Ethanolamine enhances adhesion, promotes microcompartment formation, and modulates gene expression in Levilactobacillus brevis ATCC 14869.

Ethanolamine is an abundant compound in the gastrointestinal tract and a valuable source of carbon and nitrogen for pathogenic bacteria harboring ethanolamine utilization (eut) genes. Eut-positive pathogens can consume free ethanolamine to outcompete commensal microbes, which often lack eut genes, and establish infection. Ethanolamine can also act as a host recognition signal for eut-positive pathogens to upregulate virulence genes during colonization. Therefore, reducing free ethanolamine titers may represent a novel approach to preventing infection by eut-positive pathogens. Interestingly, the commensal microorganism Levilactobacillus brevis ATCC 14869 was found to encode over 18 eut genes within its genome. This led us to hypothesize that L. brevis can compete with eut-positive pathogens by clearing free ethanolamine from the environment. Our results demonstrate that despite being unable to metabolize ethanolamine under most conditions, L. brevis ATCC 14869 responds to the compound by increasing the expression of genes encoding proteins involved in microcompartment formation and adhesion to the intestinal epithelial barrier. The improved intestinal adhesion of L. brevis in the presence of ethanolamine also enhanced the exclusion of eut-positive pathogens from adhering to intestinal epithelial cells. These findings support further studies to test whether L. brevis ATCC 14869 can counter enteric pathogens and prevent or reduce the severity of infections. Overall, the metabolic capabilities of L. brevis ATCC 14869 offer a unique opportunity to add to the armamentarium of antimicrobial therapies as well as our understanding of the mechanisms used by beneficial microbes to sense and adapt to host microenvironments.

Corrigendum: New perspectives on an old grouping: the genomic and phenotypic variability of Oxalobacter formigenes and the implications for calcium oxalate stone prevention.

[This corrects the article DOI: 10.3389/fmicb.2022.1011102.].

Vitamins as regulators of calcium-containing kidney stones - new perspectives on the role of the gut microbiome.

Calcium-based kidney stone disease is a highly prevalent and morbid condition, with an often complicated and multifactorial aetiology. An abundance of research on the role of specific vitamins (B6, C and D) in stone formation exists, but no consensus has been reached on how these vitamins influence stone disease. As a consequence of emerging research on the role of the gut microbiota in urolithiasis, previous notions on the contribution of these vitamins to urolithiasis are being reconsidered in the field, and investigation into previously overlooked vitamins (A, E and K) was expanded. Understanding how the microbiota influences host vitamin regulation could help to determine the role of vitamins in stone disease.

Osteopontin phosphopeptide mitigates calcium oxalate stone formation in a Drosophila melanogaster model.

Kidney stone disease affects nearly one in ten individuals and places a significant economic strain on global healthcare systems. Despite the high frequency of stones within the population, effective preventative strategies are lacking and disease prevalence continues to rise. Osteopontin (OPN) is a urinary protein that can inhibit the formation of renal calculi in vitro. However, the efficacy of OPN in vivo has yet to be determined. Using an established Drosophila melanogaster model of calcium oxalate urolithiasis, we demonstrated that a 16-residue synthetic OPN phosphopeptide effectively reduced stone burden in vivo. Oral supplementation with this peptide altered crystal morphology of calcium oxalate monohydrate (COM) in a similar manner to previous in vitro studies, and the presence of the OPN phosphopeptide during COM formation and adhesion significantly reduced crystal attachment to mammalian kidney cells. Altogether, this study is the first to show that an OPN phosphopeptide can directly mitigate calcium oxalate urolithiasis formation in vivo by modulating crystal morphology. These findings suggest that OPN supplementation is a promising therapeutic approach and may be clinically useful in the management of urolithiasis in humans.

Probiotic Bifidobacteria Mitigate the Deleterious Effects of para-Cresol in a Drosophila melanogaster Toxicity Model.

Renal impairment associated with chronic kidney disease (CKD) causes the buildup of uremic toxins that are deleterious to patient health. Current therapies that manage toxin accumulation in CKD offer an incomplete therapeutic effect against toxins such as para-cresol (p-cresol) and p-cresyl sulfate. Probiotic therapies can exploit the wealth of microbial diversity to reduce toxin accumulation. Using in vitro culture techniques, strains of lactobacilli and bifidobacteria from a 24-strain synbiotic were investigated for their ability to remove p-cresol. Four strains of bifidobacteria internalized p-cresol from the extracellular environment. The oral supplementation of these toxin-clearing probiotics was more protective than control strains in a Drosophila melanogaster toxicity model. Bifidobacterial supplementation was also associated with higher abundance of lactobacilli in the gut microbiota of p-cresol-exposed flies. The present findings suggest that these strains might reduce p-cresol in the gut in addition to increasing the prevalence of other beneficial bacteria, such as lactobacilli, and should be tested clinically to normalize the dysbiotic gut microbiota observed in CKD patients. IMPORTANCE Chronic kidney disease (CKD) affects approximately 10% of the global population and has limited treatment options. The accumulation of gut microbiota-derived uremic toxins, such as para-cresol (p-cresol) and p-cresyl sulfate, is associated with the onset of comorbidities (i.e., atherosclerosis and cognitive disorders) in CKD. Unfortunately, dialysis, the gold standard therapy is unable to remove these toxins from the bloodstream due to their highly protein-bound nature. Some strains of Bifidobacterium have metabolic properties that may be useful in managing uremic toxicity. Using a Drosophila model, the present work highlights why dosing with certain probiotic strains may be clinically useful in CKD management.

Long-Duration Space Travel Support Must Consider Wider Influences to Conserve Microbiota Composition and Function.

The microbiota is important for immune modulation, nutrient acquisition, vitamin production, and other aspects for long-term human health. Isolated model organisms can lose microbial diversity over time and humans are likely the same. Decreasing microbial diversity and the subsequent loss of function may accelerate disease progression on Earth, and to an even greater degree in space. For this reason, maintaining a healthy microbiome during spaceflight has recently garnered consideration. Diet, lifestyle, and consumption of beneficial microbes can shape the microbiota, but the replenishment we attain from environmental exposure to microbes is important too. Probiotics, prebiotics, fermented foods, fecal microbiota transplantation (FMT), and other methods of microbiota modulation currently available may be of benefit for shorter trips, but may not be viable options to overcome the unique challenges faced in long-term space travel. Novel fermented food products with particular impact on gut health, immune modulation, and other space-targeted health outcomes are worthy of exploration. Further consideration of potential microbial replenishment to humans, including from environmental sources to maintain a healthy microbiome, may also be required.

Why Are Bifidobacteria Important for Infants?

The presence of Bifidobacterium species in the maternal vaginal and fecal microbiota is arguably an evolutionary trait that allows these organisms to be primary colonizers of the newborn intestinal tract. Their ability to utilize human milk oligosaccharides fosters their establishment as core health-promoting organisms throughout life. A reduction in their abundance in infants has been shown to increase the prevalence of obesity, diabetes, metabolic disorder, and all-cause mortality later in life. Probiotic strains have been developed as supplements for premature babies and to counter some of these ailments as well as to confer a range of health benefits. The ability to modulate the immune response and produce short-chain fatty acids, particularly acetate and butyrate, that strengthen the gut barrier and regulate the gut microbiome, makes Bifidobacterium a core component of a healthy infant through adulthood.

New perspectives on an old grouping: The genomic and phenotypic variability of Oxalobacter formigenes and the implications for calcium oxalate stone prevention.

Oxalobacter formigenes is a unique bacterium with the ability to metabolize oxalate as a primary carbon source. Most kidney stones in humans are composed of calcium and oxalate. Therefore, supplementation with an oxalate-degrading bacterium may reduce stone burden in patients suffering from recurrent calcium oxalate-based urolithiasis. Strains of O. formigenes are divided into two groups: group I and group II. However, the differences between strains from each group remain unclear and elucidating these distinctions will provide a better understanding of their physiology and potential clinical applications. Here, genomes from multiple O. formigenes strains underwent whole genome sequencing followed by phylogenetic and functional analyses. Genetic differences suggest that the O. formigenes taxon should be divided into an additional three species: Oxalobacter aliiformigenes sp. nov, Oxalobacter paeniformigenes sp. nov, and Oxalobacter paraformigenes sp. nov. Despite the similarities in the oxalyl-CoA gene (oxc), which is essential for oxalate degradation, these strains have multiple unique genetic features that may be potential exploited for clinical use. Further investigation into the growth of these strains in a simulated fecal environment revealed that O. aliiformigenes strains are capable of thriving within the human gut microbiota. O. aliiformigenes may be a better therapeutic candidate than current group I strains (retaining the name O. formigenes), which have been previously tested and shown to be ineffective as an oral supplement to mitigate stone disease. By performing genomic analyses and identifying these novel characteristics, Oxalobacter strains better suited to mitigation of calcium oxalate-based urolithiasis may be identified in the future.

High-Throughput in vitro Gel-Based Plate Assay to Screen for Calcium Oxalate Stone Inhibitors.

OBJECTIVE: Kidney stones are a common medical condition that is increasing in prevalence worldwide. Approximately, ∼80% of urinary calculi are composed of calcium oxalate (CaOx). There is a growing interest toward identifying therapeutic compounds that can inhibit the formation of CaOx crystals. However, some chemicals (e.g., antibiotics and bacterial metabolites) may directly promote crystallization. Current knowledge is limited regarding crystal promoters and inhibitors. Thus, we have developed an in vitro gel-based diffusion model to screen for substances that directly influence CaOx crystal formation. MATERIALS AND METHODS: We used double diffusion of sodium oxalate and calcium chloride-loaded paper disks along an agar medium to facilitate the controlled formation of monohydrate and dihydrate CaOx crystals. A third disk was used for the perpendicular diffusion of a test substance to assess its influence on CaOx crystal formation. RESULTS: We confirmed that citrates and magnesium are effective inhibitors of CaOx crystals. We also demonstrated that 2 strains of uropathogenic Escherichia coli are able to promote crystal formation. While the other tested uropathogens and most antibiotics did not change crystal formation, ampicillin was able to reduce crystallization. CONCLUSION: We have developed an inexpensive and high-throughput model to evaluate substances that influence CaOx crystallization.