Effects of short-term continuous and pulse cadmium exposure on gut histology and microbiota of adult male frogs (Pelophylax nigromaculatus) during pre-hibernation

Diverse Perspectives Illuminate the Intestinal Toxicity of Traditional and Biodegradable Agricultural Film Microplastics to Eisenia fetida under Varying Exposure Sequences

The widespread use of plastic agricultural films necessitates a thorough evaluation of environmental risks posed by soil microplastics (MPs). While the intestinal tract is a critical site for MP interactions in soil organisms, current research predominantly focuses on overall physiological responses, overlooking organ-specific toxic mechanisms. To address this gap, we exposed earthworms (Eisenia fetida) to polyethylene (PE) and biodegradable polylactic acid (PLA) MPs sourced from agricultural films at an environmentally realistic concentration of 1.0 g/kg. Incorporating natural earthworm mobility, we designed two exposure scenarios: migration from clean to contaminated soil (scenario A) and vice versa (scenario B). Machine learning-driven image analysis and phenotypic profiling revealed that PE induced more severe intestinal lesions than PLA, adversely affecting intestinal immune functions. Furthermore, PE resulted in greater oxidative damage and significantly activated immune proteins such as melanin and antimicrobial peptides through reprograming immune-related gene and protein pathways. Conversely, PLA predominantly disrupted intestinal digestive and absorptive functions, though the gut microbial community partially mitigated damage through structural and compositional adaptation. Compared with scenario A, earthworms in scenario B exhibited reduced tissue damage, enhanced digestive enzyme activity, and upregulated energy-related metabolites and cell proliferation genes, indicating partial recovery from MP-induced intestinal dysfunction. These findings elucidate the distinct toxicity mechanisms of conventional and biodegradable agricultural MPs on soil organisms, while the scenario-based approach advances risk assessment by aligning experimental design with real-world ecological behaviors.

The influences of pulse exposure versus continuous exposure to cadmium are different: Mechanisms elucidated from motor behavior and brain in amphibian larvae

Cadmium (Cd) is a common environmental pollutant in aquatic ecosystems, often present in the form of pulses. However, the toxic effects of Cd on aquatic animals have been found to come primarily from continuous exposure, and there is little research on the effects of pulse exposure on animals. Here, the different effects of Cd exposure patterns on the motor behavior, brain histology and brain metabolism of Pelophylax nigromaculatus tadpoles (20 per parallel group) were explored. Our study showed that both continuous (CECd) and pulse exposure of Cd (PECd) led to a significant reduction in the moving distance (57.7 % vs 42.5 %), average speed (57.7 % vs 42.6 %) and moving frequency (45.3 % vs 7.9 %). Furthermore, both CECd and PECd led to the expansion and enlargement of the perivascular space of the cerebrum. Cd exposure increased the blood-brain barrier permeability, leading to brain cell swelling, and destroyed brain granular cells, Purkinje cells and brain gliacytes. Non-targeted metabolomics found a significant effect of Cd exposure on nucleic acid and amino acid metabolism. The most significant increases were observed in adenosine (99.4 %), threonine (47.9 %), citrulline (123.9 %), and erythrose 4p (184.1 %). It is noteworthy that the CECd exerted a more pronounced influence on brain structure, metabolism, and movement behaviour than the PECd. This phenomenon can be attributed to the fact that in PECd exposure, the individual's intermittent exposure to clean water partially offsets the effects of previous Cd exposure.

The gut microbiota: A key player in cadmium toxicity - implications for disease, interventions, and combined toxicant exposures

Cadmium (Cd) is a highly toxic heavy metal contaminant found in soil and water due to human activities such as mining and industrial discharge. Cd can accumulate in the body, leading to various health risks such as organ injuries, osteoporosis, renal dysfunction, Type 2 diabetes (T2DM), reproductive diseases, hypertension, cardiovascular diseases, and cancers. The gut is particularly sensitive to Cd toxicity as it acts as the primary barrier against orally ingested Cd. Even at low concentrations, Cd can cause oxidative stress, inflammation, and intestinal bleeding. Cd also disrupts the gut microbiota, affecting its structure, taxonomic composition, and metabolic functions. Cd exposure alters the structure of the gut microbial community, reducing diversity and upregulating certain phyla and genera. This disturbance can lead to physiological and metabolic imbalances, including disruptions in energy homeostasis, amino acid, lipid, nucleotide, and short-chain fatty acid (SCFAs) metabolism. The effects of Cd on the gut microbiota depend on the duration of exposure, the dose of Cd, and can vary based on sex and age. Cd-induced gut dysbiosis has been linked to various diseases, including diabetes, adiposity, atherosclerosis, liver damage, infections, cancer, and neurodegenerative diseases. Interventions targeting the gut microbiota, such as probiotics, specific diets, melatonin, selenium, vitamin D3, and certain compounds, have shown potential in reducing the health risks associated with Cd exposure. However, combined exposure to Cd and other toxicants, such as microplastics (MPs), heavy metals, and antibiotics, can amplify the toxicity and dysbiosis in the gut microbiota.

Synergistic toxicity of cadmium and triadimefon on the microbiota and health of Rana dybowskii tadpoles

The skin and gut microbiota are crucial to amphibians. Triadimefon (TF), a widely used triazole fungicide, controls crop diseases and regulates growth, with uncertain effects on amphibian microbiota. Contamination, typically involving mixed chemicals at low concentrations, including cadmium (Cd) and TF, may detrimentally affect amphibian growth, survival, and microbiota health in both the skin and gut, but few research has examined these consequences. This research examines the impact of Cd and TF on Rana dybowskii tadpoles, focusing on survival, body mass, and microbiome changes over 28 days across four groups: control, Cd, TF, and Cd + TF groups. Results showed significant reductions in survival and body mass in Cd and TF-treated groups, with the combination group being the most affected. Microbiota analysis revealed significant dysbiosis in both gut and skin microbiomes under pollutant stress, with a marked microbiota and a shift in dominant microbial communities. Function prediction analysis based on the microbiome composition highlighted significant differences across various biological pathways, including metabolism, immune system, environmental adaptation, and disease resistance. These alterations suggest that pollutant exposure compromises the tadpoles' ability to maintain homeostasis and resist pathogens. In conclusion, this study reveals the detrimental effects of Cd and TF on the survival, growth, and microbiomes of R. dybowskii tadpoles, indicating significant environmental and health risks.

Low molecular weight galactomannan alleviates diarrhea induced by senna leaf in mice via intestinal barrier improvement and gut microbiota modulation

Low molecular weight galactomannan (LMGM), a soluble dietary fibre derived from guar gum, is recognized for its prebiotic functions, including promoting the growth of beneficial intestinal bacteria and the production of short-chain fatty acids, but the mechanism of alleviating diarrhea is not fully understood. This study established an acute diarrhea mouse model using senna leaf decoction and evaluated the therapeutic effects of LMGM by monitoring diarrhea scores, loose stool prevalence, intestinal tissue pathology and gene expression, and gut microbiota composition and metabolisms. The results indicated that LMGM significantly reduced diarrhea scores and loose stool prevalence within two hours post-treatment. Hematoxylin and eosin staining and quantitative real-time polymerase chain reaction analysis revealed that LMGM improved intestinal epithelial structure and up-regulated the expression of zonula occludens 1, occludin, mucin 2, aquaporin 3, and aquaporin 4 in ileum, jejunum, and colon tissues. Moreover, LMGM increased the abundance of beneficial bacteria such as Lactobacillaceae and Lachnospiraceae, and decreased Prevotellaceae in the cecum. Furthermore, LMGM promoted short-chain fatty acid production and reduced ammonia nitrogen and skatole concentrations in the intestinal content. The study suggests that LMGM could serve as a functional prebiotic for diarrhea alleviation, potentially by enhancing the intestinal barrier, modulating water transportation, and regulating the microbiota composition.

Effects of cadmium exposure on gut microbiota and antibiotic resistance genes in Haliotis diversicolor abalone

Heavy metals in soil, water, and industrial production can affect the antibiotic resistance of bacteria. Antibiotic resistance in gut microbiota has been extensively researched. The effects of cadmium (Cd) was investigated on the gut microbiota and antibiotic resistance genes (ARGs) of Haliotis diversicolor, a commercially important abalone species. By exposing H. diversicolor to four concentrations of Cd (0 μg L-1 (control), 6.5 μg L-1 (low), 42.25 μg L-1 (medium), and 274.63 μg L-1 (high)) for 30 and 60 days, 16 types of ARG (aadA-01, aadA-02, cfr, dfrA1, ermB, floR, folA, mecA, sul2, tetB-01, tetC-01, tetD-01, tetG-01, tetM-02, tetQ, vanC-01), and 1213 genus and 27 phylum microbiomes were detected. ARGs can be resistant to aminoglycoside, beta-lactamase, macrolide-lincosamide-streptogramin B, multidrug, florfenicol, macrolide, sulfonamides, tetracyclines, and vancomycin. Cadmium exposure significantly alters the abundance of tetC-01, tetB-01, tetQ, sul2, and aadA-01. About 5% (61) of genus-level microorganisms were significantly affected by Cd exposure. Microbiota alpha and beta diversities in the 60-day 42.25 μg L-1 Cd treatment differed significantly from those in other treatments. In addition, 26 pathogens were detected, and two pathogens (Vibrio and Legionella) were significantly affected by Cd exposure. Significant correlations between pathogens and ARGs increased with increased Cd concentration after 60 days of Cd exposure. Cadmium exposure may cause gut microbiota disturbance in H. diversicolor and increase the likelihood of ARG transfer to pathogens, increasing potential ecological and economic risks.

Influences of continuous and pulse atrazine exposure on intestinal flora and metabolites of Pelophylax nigromaculatus tadpoles

Atrazine, a widely used herbicide, has adverse effects on the growth and metabolism of amphibians. Due to the cyclical application use of the pesticide atrazine in agricultural production, atrazine concentrations in water occur in the form of pulses. However, knowledge of the effects of atrazine pulse exposure on the gut microbiota and metabolism of amphibians is limited. In this study, Pelophylax nigromaculatus tadpoles (Gs 26) were exposed to continuous and pulse atrazine (100 μg/L) for 60 days. The results showed that continuous exposure and pulse exposure had different effects on the diversity of gut microbiota. At the phyla level, pulse exposure significantly increased the relative abundance of Actinobacteria, and decreased the relative abundance of Firmicutes compared to continuous exposure. At the genus level, continuous and pulse exposure to atrazine significantly altered the relative abundance of Acetobacterium, Microbacterium, Bacteroides, Eulopiscium and Leuconostoc. Compared to continuous exposure, pulse exposure significantly increased the relative abundance of Microbacterium, and significantly decreased the relative abundance of Acetobacterium and Eplopiscium. In terms of metabolism, pulse exposure significantly increased the relative abundance of creatine, guanine, and inosine and significantly decreased the relative abundance of 3-hydroxysebacic acid, ganoderic acid F, hypoxanthine, and withaperuvin H compared to continuous exposure. Continuous and pulse exposure to atrazine significantly altered the relative abundance of metabolites of the pymidine metabolism, purine metabolism, beta-alanine metabolism and other pathways in the gut of P. nigromaculatus tadpoles. In addition, changes in most metabolites had a significant correlation with changes in gut microorganisms. In conclusion, our study confirmed that pulse exposure to atrazine has a greater effect on the composition of the gut microflora and the metabolism of P. nigromaculatus tadpoles than continuous exposure.

Protective Effects of Bacteriocin-Producing Lactiplantibacillus plantarum on Intestinal Barrier of Mice

Bacteriocins are crucial metabolites of probiotics that display beneficial functions. The intestinal barrier is an important target on which probiotics exert their intestinal health activity. However, the impacts of bacteriocin-producing probiotics on the intestinal barrier are unclear. In this study, the effects of bacteriocin-producing Lactiplantibacillus plantarum Q7 and L. plantarum F3-2 on the intestinal barrier of mice were explored. It was shown that L. plantarum Q7 promoted the expression of mucin MUC2 to enhance the protection provided by the intestinal mucus layer. L. plantarum Q7 up-regulated the gene expression of intestinal tight junction proteins ZO-1 and JAM-1 significantly, and L. plantarum F3-2 up-regulated ZO-1 and Claudin-1 markedly, which exhibited tight junction intestinal barrier function. The two strains promoted the release of IgA and IgG at varying degrees. The antimicrobial peptide gene RegIIIγ was up-regulated markedly, and the gene expression of inflammatory cytokines appeared to exhibit an upward trend with L. plantarum Q7 treatment, so as to enhance intestinal immune regulation function. Furthermore, L. plantarum Q7 and L. plantarum F3-2 increased the abundance of the beneficial bacteria Muribaculaceae, inhibited the growth of the harmful bacteria Parabacteroides, and facilitated the synthesis of total short-chain fatty acids (SCFAs), which seemed to favor the prevention of metabolic diseases. Our results suggested that L. plantarum Q7 and L. plantarum F3-2 showed strain specificity in their protective effects on the intestinal chemical, physical, immunological and biological barriers of mice, which provided theoretical support for the selective utilization of bacteriocin-producing strains to regulate host health.

Encouraging news for in situ conservation: Translocation of salamander larvae has limited impacts on their skin microbiota

The key role of symbiotic skin bacteria communities in amphibian resistance to emerging pathogens is well recognized, but factors leading to their dysbiosis are not fully understood. In particular, the potential effects of population translocations on the composition and diversity of hosts' skin microbiota have received little attention, although such transfers are widely carried out as a strategy for amphibian conservation. To characterize the potential reorganization of the microbiota over such a sudden environmental change, we conducted a common-garden experiment simulating reciprocal translocations of yellow-spotted salamander larvae across three lakes. We sequenced skin microbiota samples collected before and 15 days after the transfer. Using a database of antifungal isolates, we identified symbionts with known function against the pathogen Batrachochytrium dendrobatidis, a major driver of amphibian declines. Our results indicate an important reorganization of bacterial assemblages throughout ontogeny, with strong changes in composition, diversity and structure of the skin microbiota in both control and translocated individuals over the 15 days of monitoring. Unexpectedly, the diversity and community structure of the microbiota were not significantly affected by the translocation event, thus suggesting a strong resilience of skin bacterial communities to environmental change-at least across the time-window studied here. A few phylotypes were more abundant in the microbiota of translocated larvae, but no differences were found among pathogen-inhibiting symbionts. Taken together, our results support amphibian translocations as a promising strategy for this endangered animal class, with limited impact on their skin microbiota.