Tomato Plant Microbiota under Conventional and Organic Fertilization Regimes in a Soilless Culture System.

Tomato is the main vegetable cultivated under soilless culture systems (SCSs); production of organic tomato under SCSs has increased due to consumer demands for healthier and environmentally friendly vegetables. However, organic tomato production under SCSs has been associated with low crop performance and fruit quality defects. These agricultural deficiencies could be linked to alterations in tomato plant microbiota; nonetheless, this issue has not been sufficiently addressed. Thus, the main goal of the present study was to characterize the rhizosphere and phyllosphere of tomato plants cultivated under conventional and organic SCSs. To accomplish this goal, tomato plants grown in commercial greenhouses under conventional or organic SCSs were tested at 8, 26, and 44 weeks after seedling transplantation. Substrate (n = 24), root (n = 24), and fruit (n = 24) composite samples were subjected to DNA extraction and high-throughput 16S rRNA gene sequencing. The present study revealed that the tomato core microbiota was predominantly constituted by Proteobacteria, Actinobacteria, and Firmicutes. Remarkably, six bacterial families, Bacillaceae, Microbacteriaceae, Nocardioidaceae, Pseudomonadaceae, Rhodobacteraceae, and Sphingomonadaceae, were shared among all substrate, rhizosphere, and fruit samples. Importantly, it was shown that plants under organic SCSs undergo a dysbiosis characterized by significant changes in the relative abundance of Bradyrhizobiaceae, Caulobacteraceae, Chitinophagaceae, Enterobacteriaceae, Erythrobacteraceae, Flavobacteriaceae, Nocardioidaceae, Rhodobacteraceae, and Streptomycetaceae. These results suggest that microbial alterations in substrates, roots, and fruits could be potential factors in contributing to the crop performance and fruit quality deficiencies observed in organic SCSs.

The role of the SNF1 signaling pathway in the growth of Saccharomyces cerevisiae in different carbon and nitrogen sources.

Cancer is a leading cause of death worldwide, reporting nearly 10 million deaths in 2020. One of the hallmarks of cancer cells is their capability to evade growth suppressors and sustain proliferative signaling resulting in uncontrolled growth. The AMPK pathway, a catabolic via to economize ATP, has been associated with cancer. AMPK activation is related to cancer progression in advanced stages, while its activation by metformin or phenformin is associated with cancer chemoprevention. Thus, the role of the AMPK pathway in cancer growth modulation is not clear. Saccharomyces cerevisiae might be a useful model to elucidate AMPK participation in growth regulation since it shares a highly conserved AMPK pathway. Therefore, this work is aimed at evaluating the role of the AMPK pathway on S. cerevisiae growth under different nutritional conditions. Herein, we provide evidence that the SNF1 gene is necessary to maintain S. cerevisiae growth with glucose as a sole carbon source at every concentration tested. Resveratrol supplementation inhibited the exponential growth of snf1∆ strain at low glucose levels and decreased it at high glucose levels. SNF1 gene deletion impaired exponential growth in a carbohydrate concentration-dependent manner independently of nitrogen source or concentration. Interestingly, deletion of genes encoding for upstream kinases (SAK1, ELM1, and TOS3) also had a glucose dose-dependent effect upon exponential growth. Furthermore, gene deletion of regulatory subunits of the AMPK complex impacted exponential growth in a glucose-dependent manner. Altogether, these results suggest that the SNF1 pathway affects the exponential growth of S. cerevisiae in a glucose-dependent manner.

Snf1p/Hxk2p/Mig1p pathway regulates hexose transporters transcript levels, affecting the exponential growth and mitochondrial respiration of Saccharomyces cerevisiae.

The Crabtree effect molecular regulation comprehension could help to improve ethanol production with biotechnological purposes and a better understanding of cancer etiology due to its similarity with the Warburg effect. Snf1p/Hxk2p/Mig1p pathway has been linked with the transcriptional regulation of the hexose transporters and phenotypes associated with the Crabtree effect. Nevertheless, direct evidence linking the genetic control of the hexose transporters with modulation of the Crabtree effect phenotypes by the Snf1p/Hxk2p/Mig1p pathway is still lacking. In this sense, we provide evidence that SNF1 and HXK2 genes deletion affects exponential growth, mitochondrial respiration, and transcript levels of hexose transporters in a glucose-dependent manner. The Vmax of the hexose transporters with the high transcript levels was correlated positively with the exponential growth and negatively with the mitochondrial respiration. HXT2 gene transcript levels were the most affected by the deletion of the SNF1/HXK2/MIG1 pathway. Deleting the orthologous genes SNF1 and HXK2 in Kluyveromyces marxianus (Crabtree negative yeast) has an opposite effect compared to Saccharomyces cerevisiae in growth and mitochondrial respiration. Overall, these results indicate that the SNF1/HXK2/MIG1 pathway regulates transcript levels of the hexose transporters, which shows an association with the exponential growth and mitochondrial respiration in a glucose-dependent manner.

Metabolic profile of the Warburg effect as a tool for molecular prognosis and diagnosis of cancer.

INTRODUCTION: Adaptations of eukaryotic cells to environmental changes are important for their survival. However, under some circumstances, microenvironmental changes promote that eukaryotic cells utilize a metabolic signature resembling a unicellular organism named the Warburg effect. Most cancer cells share the Warburg effect displaying lactic fermentation and high glucose uptake. The Warburg effect also induces a metabolic rewiring stimulating glutamine consumption and lipid synthesis, also considered cancer hallmarks. Amino acid metabolism alteration due to the Warburg effect increases plasma levels of proline and branched-chain amino acids in several cancer types. Proline and lipids are probably used as electron transfer molecules in carcinogenic cells. In addition, branched-chain amino acids fuel the Krebs cycle, protein synthesis, and signaling in cancer cells. AREAS COVERED: This review covers how metabolomics studies describe changes in some metabolites and proteins associated with the Warburg effect and related metabolic pathways. EXPERT OPINION: In this review, we analyze the metabolic signature of the Warburg effect and related phenotypes and propose some Warburg effect-related metabolites and proteins (lactate, glucose uptake, glucose transporters, glutamine, branched-chain amino acids, proline, and some lipogenic enzymes) as promising cancer biomarkers.

Resveratrol shortens the chronological lifespan of Saccharomyces cerevisiae by a pro-oxidant mechanism.

The antioxidant phenotype caused by resveratrol has been recognized as a key piece in the health benefits exerted by this phytochemical in diseases related to aging. It has recently been proposed that a mitochondrial pro-oxidant mechanism could be the cause of resveratrol antioxidant properties. In this regard, the hypothesis that resveratrol impedes electron transport to complex III of the electron transport chain as its main target suggests that resveratrol could increase reactive oxygen species (ROS) generation through reverse electron transport or by the semiquinones formation. This idea also explains that cells respond to resveratrol oxidative damage, inducing their antioxidant systems. Moreover, resveratrol pro-oxidant properties could accelerate the aging process, according to the free radical theory of aging, which postulates that organism's age due to the accumulation of the harmful effects of ROS in cells. Nonetheless, there is no evidence linking the chronological lifespan (CLS) shorten occasioned by resveratrol with a pro-oxidant mechanism. Hence, this study aimed to evaluate whether resveratrol shortens the CLS of Saccharomyces cerevisiae due to a pro-oxidant activity. Herein, we provide evidence that supplementation with 100 µM of resveratrol at 5% glucose: (1) shortened the CLS of ctt1Δ and yap1Δ strains; (2) decreased ROS levels and increased the catalase activity in WT strain; (3) maintained unaffected the ROS levels and did not change the catalase activity in ctt1Δ strain; and (4) lessened the exponential growth of ctt1Δ strain, which was restored with the adding of reduced glutathione. These results indicate that resveratrol decreases CLS by a pro-oxidant mechanism.

A Comprehensive Evaluation of Enterobacteriaceae Primer Sets for Analysis of Host-Associated Microbiota.

Enterobacteriaceae is one of the most important bacterial groups within the Proteobacteria phylum. This bacterial group includes pathogens, commensal and beneficial populations. Numerous 16S rRNA gene PCR-based assays have been designed to analyze Enterobacteriaceae diversity and relative abundance, and, to the best of our knowledge, 16 primer pairs have been validated, published and used since 2003. Nonetheless, a comprehensive performance analysis of these primer sets has not yet been carried out. This information is of particular importance due to the recent taxonomic restructuration of Enterobacteriaceae into seven bacterial families. To overcome this lack of information, the identified collection of primer pairs (n = 16) was subjected to primer performance analysis using multiple bioinformatics tools. Herein it was revealed that, based on specificity and coverage of the 16S rRNA gene, these 16 primer sets could be divided into different categories: Enterobacterales-, multi-family-, multi-genus- and Enterobacteriaceae-specific primers. These results highlight the impact of taxonomy changes on performance of molecular assays and data interpretation. Moreover, they underline the urgent need to revise and update the molecular tools used for molecular microbial analyses.

Gut Bacterial Families Are Associated with Body Composition and Metabolic Risk Markers in School-Aged Children in Rural Mexico.

Background: Differences in gut microbiota composition have been associated with obesity and metabolic alterations in children. The aim of this study was to analyze the abundance of the main bacterial families of the gut among children according to their body composition and metabolic markers. Methods: A cross-sectional study was conducted with 93 school-aged children (8.4 ± 1.6 years old). Anthropometric and body composition variables were measured and a blood sample was collected to determine glucose, insulin, lipid profile, C-reactive protein, leptin, and cytokines [interleukin 6, interleukin 10 (IL-10), tumor necrosis factor α (TNFα)]. DNA was extracted from stool samples and the abundance of bacterial families (Bacteroidaceae-Porphyromonadaceae-Prevotellaceae, Lactobacillaceae, Enterococcaceae, and Lachnospiraceae-Ruminococcaceae) was determined by qPCR assays. Results: Children with obesity and high waist/height ratio had lower Bacteroidaceae-Porphyromonadaceae-Prevotellaceae and higher abundance of Lactobacillaceae when compared with normal-weight children. TNFα was negatively associated and IL-10 was positively associated with Bacteroidaceae-Porphyromonadaceae-Prevotellaceae. Triglycerides showed a positive relationship with Lachnospiraceae-Ruminococcaceae whereas high-density lipoprotein-cholesterol was negatively associated with Lactobacillaceae. Conclusion: In rural Mexican school-aged children, a low abundance of Bacteroidaceae-Porphyromonadaceae-Prevotellaceae and a high abundance of Lactobacillaceae are associated with obesity and metabolic disturbances.

A Molecular Tool for Rapid Detection and Traceability of Cyclospora cayetanensis in Fresh Berries and Berry Farm Soils.

Due to recent outbreaks of cyclosporiasis associated with consumption of fresh berries, producers are demanding modern microbiological tools for the rapid and accurate identification of the human pathogen Cyclospora cayetanensis in berries and environmental samples. The aim of the present work was to develop a molecular tool based on a PCR approach for the rapid and accurate detection of C. cayetanensis. A nested PCR assay was validated for the amplification of a 294 bp size region of the 18S rRNA gene from C. cayetanensis. The limit of detection for the nested PCR assay was validated using 48 berry samples spiked with ~0, 10, 100, and 1000 oocyst per gram of sample. With this assay, it was possible to detect as few as 1 oocyst per gram of berry, in a 50 g sample. Sanger DNA sequencing and phylogenetic analysis were carried out to confirm the presence of C. cayetanensis in berry (n = 17) and soil (n = 5) samples. The phylogenetic analysis revealed that the C. cayetanensis sequences obtained from Mexico clustered within a group recovered from China, Peru, Guatemala-Haiti, and Japan. The PCR protocol designed in the present study could be an important tool for the rapid and accurate detection of this human pathogen in environmental and food samples.

Three-Year Longitudinal Study: Prevalence of Salmonella Enterica in Chicken Meat is Higher in Supermarkets Than Wet Markets from Mexico.

Worldwide, chicken meat is considered one of the main sources of Salmonella enterica in humans. To protect consumers from this foodborne pathogen, international health authorities recommend the establishment of continuous Salmonella surveillance programs in meat. However, these programs are scarce in many world regions; thus, the goal of the present study was to perform a longitudinal surveillance of S. enterica in chicken meat in Mexico. A total of 1160 samples were collected and analyzed monthly from 2016 to 2018 in ten chicken meat retailers (supermarkets and wet markets) located in central Mexico. The isolation and identification of S. enterica was carried out using conventional and molecular methods. Overall, S. enterica was recovered from 18.1% (210/1160) of the chicken meat samples. Remarkably, during the three years of evaluation, S. enterica was more prevalent (P < 0.0001) in supermarkets (27.2%, 158/580) than in wet markets (9.0%, 52/580). The study was 3.8 times more likely (odds ratio = 3.8, P < 0.0001) to recover S. enterica from supermarkets than wet markets. Additionally, a higher prevalence (P < 0.05) of this pathogen was observed during the spring, summer, autumn, and winter in supermarkets compared with wet markets. Moreover, the recovery rate of S. enterica from supermarkets showed a gradual increase from 20.78% to 42% (P < 0.0001) from 2016 to 2018. Interestingly, no correlation (P > 0.05) was observed between the S. enterica recovery rate in chicken meat and reported cases of Salmonella infections in humans. Higher levels of S. enterica in chicken meat retailed in supermarkets are not unusual; this phenomenon has also been reported in some European and Asian countries. Together, these results uncover an important health threat that needs to be urgently addressed by poultry meat producers and retailers.

Insights into the Identification of the Specific Spoilage Organisms in Chicken Meat.

Poultry meat deterioration is caused by environmental conditions, as well as proliferation of different bacterial groups, and their interactions. It has been proposed that meat spoilage involves two bacterial groups: one group that initiates the deterioration process, known as specific spoilage organisms (SSOs), and the other known as spoilage associated organisms (SAOs) which represents all bacteria groups recovered from meat samples before, during, and after the spoilage process. Numerous studies have characterized the diversity of chicken meat SAOs; nonetheless, the identification of the SSOs remains a long-standing question. Based on recent genomic studies, it is suggested that the SSOs should possess an extensive genome size to survive and proliferate in raw meat, a cold, complex, and hostile environment. To evaluate this hypothesis, we performed comparative genomic analyses in members of the meat microbiota to identify microorganisms with extensive genome size and ability to cause chicken meat spoilage. Our studies show that members of the Pseudomonadaceae family have evolved numerous biological features such as large genomic size, slow-growing potential, low 16S rRNA copy number, psychrotrophic, and oligotrophic metabolism to initiate the spoilage of poultry meat. Moreover, inoculation experiments corroborated that these biological traits are associated with the potential to cause chicken meat deterioration. Together, these results provide new insights into the identification of SSO. Further studies are in progress to elucidate the impact of the SSO on meat quality and microbiota diversity.

Comparison of the bioactive potential of Roselle (Hibiscus sabdariffa L.) calyx and its by-product: Phenolic characterization by UPLC-QTOF MSE and their anti-obesity effect in vivo.

The aim of the present study was to evaluate extractable (EPP), non-extractable polyphenols (NEPP) and organic acid in Roselle by-product, as well as its potential health beneficial effects in obesity control and their complication in rats fed with high caloric diet. Roselle by-product showed a higher content of dietary fiber and NEPP than Roselle calix, which was was a better source of EPP (P < .05). The UPLC-QTOF MSE analysis allowed the tentative identification of 34 EPP, and 3 hydrolysable polyphenols (NEPP), and 2 organic acids in calyx and by-product. Rats fed with a high caloric diet supplemented with 4% of dietary fiber from by-products and Roselle calyx powder generated a reduction in body weight gain (10% and 14%), adipocytes hypertrophy (17% and 13%) and insulin resistance (48% and 59%) and hepatic steatosis (15% and 25%; respectively) compared with rats fed with a high caloric diet alone. Interestingly, even though Roselle by-product has low EPP contents showed comparable beneficial health effects than Roselle calyces. These effects could be associated with high content of dietary fiber and NEPP. Together, the results of the present study indicate that Roselle by-products could be a potential ingredient to develop functional foods against obesity and its complications.

An Improve Protocol for PCR Using LM1 and LM2 Primers for Listeria monocytogenes Detection in Food Matrices.

Several studies have observed that a conventional PCR protocol using primers LM1 and LM2 for the identification of gene hlyA Listeria monocytogenes generates non-specific PCR amplifications and false positives. For this reason in this study, we provide a modified PCR protocol that improves the specificity of the LM1 and LM2 primers.

Resveratrol induces mitochondrial dysfunction and decreases chronological life span of Saccharomyces cerevisiae in a glucose-dependent manner.

A broad range of health benefits have been attributed to resveratrol (RSV) supplementation in mammalian systems, including the increases in longevity. Nonetheless, despite the growing number of studies performed with RSV, the molecular mechanism by which it acts still remains unknown. Recently, it has been proposed that inhibition of the oxidative phosphorylation activity is the principal mechanism of RSV action. This mechanism suggests that RSV might induce mitochondrial dysfunction resulting in oxidative damage to cells with a concomitant decrease of cell viability and cellular life span. To prove this hypothesis, the chronological life span (CLS) of Saccharomyces cerevisiae was studied as it is accepted as an important model of oxidative damage and aging. In addition, oxygen consumption, mitochondrial membrane potential, and hydrogen peroxide (H2O2) release were measured in order to determine the extent of mitochondrial dysfunction. The results demonstrated that the supplementation of S. cerevisiae cultures with 100 µM RSV decreased CLS in a glucose-dependent manner. At high-level glucose, RSV supplementation increased oxygen consumption during the exponential phase yeast cultures, but inhibited it in chronologically aged yeast cultures. However, at low-level glucose, oxygen consumption was inhibited in yeast cultures in the exponential phase as well as in chronologically aged cultures. Furthermore, RSV supplementation promoted the polarization of the mitochondrial membrane in both cultures. Finally, RSV decreased the release of H2O2 with high-level glucose and increased it at low-level glucose. Altogether, this data supports the hypothesis that RSV supplementation decreases CLS as a result of mitochondrial dysfunction and this phenotype occurs in a glucose-dependent manner.

Energy-dependent effects of resveratrol in Saccharomyces cerevisiae.

The metabolic effects induced by resveratrol have been associated mainly with the consumption of high-calorie diets; however, its effects with standard or low-calorie diets remain unclear. To better understand the interactions between resveratrol and cellular energy levels, we used Saccharomyces cerevisiae as a model. Herein it is shown that resveratrol: (a) decreased cell viability in an energy-dependent manner; (b) lessening of cell viability occurred specifically when cells were under cellular respiration; and (c) inhibition of oxygen consumption in state 4 occurred at low and standard energy levels, whereas at high energy levels oxygen consumption was promoted. These findings indicate that the effects of resveratrol are dependent on the cellular energy status and linked to metabolic respiration. Importantly, our study also revealed that S. cerevisiae is a suitable and useful model to elucidate the molecular targets of resveratrol under different nutritional statuses. Copyright © 2016 John Wiley & Sons, Ltd.

Resveratrol increases glycolytic flux in Saccharomyces cerevisiae via a SNF1-dependet mechanism.

Evidence suggests that AMP protein kinase (AMPK) is the main target of the phytochemical resveratrol (RSV) in mammalian cells. Data also indicates that RSV stimulates glucose metabolism; however, the molecular link between RSV and glucose uptake remains unknown. Herein, we provide evidence indicating that RSV stimulates glycolysis via sucrose non-fermenting 1 gene (SNF1, Saccharomyces cerevisiae orthologous of AMPK). S. cerevisiae cultures treated with 30 µM RSV showed an increase in extracellular acidification rate compared to untreated cells, indicating an elevated glycolytic flux. Also, RSV treatment increased transcription levels of two key glycolytic genes, hexokinase 2 (HXK2) and phosphofructokinase 1 (PFK1), as well as production of NADH. Moreover, RSV treatment inhibited mitochondrial respiration when glucose was used as a carbon source. Importantly, the effects of RSV on glycolysis were dependent of SNF1. Taken together, these findings suggest that SNF1 (AMPK in mammalian systems) is the molecular target of RSV in S. cerevisiae.

Improving global influenza surveillance: trends of A(H5N1) virus in Africa and Asia.

BACKGROUND: Highly pathogenic avian influenza A(H5N1) viruses are an important health problem in many Asian and African countries. The current increase in human cases demonstrates that influenza A(H5N1) is still a significant global pandemic threat. Many health organizations have recognized the need for new strategies to improve influenza global surveillance. Specifically, the World Health Organization through the global technical consultation for influenza surveillance have called for a detailed picture of the current limitations, especially at the nation level, to evaluate, standardize and strength reporting systems. The main goal of our study is to demonstrate the value of genetic surveillance as part of a strategic surveillance plan. As a proof of concept, we evaluated the current situation of influenza A(H5N1) in Asian and Africa. RESULTS: Our analysis revealed a power-law distribution in the number of sequences of A(H5N1) viruses analyzed and/or reported to influenza surveillance networks. The majority of the Asian and African countries at great risk of A(H5N1) infections have very few (approximately three orders of magnitude) sequenced A(H5N1) viruses (e.g. hemagglutinin genes). This suggests that countries under pandemic alert for avian influenza A(H5N1) have very limited participation (e.g. data generation, genetic analysis and data share) in avian influenza A(H5N1) surveillance. More important, this study demonstrates the usefulness of influenza genetic surveillance to detect emerging pandemic threat viruses. CONCLUSIONS: Our study reveals that some countries suffering from human cases of avian influenza have limited participation (e.g. genetic surveillance or data share) with global surveillance networks. Also, we demonstrate that the implementation of genetic surveillance programs could increase and strengthen worldwide epidemic and pandemic preparedness. We hope that this work promotes new discussions between policy makers and health surveillance organizations to improve current methodologies and regulations.

Abundance and diversity of mucosa-associated hydrogenotrophic microbes in the healthy human colon.

Hydrogenotrophic microbiota have a significant impact on colonic health; however, little is known about their diversity and ecology in situ. Here, molecular-based methods and multivariate analyses were used to examine the abundance and diversity of mucosa-associated hydrogenotrophic microbes in 90 biopsies collected from right colon, left colon and rectum of 25 healthy subjects. Functional genes of all three hydrogenotrophic groups were detected in at least one colonic region of all subjects. Methanogenic archaea (MA) constituted approximately one half of the hydrogenotrophic microbiota in each colonic region. Sulfate-reducing bacteria (SRB) were more abundant than acetogens in right colon, while acetogens were more abundant than SRB in left colon and rectum. MA genotypes exhibited low diversity, whereas SRB genotypes were diverse and generally similar across the three regions within subject but significantly variable among subjects. Multivariate cluster analysis defined subject-specific patterns for the diversity of SRB genotypes; however, neither subject- nor region-specific clusters were observed for the abundance of hydrogenotrophic functional genes. Sequence analyses of functional gene clones revealed that mucosa-associated SRB were phylogenetically related to Desulfovibrio piger, Desulfovibrio desulfuricans and Bilophila wadsworthia; whereas MA were related to Methanobrevibacter spp., Mb. smithii and the order Methanomicrobiales. Together these data demonstrate for the first time that the human colonic mucosa is persistently colonized by all three groups of hydrogenotrophic microbes, which exhibit segmental and interindividual variation in abundance and diversity.

Lactobacillus probiotic protects intestinal epithelium from radiation injury in a TLR-2/cyclo-oxygenase-2-dependent manner.

BACKGROUND: The small intestinal epithelium is highly sensitive to radiation and is a major site of injury during radiation therapy and environmental overexposure. OBJECTIVE: To examine probiotic bacteria as potential radioprotective agents in the intestine. METHODS: 8-week-old C57BL/6 wild-type or knockout mice were administered probiotic by gavage for 3 days before 12 Gy whole body radiation. The intestine was evaluated for cell-positional apoptosis (6 h) and crypt survival (84 h). RESULTS: Gavage of 5×107 Lactobacillus rhamnosus GG (LGG) improved crypt survival about twofold (p<0.01); the effect was observed when administered before, but not after, radiation. Conditioned medium (CM) from LGG improved crypt survival (1.95-fold, p<0.01), and both LGG and LGG-CM reduced epithelial apoptosis particularly at the crypt base (33% to 18%, p<0.01). LGG was detected in the distal ileal contents after the gavage cycle, but did not lead to a detectable shift in bacterial family composition. The reduction in epithelial apoptosis and improved crypt survival offered by LGG was lost in MyD88⁻/⁻, TLR-2⁻/⁻ and cyclo-oxygenase-2⁻/⁻ (COX-2) mice but not TLR-4⁻/⁻ mice. LGG administration did not lead to increased jejunal COX-2 mRNA or prostaglandin E2 levels or a change in number of COX-2-expressing cells. However, a location shift was observed in constitutively COX-2-expressing cells of the lamina propria from the villi to a position near the crypt base (villi to crypt ratio 80:20 for control and 62:38 for LGG; p<0.001). Co-staining revealed these COX-2-expressing small intestinal lamina propria cells to be mesenchymal stem cells. CONCLUSIONS: LGG or its CM reduce radiation-induced epithelial injury and improve crypt survival. A TLR-2/MyD88 signalling mechanism leading to repositioning of constitutive COX-2-expressing mesenchymal stem cells to the crypt base is invoked.

Hydrogenotrophic microbiota distinguish native Africans from African and European Americans.

Reduced susceptibility to sporadic colorectal cancer in native Africans (NA) is correlated with low consumption of animal products and greater microbial production of colonic methane. In this context, two hydrogenotrophic microbial groups are of interest, methanogenic Archaea (MA) utilizing H2 to produce methane and sulfate-reducing bacteria (SRB) generating hydrogen sulfide, which has been linked with chronic inflammatory disorders of the colon. In the present study, stool samples from NA, consuming a diet high in resistant starch and low in animal products, and from African Americans (AA) and European Americans (EA), both consuming a typical Western diet, were examined for genetic diversity and structure of Archaea, MA and SRB communities. In general, a greater proportion of NA than AA and EA harboured the full range of targeted hydrogenotrophic groups. Terminal restriction fragment length polymorphism analysis of 16S rRNA genes and specific functional genes, combined with multivariate statistical analyses, revealed that NA harboured more diverse and different Archaea and MA populations than AA and EA. Also, NA harboured significantly distinct SRB populations compared with AA and EA. Taken together, these data are consistent with diet selecting for distinct hydrogenotrophic microbiota.

On the relationship between sialomucin and sulfomucin expression and hydrogenotrophic microbes in the human colonic mucosa.

The colonic mucus layer is comprised primarily of acidomucins, which provide viscous properties and can be broadly classified into sialomucins or sulfomucins based on the presence of terminating sialic acid or sulfate groups. Differences in acidomucin chemotypes have been observed in diseases such as colorectal cancer and inflammatory bowel disease, and variation in sialo- and sulfomucin content may influence microbial colonization. For example, sulfate derived from sulfomucin degradation may promote the colonization of sulfate-reducing bacteria (SRB), which through sulfate respiration generate the genotoxic gas hydrogen sulfide. Here, paired biopsies from right colon, left colon, and rectum of 20 subjects undergoing routine screening colonoscopies were collected to enable parallel histochemical and microbiological studies. Goblet cell sialo- and sulfomucins in each biopsy were distinguished histochemically and quantified. Quantitative PCR and multivariate analyses were used to examine the abundance of hydrogenotrophic microbial groups and SRB genera relative to acidomucin profiles. Regional variation was observed in sialomucins and sulfomucins with the greatest abundance of each found in the rectum. Mucin composition did not appear to influence the abundance of SRB or other hydrogenotrophic microbiota but correlated with the composition of different SRB genera. A higher sulfomucin proportion correlated with higher quantities of Desulfobacter, Desulfobulbus and Desulfotomaculum, relative to the predominant Desulfovibrio genus. Thus, acidomucin composition may influence bacterial sulfate respiration in the human colon, which may in turn impact mucosal homeostasis. These results stress the need to consider mucus characteristics in the context of studies of the microbiome that target intestinal diseases.