into tools to improve personalized human health. In the current review, recent advances in terms of understanding the specific diet-host-microbiota interactions were summarized, aiming to help the development of strategies for personalized nutrition.

The Complex Role of Lactic Acid Bacteria in Food Detoxification

Toxic ingredients in food can lead to serious food-related diseases. Such compounds are bacterial toxins (Shiga-toxin, listeriolysin, Botulinum toxin), mycotoxins (aflatoxin, ochratoxin, zearalenone, fumonisin), pesticides of different classes (organochlorine, organophosphate, synthetic pyrethroids), heavy metals, and natural antinutrients such as phytates, oxalates, and cyanide-generating glycosides. The generally regarded safe (GRAS) status and long history of lactic acid bacteria (LAB) as essential ingredients of fermented foods and probiotics make them a major biological tool against a great variety of food-related toxins. This state-of-the-art review aims to summarize and discuss the data revealing the involvement of LAB in the detoxification of foods from hazardous agents of microbial and chemical nature. It is focused on the specific properties that allow LAB to counteract toxins and destroy them, as well as on the mechanisms of microbial antagonism toward toxigenic producers. Toxins of microbial origin are either adsorbed or degraded, toxic chemicals are hydrolyzed and then used as a carbon source, while heavy metals are bound and accumulated. Based on these comprehensive data, the prospects for developing new combinations of probiotic starters for food detoxification are considered.

Probiotics in the Prevention of the Calcium Oxalate Urolithiasis

Nephrolithiasis ranks third among urological diseases in terms of prevalence, making up about 15% of cases. The continued increase in the incidence of nephrolithiasis is most probably due to changes in eating habits (high protein, sodium, and sugar diets) and lifestyle (reduced physical activity) in all developed countries. Some 80% of all kidney stones cases are oxalate urolithiasis, which is also characterized by the highest risk of recurrence. Frequent relapses of nephrolithiasis contribute to severe complications and high treatment costs. Unfortunately, there is no known effective way to prevent urolithiasis at present. In cases of diet-related urolithiasis, dietary changes may prevent recurrence. However, in some patients, the condition is unrelated to diet; in such cases, there is evidence to support the use of stone-related medications. Interestingly, a growing body of evidence indicates the potential of the microbiome to reduce the risk of developing renal colic. Previous studies have primarily focused on the use of Oxalobacterformigenes in patients with urolithiasis. Unfortunately, this bacterium is not an ideal probiotic due to its antibiotic sensitivity and low pH. Therefore, subsequent studies sought to find bacteria which are capable of oxalate degradation, focusing on well-known probiotics including Lactobacillus and Bifidobacterium strains, Eubacterium lentum, Enterococcus faecalis, and Escherichia coli.

The controversial association of gut and urinary microbiota with kidney stone formation

Nephrolithiasis (kidney stones) is one of the most common chronic kidney diseases that are typically more common among adult men comparing to adult women. The prevalence of this disease is increasing which is influenced by genetic and environmental factors. Kidney stones are mainly composed of calcium oxalate and urinary oxalate which is considered a dangerous factor in their formation. Besides diverse leading reasons in the progression of nephrolithiasis, the gut and urinary microbiome has been recognized as a major player in the development or prevention of it. These microbes produce metabolites that have diverse effects on host biological functions. Therefore, Changes in the composition and structure of the microbiome (dysbiosis) have been implicated in various diseases. The present review focuses on the roles of gut and urinary in kidney stone formation.

Microbial Profile of the Ventriculum of Honey Bee (Apis mellifera ligustica Spinola, 1806) Fed with Veterinary Drugs, Dietary Supplements and Non-Protein Amino Acids

The effects of veterinary drugs, dietary supplements and non-protein amino acids on the European honey bee (Apis mellifera ligustica Spinola, 1806) ventriculum microbial profile were investigated. Total viable aerobic bacteria, Enterobacteriaceae, staphylococci, Escherichia coli, lactic acid bacteria, Pseudomonas spp., aerobic bacterial endospores and Enterococcus spp. were determined using a culture-based method. Two veterinary drugs (Varromed® and Api-Bioxal®), two commercial dietary supplements (ApiHerb® and ApiGo®) and two non-protein amino acids (GABA and beta-alanine) were administered for one week to honey bee foragers reared in laboratory cages. After one week, E. coli and Staphylococcus spp. were significantly affected by the veterinary drugs (p < 0.001). Furthermore, dietary supplements and non-protein amino acids induced significant changes in Staphylococcus spp., E. coli and Pseudomonas spp. (p < 0.001). In conclusion, the results of this investigation showed that the administration of the veterinary drugs, dietary supplements and non-protein amino acids tested, affected the ventriculum microbiological profile of Apis mellifera ligustica.GABA; beta-alanine; oxalic acid; diet effect; microbiota.

Oxalate-degrading bacteria, including Oxalobacter formigenes, colonise the gastrointestinal tract of healthy koalas (Phascolarctos cinereus) and those with oxalate nephrosis

BACKGROUND

Koalas in the Mount Lofty Ranges, South Australia, have a high prevalence of oxalate nephrosis, or calcium oxalate kidney crystals. Gastrointestinal tract oxalate-degrading bacteria, particularly Oxalobacter formigenes, have been identified in other animal species and humans, and their absence or low abundance is postulated to increase the risk of renal oxalate diseases. This study aimed to identify oxalate-degrading bacteria in the gastrointestinal tract of koalas and determine their association with oxalate nephrosis.

METHODS

Caecal and faecal samples were collected at necropsy from 22 Mount Lofty Ranges koalas that had been euthanased on welfare grounds, with 8 koalas found to have oxalate nephrosis by renal histopathology. Samples were analysed by PCR for the oxc gene, which encodes oxalyl-CoA decarboxylase, and also by Illumina sequencing of the V3-V4 region of the bacterial 16S rRNA gene.

RESULTS

The oxc gene was detected in 100% of koala samples, regardless of oxalate nephrosis status. Oxalobacter formigenes was detected in all but one faecal sample, with no difference in abundance between koalas affected and unaffected by oxalate nephrosis. Other species of known oxalate-degrading bacteria were infrequently detected.

CONCLUSION

This is the first study to identify Oxalobacter and other oxalate-degrading bacterial species in koalas, but an association with oxalate nephrosis and absence or low abundance of Oxalobacter was not found. This suggests other mechanisms underlie the risk of oxalate nephrosis in koalas.

Inhibition of urinary stone disease by a multi-species bacterial network ensures healthy oxalate homeostasis

The incidence of urinary stone disease is rapidly increasing, with oxalate being a primary constituent of approximately 80% of all kidney stones. Despite the high dietary exposure to oxalate by many individuals and its potential nephrotoxicity, mammals do not produce enzymes to metabolize this compound, instead relying in part on bacteria within the gut to reduce oxalate absorption and urinary excretion. While considerable research has focused on isolated species of oxalate-degrading bacteria, particularly those with an absolute requirement for oxalate, recent studies have pointed to broader roles for microbiota both in oxalate metabolism and inhibition of urinary stone disease. Here we examined gut microbiota from patients with and live-in individuals without urinary stone disease to determine if healthy individuals harbored a more extensive microbial network associated with oxalate metabolism. We found a gender-specific association between the gut microbiota composition and urinary stone disease. Bacteria enriched in healthy individuals largely overlapped with those that exhibited a significant, positive correlation with Oxalobacter formigenes, a species presumed to be at the center of an oxalate-metabolizing microbial network. Furthermore, differential abundance analyses identified multiple taxa known to also be stimulated by oxalate in rodent models. Interestingly, the presence of these taxa distinguished patients from healthy individuals better than either the relative abundance or colonization of O. formigenes. Thus, our work shows that bacteria stimulated by the presence of oxalate in rodents may, in addition to obligate oxalate users, play a role in the inhibition of urinary stone disease in man.

Drug-Induced Kidney Stones and Crystalline Nephropathy: Pathophysiology, Prevention and Treatment

Drug-induced calculi represent 1-2% of all renal calculi. The drugs reported to produce calculi may be divided into two groups. The first one includes poorly soluble drugs with high urine excretion that favour crystallisation in the urine. Among them, drugs used for the treatment of patients with human immunodeficiency, namely atazanavir and other protease inhibitors, and sulphadiazine used for the treatment of cerebral toxoplasmosis, are the most frequent causes. Besides these drugs, about 20 other molecules may induce nephrolithiasis, such as ceftriaxone or ephedrine-containing preparations in subjects receiving high doses or long-term treatment. Calculi analysis by physical methods including infrared spectroscopy or X-ray diffraction is needed to demonstrate the presence of the drug or its metabolites within the calculi. Some drugs may also provoke heavy intra-tubular crystal precipitation causing acute renal failure. Here, the identification of crystalluria or crystals within the kidney tissue in the case of renal biopsy is of major diagnostic value. The second group includes drugs that provoke the formation of urinary calculi as a consequence of their metabolic effects on urinary pH and/or the excretion of calcium, phosphate, oxalate, citrate, uric acid or other purines. Among such metabolically induced calculi are those formed in patients taking uncontrolled calcium/vitamin D supplements, or being treated with carbonic anhydrase inhibitors such as acetazolamide or topiramate. Here, diagnosis relies on a careful clinical inquiry to differentiate between common calculi and metabolically induced calculi, of which the incidence is probably underestimated. Specific patient-dependent risk factors also exist in relation to urine pH, volume of diuresis and other factors, thus providing a basis for preventive or curative measures against stone formation.

Microbiota Diversification and Crash Induced by Dietary Oxalate in the Mammalian Herbivore Neotoma albigula

The bacteria associated with mammalian hosts exhibit extensive interactions with overall host physiology and contribute significantly to the health of the host. Bacteria are vital to the mitigation of the toxic effects of oxalate specifically as mammals do not possess the enzymes to degrade this compound, which is present in the majority of kidney stones. Contrary to the body of literature on a few oxalate-degrading specialists, our work illustrates that oxalate stimulates a broad but cohesive microbial network in a dose-dependent manner. The unique characteristics of the N. albigula microbiota make it an excellent source for the development of bacteriotherapies to inhibit kidney stone formation. Furthermore, this work successfully demonstrates methods to identify microbial networks responsive to specific toxins, their limits, and important elements such as microbial network cohesivity and architecture. These are necessary steps in the development of targeted bacteriotherapies.

Oxalate, broadly found in both dietary and endogenous sources, is a primary constituent in 80% of kidney stones, an affliction that has tripled in prevalence over the last 40 years. Oxalate-degrading bacteria within the gut microbiota can mitigate the effects of oxalate and are negatively correlated with kidney stone formation, but bacteriotherapies involving oxalate-degrading bacteria have met with mixed results. To inform the development of more effective and consistent bacteriotherapies, we sought to quantify the interactions and limits between oxalate and an oxalate-adapted microbiota from the wild mammalian herbivore Neotoma albigula (woodrat), which consumes a high-oxalate diet in the wild. We tracked the microbiota over a variable-oxalate diet ranging from 0.2% to 12%, with the upper limit approximating 10× the level of human consumption. The N. albigula microbiota was capable of degrading ~100% of dietary oxalate regardless of the amount consumed. However, the microbiota exhibited significant changes in diversity dynamically at the operational taxonomic unit (OTU), family, and community levels in accordance with oxalate input. Furthermore, a cohesive microbial network was stimulated by the consumption of oxalate and exhibited some resistance to the effects of prolonged exposure. This study demonstrates that the oxalate-adapted microbiota of N. albigula exhibits a very high level of degradation and tolerance for oxalate.

IMPORTANCE The bacteria associated with mammalian hosts exhibit extensive interactions with overall host physiology and contribute significantly to the health of the host. Bacteria are vital to the mitigation of the toxic effects of oxalate specifically as mammals do not possess the enzymes to degrade this compound, which is present in the majority of kidney stones. Contrary to the body of literature on a few oxalate-degrading specialists, our work illustrates that oxalate stimulates a broad but cohesive microbial network in a dose-dependent manner. The unique characteristics of the N. albigula microbiota make it an excellent source for the development of bacteriotherapies to inhibit kidney stone formation. Furthermore, this work successfully demonstrates methods to identify microbial networks responsive to specific toxins, their limits, and important elements such as microbial network cohesivity and architecture. These are necessary steps in the development of targeted bacteriotherapies.

The Induction of Oxalate Metabolism In Vivo Is More Effective with Functional Microbial Communities than with Functional Microbial Species

For mammals, oxalate enters the body through the diet or is endogenously produced by the liver; it is removed by microbial oxalate metabolism in the gut and/or excretion in feces or urine. Deficiencies in any one of the these pathways can lead to complications, such as calcium oxalate urinary stones. While considerable research has been conducted on individual oxalate-degrading bacterial isolates, interactions between oxalate and the gut microbiota as a whole are unknown. We examined the reduction in oxalate excretion in a rat model following oral administration of fecal microbes from a mammalian herbivore adapted to a high oxalate diet or to fecal transplants consisting of two different formulations of mixed oxalate-degrading isolates. While all transplants elicited a significant reduction in oxalate excretion initially, the greatest effect was seen with fecal microbial transplants, which persisted even in the absence of dietary oxalate. The reduction in oxalate excretion in animals given fecal transplants corresponded with the establishment of diverse bacteria, including known oxalate-degrading bacteria and a cohesive network of bacteria centered on oxalate-degrading specialists from the Oxalobacteraceae family. Results suggested that the administration of a complete community of bacteria facilitates a cohesive balance in terms of microbial interactions. Our work offers important insights into the development of targeted bacteriotherapies intended to reduce urinary oxalate excretion in patients at risk for recurrent calcium oxalate stones as well as bacteriotherapies targeting other toxins for elimination. IMPORTANCE Oxalate is a central component in 80% of kidney stones. While mammals do not possess the enzymes to degrade oxalate, many gastrointestinal bacteria are efficient oxalate degraders. We examined the role of cohesive microbial networks for oxalate metabolism, using Sprague-Dawley rats as a model host. While the transplantation of oxalate-degrading bacteria alone to the Sprague-Dawley hosts did increase oxalate metabolism, fecal transplants from a wild mammalian herbivore, Neotoma albigula, had a significantly greater effect. Furthermore, the boost for oxalate metabolism persisted only in animals that received fecal transplants. Animals receiving fecal transplants had a more diverse and cohesive network of bacteria associated with the Oxalobacteraceae, a family known to consist of specialist oxalate-degrading bacteria, than did animals that received oxalate-degrading bacteria alone. Our results indicate that fecal transplants are more effective at transferring specific functions than are microbial specialists alone, which has broad implications for the development of bacteriotherapies.

Putative mechanisms of kiwifruit on maintenance of normal gastrointestinal function

Kiwifruits are recognized as providing relief from constipation and symptoms of constipation-predominant irritable bowel syndrome (IBS-C). However, the underlying mechanisms, specifically in regards to gastrointestinal transit time and motility, are still not completely understood. This review provides an overview on the physiological and pathophysiological processes underlying constipation and IBS-C, the composition of kiwifruit, and recent advances in the research of kiwifruit and abdominal comfort. In addition, gaps in the research are highlighted and scientific studies of other foods with known effects on the gastrointestinal tract are consulted to find likely mechanisms of action. While the effects of kiwifruit fiber are well documented, observed increases in gastrointestinal motility caused by kiwifruit are not fully characterized. There are a number of identified mechanisms that may be activated by kiwifruit compounds, such as the induction of motility via protease-activated signaling, modulation of microflora, changes in colonic methane status, bile flux, or mediation of inflammatory processes.

Modeling time-series data from microbial communities

As sequencing technologies have advanced, the amount of information regarding the composition of bacterial communities from various environments (for example, skin or soil) has grown exponentially. To date, most work has focused on cataloging taxa present in samples and determining whether the distribution of taxa shifts with exogenous covariates. However, important questions regarding how taxa interact with each other and their environment remain open thus preventing in-depth ecological understanding of microbiomes. Time-series data from 16S rDNA amplicon sequencing are becoming more common within microbial ecology, but methods to infer ecological interactions from these longitudinal data are limited. We address this gap by presenting a method of analysis using Poisson regression fit with an elastic-net penalty that (1) takes advantage of the fact that the data are time series; (2) constrains estimates to allow for the possibility of many more interactions than data; and (3) is scalable enough to handle data consisting of thousands of taxa. We test the method on gut microbiome data from white-throated woodrats (Neotoma albigula) that were fed varying amounts of the plant secondary compound oxalate over a period of 22 days to estimate interactions between OTUs and their environment.

Screening of Oxalate Degrading Lactic Acid Bacteria of Food Origin

A screening for oxalate degrading abilities was initially carried on within Lactic Acid Bacteria cultures of different food origin. Seventy-nine strains were drop-inoculated onto MRS agar plates containing calcium oxalate. By comparing colonies diameters, 31 strains were used to inoculate, in parallel, MRS and MRS modified by sodium oxalate addition. Differences in the strains’ growth were assessed by colony forming unit counts. For two strains, the growth in oxalate enriched medium was significantly higher; while, for eleven strains an opposite behaviour was recorded. Two strains – probiotic Lactobacillus rhamnosus LbGG and Enterococcus faecalis 59 – were chosen. The first strain appeared to be able to metabolize oxalate more efficiently than the other tested cultures, while strain 59 appeared unable to gather advantage by oxalates and, indeed, appeared to be inhibited by the salt presence in the medium. Outcomes revealed that higher glucose concentrations may favour oxalates utilization. In MRS with oxalate, but without glucose, citrate was completely metabolized. Evaluation along time confirmed that the oxalate degradation is more significant in presence of glucose. Outcomes may represent a good start for the development of a safe and even probiotic culture able to lower the oxalates content of food.

Microbial Community Transplant Results in Increased and Long-Term Oxalate Degradation

Gut microbes are essential for the degradation of dietary oxalate, and this function may play a role in decreasing the incidence of kidney stones. However, many oxalate-degrading bacteria are susceptible to antibiotics and the use of oxalate-degrading probiotics has only led to an ephemeral reduction in urinary oxalate. The objective of the current study was to determine the efficacy of using whole-community microbial transplants from a wild mammalian herbivore, Neotoma albigula, to increase oxalate degradation over the long term in the laboratory rat, Rattus norvegicus. We quantified the change in total oxalate degradation in lab rats immediately after microbial transplants and at 2- and 9-month intervals following microbial transplants. Additionally, we tracked the fecal microbiota of the lab rats, with and without microbial transplants, using high-throughput Illumina sequencing of a hyper-variable region of the 16S rRNA gene. Microbial transplants resulted in a significant increase in oxalate degradation, an effect that persisted 9 months after the initial transplants. Functional persistence was corroborated by the transfer, and persistence of a group of bacteria previously correlated with oxalate consumption in N. albigula, including an anaerobic bacterium from the genus Oxalobacter known for its ability to use oxalate as a sole carbon source. The results of this study indicate that whole-community microbial transplants are an effective means for the persistent colonization of oxalate-degrading bacteria in the mammalian gut.

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

Diet is one of the primary drivers that sculpts the form and function of the mammalian gut microbiota. However, the enormous taxonomic and metabolic diversity held within the gut microbiota makes it difficult to isolate specific diet-microbe interactions. The objective of the current study was to elucidate interactions between the gut microbiota of the mammalian herbivore Neotoma albigula and dietary oxalate, a plant secondary compound (PSC) degraded exclusively by the gut microbiota. We quantified oxalate degradation in N. albigula fed increasing amounts of oxalate over time and tracked the response of the fecal microbiota using high-throughput sequencing. The amount of oxalate degraded in vivo was linearly correlated with the amount of oxalate consumed. The addition of dietary oxalate was found to impact microbial species diversity by increasing the representation of certain taxa, some of which are known to be capable of degrading oxalate (e.g., Oxalobacter spp.). Furthermore, the relative abundances of 117 operational taxonomic units (OTU) exhibited a significant correlation with oxalate consumption. The results of this study indicate that dietary oxalate induces complex interactions within the gut microbiota that include an increase in the relative abundance of a community of bacteria that may contribute either directly or indirectly to oxalate degradation in mammalian herbivores.

A review of the interactions between acrylamide, microorganisms and food components

Acrylamide (AA) and its metabolites have been recognized as potential carcinogens, but also they can cause other negative symptoms in human or animal organisms and therefore this class of chemical compounds has attracted a lot of attention.

Secondary hyperoxaluria: a risk factor for kidney stone formation and renal failure in native kidneys and renal grafts

Secondary hyperoxaluria is a multifactorial disease affecting several organs and tissues, among which stand native and transplanted kidneys. Nephrocalcinosis and nephrolithiasis may lead to renal insufficiency. Patients suffering from secondary hyperoxaluria, should be promptly identified and appropriately treated, so that less renal damage occurs. The aim of this review is to underline the causes of hyperoxaluria and the related pathophysiologic mechanisms, which are involved, along with the description of seven cases of irreversible renal graft injury due to secondary hyperoxaluria.

The gastrointestinal tract of the white-throated Woodrat (Neotoma albigula) harbors distinct consortia of oxalate-degrading bacteria

The microbiota inhabiting the mammalian gut is a functional organ that provides a number of services for the host. One factor that may regulate the composition and function of gut microbial communities is dietary toxins. Oxalate is a toxic plant secondary compound (PSC) produced in all major taxa of vascular plants and is consumed by a variety of animals. The mammalian herbivore Neotoma albigula is capable of consuming and degrading large quantities of dietary oxalate. We isolated and characterized oxalate-degrading bacteria from the gut contents of wild-caught animals and used high-throughput sequencing to determine the distribution of potential oxalate-degrading taxa along the gastrointestinal tract. Isolates spanned three genera: Lactobacillus, Clostridium, and Enterococcus. Over half of the isolates exhibited significant oxalate degradation in vitro, and all Lactobacillus isolates contained the oxc gene, one of the genes responsible for oxalate degradation. Although diverse potential oxalate-degrading genera were distributed throughout the gastrointestinal tract, they were most concentrated in the foregut, where dietary oxalate first enters the gastrointestinal tract. We hypothesize that unique environmental conditions present in each gut region provide diverse niches that select for particular functional taxa and communities.

The metabolic and ecological interactions of oxalate-degrading bacteria in the Mammalian gut

Oxalate-degrading bacteria comprise a functional group of microorganisms, commonly found in the gastrointestinal tract of mammals. Oxalate is a plant secondary compound (PSC) widely produced by all major taxa of plants and as a terminal metabolite by the mammalian liver. As a toxin, oxalate can have a significant impact on the health of mammals, including humans. Mammals do not have the enzymes required to metabolize oxalate and rely on their gut microbiota for this function. Thus, significant metabolic interactions between the mammalian host and a complex gut microbiota maintain the balance of oxalate in the body. Over a dozen species of gut bacteria are now known to degrade oxalate. This review focuses on the host-microbe and microbe-microbe interactions that regulate the degradation of oxalate by the gut microbiota. We discuss the pathways of oxalate throughout the body and the mammalian gut as a series of differentiated ecosystems that facilitate oxalate degradation. We also explore the mechanisms and functions of microbial oxalate degradation along with the implications for the ecological and evolutionary interactions within the microbiota and for mammalian hosts. Throughout, we consider questions that remain, as well as recent technological advances that can be employed to answer them.

Oxalate-degrading capacities of lactic acid bacteria in canine feces

In this study, lactic acid bacteria in canine feces were isolated and identified, and their oxalate-degrading capacities were evaluated. The oxalate-degrading capacities were determined for 24 of 47 (51.06%) lactic acid bacteria isolates. Of these, 8 isolates [Leuconostoc mesenteroides (RL75), Lactococcus garvieae (CD2), Lactococcus subsp. lactis (CS21), Enterococcus faecium (CL71 and CL72), and Enterococcus faecalis (CD14, CS62, and CD12)] degraded more than 5% of the oxalate present, while the others degraded less than 5% of the oxalate in vitro. Isolates that degraded more than 5% of the oxalate present were selected for further examination. The oxalate-degrading capacities of individual isolates, a mixture of Enterococcus, a mixture of Lactococcus, and a mixture of the eight isolates were evaluated in media containing different concentrations of glucose (sufficient, insufficient, or no glucose). In comparison with the control medium, all of the individual isolates and mixtures of isolates could degrade oxalate in all three groups (P<0.05). In most cases, the isolates growing in medium with 20 g/L of glucose had higher oxalate-degrading capacities than those growing in medium with 2.5 g/L of glucose or no glucose. The mixture of all isolates showed higher oxalate-degrading capacity than the individual isolates and other mixtures. The oxalate-degrading capacities of the isolates were isolate dependent.

Probiotic-induced reduction of gastrointestinal oxalate absorption in healthy subjects

Both a high dietary oxalate intake and increased intestinal absorption appear to be major causes of elevated urine oxalate, a risk factor for kidney stone formation. By favorably altering the gastrointestinal bacterial population, probiotics have the potential to lower oxalate absorption/urinary excretion. This study assessed whether a 4-wk daily consumption of a commercially available probiotic by 11 healthy volunteers (8 females, 3 males), aged 21-36 y, would decrease oxalate absorption. The study involved the ingestion of a probiotic (VSL#3) for a 4 wk period followed by a 4 wk washout period. Oxalate load tests, providing a total of 80 mg oxalate, were conducted at baseline (pre-probiotic), and after the probiotic and washout periods. In the total subject population, mean total 22 h oxalate absorption at baseline (30.8 %) was significantly higher than after the probiotic (11.6 %) and washout (11.5 %) periods. However, four subjects identified as high oxalate absorbers at baseline had a particularly marked probiotic-induced reduction in oxalate absorption, which largely accounted for the reduction observed in the total subject population. The overall data suggested that in individuals characterized by high oxalate absorption levels, VSL#3 ingestion has the potential to reduce gastrointestinal oxalate absorption, which could decrease risk of kidney stones and other disorders related to hyperoxaluria.

Clinical evaluation of urolithiasis in Crohn's disease

OBJECTIVES

To investigate the characteristics of urolithiasis associated with Crohn's disease in a Japanese population.

METHODS

We studied 98 patients with Crohn's disease: 39 with urolithiasis and 59 without urolithiasis. Patients were treated at the Social Insurance Central General Hospital, or at the Toho University Omori, Ohashi, or Sakura Medical Centers.

RESULTS

Calculi were more frequent in men (n = 30) than women (n = 9). Mean time from diagnosis of Crohn's disease to diagnosis of calculi was 8.8 years (range 0 to 22 years). Calculi were present on the right side in 19 patients and the left side in 19 patients. Stone were composed of calcium oxalate in nine patients, calcium oxalate and calcium phosphate in two patients, and ammonium urate in five patients. The rate of concurrent calculi was significantly higher in ileostomates. The probability of developing calculi was approximately eight times higher for patients with a urine pH of <or=6.0 than for those with a urine pH of >or=6.5.

CONCLUSIONS

The rate of concurrent urolithiasis was higher in patients with a urine pH of <or=6.0, ileostomy, or two or more bowel resections. To prevent formation of calculi, Crohn's disease patients require regular urological examination including urinalysis, ultrasonography, and kidney ureter bladder X-ray.

Metabolic activity of probiotics-oxalate degradation

Urinary tract stones are an important clinical problem in human and veterinary medicine. Hyperoxaluria is the single strongest promoter of kidney stone formation. The aims of the present study were to (a) evaluate oxalate degradation by a range of Bifidobacteria species and Lactobacillus species isolated from the canine and feline gastrointestinal tract in vitro and (b) to determine the impact of oxalate degradation by selected strains in vivo. The bacteria were grown in oxalate-containing media and their ability to degrade oxalate in vitro was determined using reverse-phased HPLC. Bifidobacteria species and Lactobacillus species that degraded oxalate in vitro and survived gastric transit were selected for further examination. The selected probiotics were fed to rats for 4 weeks. Urine was collected at week's 0, 2 and 4 and oxalate levels determined by HPLC. In vitro degradation was detected for 11/18 of the Lactobacillus species. In contrast, the capacity to degrade oxalate was not detected for any of the 13 Bifidobacterium species tested. Lactobacillus animalis 223C, Lactobacillus murinus 1222, L. animalis 5323 and L. murinus 3133 were selected for further investigation in a rat model. Urinary oxalate levels were significantly reduced (p<0.05) in animals fed L. animalis 5323 and L. animalis 223C but were unaltered when fed L. murinus 1222, L. murinus 3133 or placebo. Probiotic organisms vary widely in their capacity to degrade oxalate. In vitro degradation does not uniformly translate to an impact in vivo. The results have therapeutic implications and may influence the choice of probiotic, particularly in the setting of enteric hyperoxaluria.

Use of the frc gene as a molecular marker to characterize oxalate-oxidizing bacterial abundance and diversity structure in soil

Oxalate catabolism, which can have both medical and environmental implications, is performed by phylogenetically diverse bacteria. The formyl-CoA-transferase gene was chosen as a molecular marker of the oxalotrophic function. Degenerated primers were deduced from an alignment of frc gene sequences available in databases. The specificity of primers was tested on a variety of frc-containing and frc-lacking bacteria. The frc-primers were then used to develop PCR-DGGE and real-time SybrGreen PCR assays in soils containing various amounts of oxalate. Some PCR products from pure cultures and from soil samples were cloned and sequenced. Data were used to generate a phylogenetic tree showing that environmental PCR products belonged to the target physiological group. The extent of diversity visualised on DGGE pattern was higher for soil samples containing carbonate resulting from oxalate catabolism. Moreover, the amount of frc gene copies in the investigated soils was detected in the range of 1.64x10(7) to 1.75x10(8)/g of dry soil under oxalogenic tree (representing 0.5 to 1.2% of total 16S rRNA gene copies), whereas the number of frc gene copies in the reference soil was 6.4x10(6) (or 0.2% of 16S rRNA gene copies). This indicates that oxalotrophic bacteria are numerous and widespread in soils and that a relationship exists between the presence of the oxalogenic trees Milicia excelsa and Afzelia africana and the relative abundance of oxalotrophic guilds in the total bacterial communities. This is obviously related to the accomplishment of the oxalate-carbonate pathway, which explains the alkalinization and calcium carbonate accumulation occurring below these trees in an otherwise acidic soil. The molecular tools developed in this study will allow in-depth understanding of the functional implication of these bacteria on carbonate accumulation as a way of atmospheric CO(2) sequestration.

The roles and mechanisms of intestinal oxalate transport in oxalate homeostasis

The mammalian intestine has an important role in the dynamics of oxalate exchange and thereby is significant in the etiology of calcium oxalate nephrolithiasis. Here we review some of the phenomenologic observations that have led to the conclusion that anion exchangers (antiporters) are important mediators of secondarily active, net oxalate transport along the intestine (both absorptive and secretory). Understanding the mechanisms of transepithelial oxalate transport has been advanced radically in recent years by the identification of the solute-linked carrier (SLC)26 family of anion transporters, which has facilitated the identification of specific proteins mediating individual apical or basolateral oxalate transport pathways. Moreover, identification of specific exchangers has underscored their relative importance to oxalate homeostasis as revealed by using knockout mouse models and has facilitated studies of oxalate transport regulation in heterologous expression systems. Finally, the significance of oxalate degrading bacteria to oxalate homeostasis is considered from basic and applied perspectives.

Isolation and some properties of newly isolated oxalate-degradingPandoraeasp. OXJ-11 from soil

AIMS

To isolate and characterize an oxalate-degrading Pandoraea sp. OXJ-11.

METHODS AND RESULTS

A new bacterium Pandoraea sp. OXJ-11 was isolated from soil samples, which can grow in the medium with oxalate as the sole carbon and energy source. The isolate OXJ-11 is Gram-negative straight rod. It occurs singly and is motile by means of a double polar flagellum. Catalase is positive and nitrate is not reduced. It grows aerobically and the optimum growth temperature and the optimum pH are at 30 degrees C and pH 6.0, respectively. The polyphasic taxonomic data along with 16S rRNA sequence comparison demonstrate that the isolate OXJ-11 should belong to the genus Pandoraea and represent a new member in this family.

CONCLUSIONS

Oxalate could be degraded and the oxalate-degrading enzyme activity was detected when the isolate OXJ-11 grew in the medium with oxalate as carbon source.

SIGNIFICANCE AND IMPACT OF THE STUDY

Oxalate-degrading Pandoraea sp. OXJ-11 would be beneficial to the potential application in the control of sclerotinia stem rot in economically important plants caused by fungus Sclerotinia sclerotiorum, and in making plants resistant to the white mold disease by oxalate-degrading enzyme transgene.

Live bacterial cells as orally delivered therapeutics

Despite the swift escalation in research regarding the use of live bacterial cells for therapeutic purposes, the prophylactic and curative use of probiotic microorganisms still remains a wide and controversial field. In addition, the acknowledgement that live bacterial cells can be genetically engineered to synthesise products that have therapeutic potential has generated substantial interest among clinicians and health professionals. Clinical trials have increasingly provided an insightful scientific derivation for the use of live bacterial cells in medicinal practice in diseases such as diarrhoea, cancer, Crohn's disease, enhancement of the host's immune response, and numerous other diseases. A key constraint in the use of live bacterial cells, however, is the complexity of delivering them to the correct target sites. Oral delivery of free live cells, lyophilised cells and immobilised cells has been attempted, but with restricted success, chiefly because bacterial cells are unable to survive passage through the gastrointestinal tract in sufficient dosage. On many occasions, when given orally, these cells have been found to provoke immunogenic responses that are undesirable. Recent studies show that these problems can be overcome by delivering live bacterial cells using artificial cell microcapsules. This review abridges recent developments in the therapeutic use of live bacterial cells, addresses the potential and restrictions for their application in therapy, and provides insights into the future course of this emerging therapy.

Transcriptional and functional analysis of oxalyl-coenzyme A (CoA) decarboxylase and formyl-CoA transferase genes from Lactobacillus acidophilus

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.

Prevention of nephrolithiasis by Lactobacillus in stone-forming rats: a preliminary study

Hyperoxaluria is a risk factor for renal stones. It appears to be sustained by increased dietary load or increased intestinal absorption. The aim of this study was to evaluate whether oral administration of lactobacilli could prevent urolithiasis in stone-forming rats. Oxalate-degrading activities of lactobacilli were evaluated by measuring the oxalate level in a culture medium after inoculation with lactobacilli. Only the strains of Lactobacillus having oxalate-degrading activity were used. Sprague-Dawley rats were fed a powdered standard diet containing 3% sodium oxalate and/or received 100 mg/kg of celecoxib for the first 8 days by gavage, before or after the beginning of this experiment (groups with previous treatment or with co-treatment). Rats were sacrificed after 4 weeks and kidneys were harvested for the assay of crystal formation under a dissecting microscope. Twenty-four-hour urine collections were performed before kidney harvest. Only two strains, Lactobacillus casei HY2743 and L. casei HY7201 out of 31 strains of Lactobacillus were able to degrade oxalate. In both groups of co-treatment and previous treatment with L. casei HY2743 and L. casei HY7201, urine oxalate excretion decreased compared to the group without lactobacilli. The dissecting microscope examination of kidneys in the rats in two previous treatment groups and the co-treatment group with L. casei HY7201 showed less abundant crystals than control groups. Our results show that lactobacilli may be used as a potential therapeutic strategy in the prevention of urinary stones.

Gastrointestinal oxalic acid absorption in calcium-treated rats

We studied whether urinary oxalate excretion after an acute oral load of oxalic acid is influenced by concomitant administration of calcium in rats. Male Wistar rats weighing approximately 180 g were divided into six groups of five animals each. After inducing anesthesia, the animals were orally (via a gastrostomy) given 110 micromol of oxalic acid along with 0, 27.5, 55, 110, or 220 micromol of calcium (0, 27.5, 55, 110, or 220 micromol Ca group, respectively). Saline was given to the control group instead of oxalic acid. Urine specimens were collected before administration and then at hourly intervals up to 5 h afterward. Urinary oxalate and citrate levels were measured by capillary electrophoresis, while urinary calcium, magnesium, and phosphorus levels were measured by ICP spectrophotometry. Urinary oxalate excretion peaked at 1 h after administration and was higher in the 0, 27.5, and 55 micromol Ca groups than in the control group. The urinary recovery of oxalate in these groups was 10-15%, while the recovery rate was less than 3% in other groups. Urinary Ca excretion showed no significant changes, either over time or between groups. Free oxalic acid is absorbed more readily from the gastrointestinal tract than calcium oxalate, while simultaneous administration of calcium appears to block intestinal oxalic acid absorption in a dose-dependent manner.

Oxalate degrading bacteria: new treatment option for patients with primary and secondary hyperoxaluria?

Current treatment options in patients with primary and secondary hyperoxaluria are limited and do not always lead to sufficient reduction in urinary oxalate excretion. Intestinal oxalate degrading bacteria are capable of degrading oxalate to CO(2) and formate, the latter being further metabolized and excreted via the feces. It is speculated, that both endogenously produced, as well as dietary oxalate can be significantly removed via the intestinal tract. Oxalobacter formigenes, an obligate anaerobic microbe normally found in the intestinal tract has one oxalate degrading enzyme, oxalyl-CoA decarboxylase, which is also found in Bifidobacterium lactis. Other bacteria with possible oxalate degrading potency are lactic acid bacteria, as well as Enterococcus faecalis and Eubacterium lentum. However, specific therapeutic studies on humans are scarce and, except for Oxalobacter, data are not congruent. We found the oral application of Oxalobacter successful in patients with primary hyperoxaluria. However, long-term post-treatment follow-up of 1-2 years showed that constant intestinal colonization is not achieved in most patients. In one patient with constant colonization, urinary oxalate excretion normalized over time. Short-term studies with other bacteria such as lactic acid bacteria did not show a specific reduction in urinary oxalate excretion. O. formigenes might be a promising new therapeutic tool in patients with primary and secondary hyperoxaluria.

Oxalate-degrading Providencia rettgeri isolated from human stools

BACKGROUND

Oxalate-degrading bacteria are thought to metabolize intestinal oxalate and thus decrease the urinary excretion of oxalate by reducing its intestinal absorption.

METHODS

We have isolated several novel oxalate-degrading bacteria from human stools. Oxalate degrading bacteria were investigated to characterize their protein profiles with antibodies against oxalyl-coenzyme A decarboxylase (65 kDa) and formyl-coenzyme A transferase (48 kDa) purified from Oxalobacter formigenes.

RESULTS

One of these isolates was identified as Providencia rettgeri, which showed two proteins (65 kDa and 48 kDa) on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) that were not found in non-oxalate-degrading P. rettgeri. Antibodies reacted with the 65 and 48 kDa proteins from the P. rettgeri strain on Western blotting. An Oxalobacter formigenes formyl-coenzyme A transferase gene probe reacted with chromosomal DNA from P. rettgeri on Southern blotting under high stringency conditions, while an Oxalobacter formigenes oxalyl-coenzyme A decarboxylase gene probe did not react under the same conditions.

CONCLUSIONS

The mechamism of oxalate degradation by P. rettgeri appears to be similar to that of Oxalobacter formigenes. This is the first report of a facultative oxalate-degrading organism that is one of the Enterobacteriaceae.

Absorptive hyperoxaluria leads to an increased risk for urolithiasis or nephrocalcinosis in cystic fibrosis

BACKGROUND

Hyperoxaluria has been incriminated to account for the increased incidence of urolithiasis or nephrocalcinosis in patients with cystic fibrosis (CF). Hyperoxaluria presumably is caused by fat malabsorption and the absence of such intestinal oxalate-degrading bacteria as Oxalobacter formigenes. To better elucidate its pathophysiological characteristics, we prospectively studied patients with CF by determining these parameters and performing renal ultrasonography twice yearly.

METHODS

In addition to routine tests in urine (lithogenic and stone-inhibitory substances), the presence of O formigenes was tested in stool, plasma oxalate was measured, and a [13C2]oxalate absorption test was performed in 37 patients with CF aged 5 to 37 years (15 females, 22 males) who were constantly hyperoxaluric before the study.

RESULTS

Hyperoxaluria (oxalate, 46 to 141 mg/1.73 m2/24 h [0.51 to 1.57 mmol/1.73 m2/24 h]; normal, < 45 mg/1.73 m2/24 h [< 0.5 mmol/1.73 m2/24 h]) was now found in 24 patients (64.8%). Plasma oxalate levels were elevated in 6 patients (7.92 to 19.5 micromol/L; normal, 6.3 +/- 1.1 micromol/L). Oxalobacter species were detected in only 1 patient. Intestinal oxalate absorption was elevated (11.4% to 28.5%; normal, < 10%) in 23 patients. Hypocitraturia was present in 17 patients (citrate, 0.35 to 2.8 g/1.73 m2/24 h [0.2 to 1.1 mmol/1.73 m2/24 h]; normal female, > 2.8 mg/1.73 m2/24 h [> 1.6 mmol/1.73 m2/24 h]; male, > 3.3 mg/1.73 m2/24 h [> 1.9 mmol/1.73 m2/24 h]). Urine calcium oxalate saturation was elevated in 17 patients (5.62 to 28.9 relative units; normal female, < 5.5 relative units; male, < 6.3 relative units). In 16% of patients, urolithiasis (n = 2) or nephrocalcinosis (n = 4) was diagnosed ultrasonographically.

CONCLUSION

Absorptive hyperoxaluria and hypocitraturia are the main culprits for the increased incidence of urolithiasis and nephrocalcinosis in patients with CF. We advocate high fluid intake, low-oxalate/high-calcium diet, and alkali citrate medication, if necessary. Additional studies are necessary to determine the influence of Oxalobacter species or other oxalate-degrading bacteria on oxalate handling in patients with CF.

Oxalate, calcium and ash intake and excretion balances in fat sand rats (Psammomys obesus) feeding on two different diets

Fat sand rats Psammomys obesus feed exclusively on plants of the family Chenopodiaceae, which contain high concentrations of chloride salts (NaCl, KCl) and oxalate salts. Ingestion of large quantities of oxalate is challenging for mammals because oxalate chelates Ca(2+) cations, reducing Ca(2+) availability. Oxalate is a metabolic end-point in mammalian metabolism, however it can be broken-down by intestinal bacteria. We predicted that in fat sand rats microbial breakdown of oxalate will be substantial due to the high dietary load. In addition, since a high concentration of soluble chloride salts increases the solubility of calcium oxalate in solution, we examined whether a change in the intake of chloride salts affects microbial oxalate breakdown and calcium excretion in fat sand rats. We measured oxalate, calcium and other inorganic matter (ash) intake and excretion in fat sand rats feeding on two different diets: saltbush (Atriplex halimus), their natural diet, and goose-foot (Chenopodium album), a non-native chenopod on which fat sand rats will readily feed and that has a similar oxalate content to saltbush but only 2/3 of the ash content. In animals feeding on both diets, 65-80% of the oxalate ingested did not appear in urine or faeces. In animals consuming the more saline saltbush, significantly more oxalate was apparently degraded (p<0.001), while significantly less oxalate was excreted in urine (p<0.01) and in faeces (p<0.05). We propose, therefore, that fat sand rats rely on symbiotic bacteria to remove a large portion of the oxalates ingested with their diet, and that the high dietary salt intake may play a beneficial role in their oxalate and calcium metabolism.

Artificial Cell Therapy: New Strategies for the Therapeutic Delivery of Live Bacteria

There has been rapid growth in research regarding the use of live bacterial cells for therapeutic purposes. The recognition that these cells can be genetically engineered to synthesize products that have therapeutic potential has generated considerable interest and excitement among clinicians and health professionals. It is expected that a wide range of disease modifying substrates such as enzymes, hormones, antibodies, vaccines, and other genetic products will be used successfully and will impact upon health care substantially. However, a major limitation in the use of these bacterial cells is the complexity of delivering them to the correct target tissues. Oral delivery of live cells, lyophilized cells, and immobilized cells has been attempted but with limited success. Primarily, this is because bacterial cells are incapable of surviving passage through the gastrointestinal tract. In many occasions, when given orally, these cells have been found to provoke immunogenic responses that are undesirable. Recent studies show that these problems can be overcome by delivering live bacterial cells, such as genetically engineered cells, using artificial cell microcapsules. This review summarizes recent advances in the therapeutic use of live bacterial cells for therapy, discusses the principles of using artificial cells for the oral delivery of bacterial cells, outlines methods for preparing suitable artificial cells for this purpose, addresses potentials and limitations for their application in therapy, and provides insight for the future direction of this emergent and highly prospective technology.

Characterization and heterologous expression of the oxalyl coenzyme A decarboxylase gene from Bifidobacterium lactis

Oxalyl coenzyme A (CoA) decarboxylase (Oxc) is a key enzyme in the catabolism of the highly toxic compound oxalate, catalyzing the decarboxylation of oxalyl-CoA to formyl-CoA. The gene encoding a novel oxalyl-CoA decarboxylase from Bifidobacterium lactis DSM 10140 (oxc) was identified and characterized. This strain, isolated from yogurt, showed the highest oxalate-degrading activity in a preliminary screening with 12 strains belonging to Bifidobacterium, an anaerobic intestinal bacterial group largely used in probiotic products. The oxc gene was isolated by probing a B. lactis genomic library with a probe obtained by amplification of the oxalyl-CoA decarboxylase gene from Oxalobacter formigenes, an anaerobic bacterium of the human intestinal microflora. The oxc DNA sequence analysis revealed an open reading frame of 1,773 bp encoding a deduced 590-amino-acid protein with a molecular mass of about 63 kDa. Analysis of amino acid sequence showed a significant homology (47%) with oxalyl-CoA decarboxylase of O. formigenes and a typical thiamine pyrophosphate-binding site that has been reported for several decarboxylase enzymes. Primer extension experiments with oxc performed by using RNA isolated from B. lactis identified the transcriptional start site 28 bp upstream of the ATG start codon, immediately adjacent to a presumed promoter region. The protein overexpressed in Escherichia coli cross-reacted with an anti-O. formigenes oxalyl-CoA decarboxylase antibody. Enzymatic activity, when evaluated by capillary electrophoresis analysis, demonstrated that the consumption substrate oxalyl-CoA was regulated by a product inhibition of the enzyme. These findings suggest a potential role for Bifidobacterium in the intestinal degradation of oxalate.

Intestinal transport of an obdurate anion: oxalate

In this review, we focus on the role of gastrointestinal transport of oxalate primarily from a contemporary physiological standpoint with an emphasis on those aspects that we believe may be most important in efforts to mitigate the untoward effects of oxalate. Included in this review is a general discussion of intestinal solute transport as it relates to oxalate, considering cellular and paracellular avenues, the transport mechanisms, and the molecular identities of oxalate transporters. In addition, we review the role of the intestine in oxalate disease states and various factors affecting oxalate absorption.