International audience | Trichothecenes (TCT) are very common mycotoxins. While the effects of DON, the most prevalent TCT, have been extensively studied, less is known about the effect of other trichothecenes. DON has ribotoxic, pro-inflammatory, and cytotoxic potential and induces multiple toxic effects in humans and animals. Although DON is not genotoxic by itself, it has recently been shown that this toxin exacerbates the genotoxicity induced by model or bacterial genotoxins. Here, we show that five TCT, namely T-2 toxin (T-2), diacetoxyscirpenol (DAS), nivalenol (NIV), fusarenon-X (FX), and the newly discovered NX toxin, also exacerbate the DNA damage inflicted by various genotoxins. The exacerbation was dose dependent and observed with phleomycin, a model genotoxin, captan, a pesticide with genotoxic potential, and colibactin, a bacterial genotoxin produced by the intestinal microbiota. For this newly described effect, the trichothecenes ranked in the following order: T-2>DAS > FX > NIV ≥ DON ≥ NX. The genotoxic exacerbating effect of TCT correlated with their ribotoxic potential, as measured by the inhibition of protein synthesis. In conclusion, our data demonstrate that TCT, which are not genotoxic by themselves, exacerbate DNA damage induced by various genotoxins. Therefore, foodborne TCT could enhance the carcinogenic potential of genotoxins present in the diet or produced by intestinal bacteria.

International audience | Trichothecenes (TCT) are very common mycotoxins. While the effects of DON, the most prevalent TCT, have been extensively studied, less is known about the effect of other trichothecenes. DON has ribotoxic, pro-inflammatory, and cytotoxic potential and induces multiple toxic effects in humans and animals. Although DON is not genotoxic by itself, it has recently been shown that this toxin exacerbates the genotoxicity induced by model or bacterial genotoxins. Here, we show that five TCT, namely T-2 toxin (T-2), diacetoxyscirpenol (DAS), nivalenol (NIV), fusarenon-X (FX), and the newly discovered NX toxin, also exacerbate the DNA damage inflicted by various genotoxins. The exacerbation was dose dependent and observed with phleomycin, a model genotoxin, captan, a pesticide with genotoxic potential, and colibactin, a bacterial genotoxin produced by the intestinal microbiota. For this newly described effect, the trichothecenes ranked in the following order: T-2>DAS > FX > NIV ≥ DON ≥ NX. The genotoxic exacerbating effect of TCT correlated with their ribotoxic potential, as measured by the inhibition of protein synthesis. In conclusion, our data demonstrate that TCT, which are not genotoxic by themselves, exacerbate DNA damage induced by various genotoxins. Therefore, foodborne TCT could enhance the carcinogenic potential of genotoxins present in the diet or produced by intestinal bacteria.

With the rapid development of nanotechnology in agriculture, there is increasing urgency to assess the impacts of nanoparticles (NPs) on the soil environment. This study merged raw high-throughput sequencing (HTS) data sets generated from 365 soil samples to reveal the potential ecological effects of NPs on soil microbial community by means of metadata analysis and machine learning methods. Metadata analysis showed that treatment with nanoparticles did not have a significant impact on the alpha diversity of the microbial community, but significantly altered the beta diversity. Unfortunately, the abundance of several beneficial bacteria, such as Dyella, Methylophilus, Streptomyces, which promote the growth of plants, and improve pathogenic resistance, was reduced under the addition of synthetic nanoparticles. Furthermore, metadata demonstrated that nanoparticles treatment weakened the biosynthesis ability of cofactors, carriers, and vitamins, and enhanced the degradation ability of aromatic compounds, amino acids, etc. This is unfavorable for the performance of soil functions. Besides the soil heterogeneity, machine learning uncovered that a) the exposure time of nanoparticles was the most important factor to reshape the soil microbial community, and b) long-term exposure decreased the diversity of microbial community and the abundance of beneficial bacteria. This study is the first to use a machine learning model and metadata analysis to investigate the relationship between the properties of nanoparticles and the hazards to the soil microbial community from a macro perspective. This guides the rational use of nanoparticles for which the impacts on soil microbiota are minimized.

The homeostasis of gut immunity and microbiota are associated with the health of the gut. Dechlorane 602 (Dec 602) with food web magnification potential has been detected in daily food. People who were orally exposed to Dec 602 may encounter increased risk of health problems in the gut. In order to reveal the influence of short-term exposure of Dec 602 on gut immunity and microbiota, adult female C57BL/6 mice were administered orally with Dec 602 (low/high doses: 1.0/10.0 μg/kg body weight per day) for 7 days. Lymphocytes were examined by flow cytometry. Gut microbiota was measured by 16S rRNA gene sequencing. Results showed that fecal IgA was upregulated after exposure to the high dose of Dec 602, suggesting that there might be inflammation in the gut. Then, changes of immune cells in mesenteric lymph nodes and colonic lamina propria were examined. We found that exposure to the high dose of Dec 602 decreased the percentages of the anti-inflammatory T regulatory cells in mesenteric lymph nodes. In colonic lamina propria, the production of gut protective cytokine interleukin-22 by CD4⁺ T cells was decreased, and a decreased trend of interleukin-22 production was also observed in type 3 innate lymphoid cells in the high dose group. Furthermore, an altered microbiota composition toward inflammation in the gut was observed after exposure to Dec 602. Additionally, the altered microbiota correlated with changes of immune parameters, suggesting that there were interactions between influenced microbiota and immune parameters after exposure to Dec 602. Taken together, short-term exposure to Dec 602 induced gut immunity and microbiota perturbations, and this might be the mechanisms for Dec 602 to elicit inflammation in the gut.

The gut microbiota is important for maintaining homeostasis of the host. Gut microbes represent the initial site for toxicant processing following dietary exposures to environmental contaminants. The diet is the primary route of exposure to polychlorinated biphenyls (PCBs), which are absorbed via the gut, and subsequently interfere with neurodevelopment and behavior. Developmental exposures to PCBs have been linked to increased risk of neurodevelopmental disorders (NDD), including autism spectrum disorder (ASD), which are also associated with a high prevalence of gastrointestinal (GI) distress and intestinal dysbiosis. We hypothesized that developmental PCB exposure impacts colonization of the gut microbiota, resulting in GI pathophysiology, in a genetically susceptible host. Mouse dams expressing two heritable human mutations (double mutants [DM]) that result in abnormal Ca²⁺ dynamics and produce behavioral deficits (gain of function mutation in the ryanodine receptor 1 [T4826I-RYR1] and a human CGG repeat expansion [170–200 CGG repeats] in the fragile X mental retardation gene 1 [FMR1 premutation]). DM and congenic wild type (WT) controls were exposed to PCBs (0–6 mg/kg/d) in the diet starting 2 weeks before gestation and continuing through postnatal day 21 (P21). Intestinal physiology (Ussing chambers), inflammation (qPCR) and gut microbiome (16S sequencing) studies were performed in offspring mice (P28–P30). Developmental exposure to PCBs in the maternal diet caused significant mucosal barrier defects in ileum and colon (increased secretory state and tight junction permeability) of juvenile DM mice. Furthermore, PCB exposure increased the intestinal inflammatory profile (Il6, Il1β, and Il22), and resulted in dysbiosis of the gut microbiota, including altered β-diversity, in juvenile DM mice developmentally exposed to 1 mg/kg/d PCBs when compared to WT controls. Collectively, these findings demonstrate a novel interaction between PCB exposure and the gut microbiota in a genetically susceptible host that provide novel insight into environmental risk factors for neurodevelopmental disorders.

Concerns regarding microplastic contamination have spread from aquatic environments to terrestrial systems with a growing number of studies have been reported. Notwithstanding, the potential effects on soil ecosystems remain largely unexplored. In this study, the effects of polyethylene microplastics on soil enzymatic activities and the bacterial community were evaluated, and the microbiota colonizing on microplastics were also investigated. Microplastic amendment (2000 fragments per kg soil) significantly increased the urease and catalase activities in soil after 15 days, and no discernible alteration of invertase activities was detected. Results from high-throughput sequencing of 16S rRNA revealed that the alpha diversities (richness, evenness, and diversity) of the microbiota in soil were not obviously changed by the PE amendment, whereas the diversity indexes of microbiota on plastic fragments were significantly lower than those in the control and amended soils. Different taxonomic composition was observed in between the control and amended soils after 90 days of incubation. Bacterial assemblages with distinct community structure colonized the PE microplastics. Additionally, several taxa including plastic-degrading bacteria and pathogens were more abundant on microplastics. Simultaneously, the predicted functional profiles showed that the pathways of amino acid metabolism and xenobiotics biodegradation and metabolism were higher on the microplastics. These results indicated that microplastics in soil, compared with those in aquatic environments, can also act as a distinct microbial habitat, potentially altering the ecological functions of soil ecosystems.

Recently, concerns have been raised that residues of glyphosate-based herbicides may interfere with the homeostasis of the intestinal bacterial community and thereby affect the health of humans or animals. The biochemical pathway for aromatic amino acid synthesis (Shikimate pathway), which is specifically inhibited by glyphosate, is shared by plants and numerous bacterial species. Several in vitro studies have shown that various groups of intestinal bacteria may be differently affected by glyphosate. Here, we present results from an animal exposure trial combining deep 16S rRNA gene sequencing of the bacterial community with liquid chromatography mass spectrometry (LC-MS) based metabolic profiling of aromatic amino acids and their downstream metabolites. We found that glyphosate as well as the commercial formulation Glyfonova®450 PLUS administered at up to fifty times the established European Acceptable Daily Intake (ADI = 0.5 mg/kg body weight) had very limited effects on bacterial community composition in Sprague Dawley rats during a two-week exposure trial. The effect of glyphosate on prototrophic bacterial growth was highly dependent on the availability of aromatic amino acids, suggesting that the observed limited effect on bacterial composition was due to the presence of sufficient amounts of aromatic amino acids in the intestinal environment. A strong correlation was observed between intestinal concentrations of glyphosate and intestinal pH, which may partly be explained by an observed reduction in acetic acid produced by the gut bacteria. We conclude that sufficient intestinal levels of aromatic amino acids provided by the diet alleviates the need for bacterial synthesis of aromatic amino acids and thus prevents an antimicrobial effect of glyphosate in vivo. It is however possible that the situation is different in cases of human malnutrition or in production animals.

Recent studies have indicated that Galleria mellonella larvae ingest polyethylene films and the degradation mechanism could inspire biotechnological exploitation for degrading plastic to eliminate global pollution from plastic waste. In this study, we tested the chemical compositions of masticated and ingested different plastic types by G. mellonella. High throughput sequencing of 16S rRNA gene was used to characterize the alteration of the microbial communities derived from salivary glands, gut contents and whole G. mellonella larvae. Our results indicated that G. mellonella is able to masticate polyethylene (PE), expanded polystyrene (EPS) and polypropylene (PP) and convert it to small particles with very large and chemically modified surfaces. The characteristics of the polymer affect the rate of damage. Formation of functional carbonyl groups on the appearance of oxidized metabolic intermediates of polyolefins in the frass samples observed. We found that the mastication of EPS, PP or PE could significantly alter the microbial composition in the gut content while it did not appear to influence the salivary glands microbial community. Representatives of Desulfovibrio vulgaris and Enterobacter grew with the PE diet while mastication of polystyrene and polypropylene increased the abundance of Enterococcus. The evaluation of bacterial communities in whole larvae confirmed the obtained result and additionally showed that the abundance of Paenibacillus, Corynebacterium and Commamonadaceae increased by Styrofoam (EPS) consumption.

Xenobiotics are worldwide distributed and humans are unavoidably exposed to multiple chemical compounds during life, from preconception to adulthood. The human microbiota is mainly settled during early life and modulate host health and fitness. One of the main routes for chemical exposure is by intake of contaminated food and water. Thus, the interplay between diet-xenobiotics-microbiota during pregnancy and perinatal period may have relevant consequences for infant and adult health. Maternal exposure to metal(oid)s, persistent organic pollutants, and some food additives can modify the infant’s microbiota with unknown consequences for child or adult health. Toxicants’ exposure may also modulate the maternal transfer of microorganisms to the progeny during birth and breastfeeding; however, scarce information is available. The rapid increase in releasing novel chemicals to the environment, the exposure to chemical mixtures, the chronic/low dose scenario, and the delay in science-stakeholders action call for novel and groundbreaking approaches to improve a comprehensive risk assessment in sensitive population groups like pregnant women and neonates, with emphasis on microbiota as modulating factor and target-organ of xenobiotic’s toxicity.

Glyphosate is the most popular herbicide used worldwide. This study aimed to investigate the adverse effects of glyphosate on the small intestine and gut microbiota in rats. The rats were gavaged with 0, 5, 50, and 500 mg/kg of body weight glyphosate for 35 continuous days. The different segments of the small intestine were sampled to measure indicators of oxidative stress, ion concentrations and inflammatory responses, and fresh feces were collected for microbiota analysis. The results showed that glyphosate exposure decreased the ratio of villus height to crypt depth in the duodenum and jejunum. Decreased activity of antioxidant enzymes (T-SOD, GSH, GSH-Px) and elevated MDA content were observed in different segments of the small intestine. Furthermore, the concentrations of Fe, Cu, Zn and Mg were significantly decreased or increased. In addition, the mRNA expression levels of IL-1β, IL-6, TNF-α, MAPK3, NF-κB, and Caspase-3 were increased after glyphosate exposure. The 16 S rRNA gene sequencing results indicated that glyphosate exposure significantly increased α-diversity and altered bacterial composition. Glyphosate exposure significantly decreased the relative abundance of the phylum Firmicutes and the genus Lactobacillus, but several potentially pathogenic bacteria were enriched. In conclusion, this study provides important insight to reveal the negative influence of glyphosate exposure on the small intestine, and the altered microbial composition may play a vital role in the process.