Probiotic supplementation mitigates the developmental toxicity of perfluorobutanesulfonate in zebrafish larvae

Effect of Bacillus velezensis MT9 on Nile Tilapia (Oreochromis Niloticus) Intestinal Microbiota

In recent years, there has been a growing interest in the use of probiotics in aquaculture, due to their effectiveness on production, safety, and environmental friendliness. Probiotics, used as feed additives and as an alternative to antibiotics for disease prevention, have been shown to be active as growth promoters, improving survival and health of farmed fish. In this study, we have investigated the ability of the strain Bacillus velezensis MT9, as potential probiotic, to modulate the intestinal microbiota of the Nile tilapia (Oreochromis niloticus) fed with the Bacillus velezensis-supplemented feed in an experimental aquaculture plant. The analysis of the microbial community of the Nile tilapia by culture-based and 16S rRNA gene metabarcoding approaches demonstrated that B. velezensis MT9 reshapes the fish intestinal microbiota by reducing the amounts of opportunistic Gram-negative bacterial pathogens belonging to the phylum of Proteobacterium (Pseudomonadota) and increasing the amounts of beneficial bacteria belonging to the phyla Firmicutes (Bacillota) and Actinobacteria (Actinomycetota). Specifically, dietary supplementation of Nile tilapia with B. velezensis MT9 resulted in an increase in the relative abundance of bacteria of the genus Romboutsia, which has a well-documented probiotic activity, and a decrease in the relative abundance of Gammaproteobacteria of the genera Aeromonas and Vibrio, which include opportunistic pathogens for fish, and Escherichia/Shigella, which may pose a risk to consumers. The whole genome sequence of B. velezensis MT9 was then determined. Genome analysis revealed several peculiarities of B. velezensis MT9 compared to other B. velezensis reference strains including specific metabolic traits, differences in two-component and quorum sensing systems as well as the potential ability to produce a distinct array of secondary metabolites, which could explain the strong ability of this strain to modulate the intestinal microbiota of the Nile tilapia.

Mitigation of PFOA-Induced Developmental Toxicity in Danio rerio by Bacillus subtilis var. natto: Focus on Growth and Ossification

Perfluorooctanoic acid (PFOA) is a persistent environmental contaminant that resists biological degradation and accumulates in organisms. It disrupts zebrafish embryo development, affecting their heartbeat rate and locomotion. Meanwhile, probiotics are known to enhance the development and ossification of zebrafish embryos. In this study, we examined the toxic effects of PFOA on growth and bone formation in zebrafish and the potential of the probiotic Bacillus subtilis var. natto to counteract its toxicity. Larvae were exposed to 0, 50, or 100 mg/L PFOA from hatching to 21 days post-fertilization (dpf), with or without dietary probiotic supplementation (107 CFU/larva/day), and they were sampled at 7, 14, and 21 dpf. PFOA exposure reduced standard length at 21 dpf, while the co-administration of probiotics mitigated these effects. Craniofacial cartilage defects appeared in larvae exposed to 50 mg/L PFOA at 7 and 14 dpf, while 100 mg/L PFOA impaired bone development at 7 dpf. Probiotics counteracted these abnormalities. PFOA also delayed ossification, correlating with the downregulation of col10a1a, runx2b, and cyp26b1, while the probiotic treatment restored normal ossification. These findings improve our understanding of PFOA's detrimental effects on zebrafish growth and bone formation while demonstrating the protective role of probiotics against PFOA-induced developmental toxicity.

Lactiplantibacillus plantarum N1 derived lipoteichoic acid alleviates insulin resistance in association with modulation of the gut microbiota and amino acid metabolism

This study aimed to investigate the effects of heat-killed Lactiplantibacillus plantarum N1 (HK-N1) and lipoteichoic acid (LTA) derived from it on alleviating insulin resistance by modulating the gut microbiota and amino acid metabolism. High-fat diet (HFD)-fed mice were administered live bacteria or HK-N1, and the results demonstrated that HK-N1 significantly reduced epididymal adipocyte size and serum low density lipoprotein-cholesterol, and improved insulin resistance by increasing the YY peptide and glucagon-like peptide levels. HK-N1 also modulated the gut microbiome composition, enhancing microbiota uniformity and reducing the abundance of Ruminococcus, Oscillospira and norank_f_Mogibacteriaceae. Three main active substances obtained from HK-N1 (membrane protein, peptidoglycan, and lipoteichoic acid) were also used to investigate their potential effects in hyperglycemic zebrafish. Only LTA reduced blood sugar and altered the gut microbiome, particularly reducing Aeromonas, which is positively related to hyperglycemia. Untargeted metabolomics revealed that LTA improved vitamin and amino acid metabolism, thereby alleviating metabolic disorders in zebrafish. Collectively, our findings indicate that HK-N1, primarily through LTA, modulated insulin sensitivity by regulating the gut microbiota and amino acid metabolism, offering a potential therapeutic strategy for insulin resistance and type 2 diabetes mellitus.

Interaction between young fecal transplantation and perfluorobutanesulfonate endocrine disrupting toxicity in aged recipients: An estrobolome perspective

Transplanting young feces into the aged was found to effectively counteract the endocrine disrupting effects of perfluorobutanesulfonate (PFBS) pollutant, showing promise in the maintenance of healthy aging. However, the interactive mechanisms between young fecal transplantation and PFBS endocrine disruption during aging remain unclear. In this follow-up study, aged zebrafish were administered young donor feces and then exposed to environmentally relevant concentrations of PFBS (0 and 100 μg/L). Alterations in the holistic estrobolome along gut-liver axis were investigated. The results showed that PFBS singular exposure significantly increased blood estradiol concentration in the aged, inducing an estrogenic activity. Concentrations of other estrogen forms, including estrone and estriol, were also disrupted by PFBS. Interestingly, young fecal transplant effectively mitigated the estrogenic toxicity of PFBS and largely restored estrogen equilibrium. After PFBS exposure, the transcriptions of estrogen metabolic genes were consistently upregulated in aged livers, causing the accumulation of 2-methoxyestradiol-3-methylether metabolite. In contrast, aged livers coexposed to young fecal transplant and PFBS enhanced the glucuronidation process, successfully facilitating the elimination and detoxification of estrogen metabolites. In aged gut, PFBS exposure inhibited β-glucuronidase enzyme activity, implying the suppression of estrogen deconjugation and recycle. However, in the combined group, β-glucuronidase activity was significantly stimulated, thus reestablishing estrobolome dynamics. Overall, current findings provide mechanistic insights into the antagonistic interaction between young fecal transplant and PFBS on reproductive endocrinology. Gut microbiota manipulation appears appealing to maintain healthy aging progression albeit the interruption of environmental xenobiotics.

Cytotoxicity and mechanisms of perfluorobutane sulfonate (PFBS) in umbilical cord fibroblast cells of Yangtze finless porpoise

Yangtze finless porpoises (YFP) accumulate high levels of per- and polyfluoroalkyl substances (PFASs). However, the health impacts of PFASs to YFP are still unknown because it is technically and ethically unfeasible to use the critically endangered YFP in toxicological exposures. To uncover the potential toxicities of PFASs to YFP, this study exposed a YFP umbilical cord fibroblast cell line to perfluorobutane sulfonate (PFBS), an emerging PFASs pollutant in the aquatic environments. After exposure, the cytotoxicity and mechanisms of PFBS were explored. Our preliminary experiments found that PFBS compromised the cell viability in a concentration and duration dependent manner. In an exposure of 48-h duration, the maximum no observed effect concentration (NOEC) of PFBS was determined to be 400 µM. High-throughput proteomics were then conducted to identify the differentially expressed proteins in YFP cells exposed to 400 µM PFBS for 48 h. The results found that PFBS exposure significantly perturbed the proteome fingerprints of YFP umbilical cord fibroblast cells. Functional annotation of differential proteins showed that PFBS had the potential to impair a variety of biological processes associated with the immunity, oxidative stress, metabolism, and proteolysis. Consistently, the intracellular levels of reactive oxygen species (ROS) and proinflammatory cytokine IL-1β were significantly increased by PFBS in YFP umbilical cord fibroblast cells. Overall, this study highlights the toxic effects of emerging PFASs on YFP and provides reference data to evaluate the health risks of aquatic pollution under the context of national YFP protection. To our knowledge, this is the first omics study using YFP umbilical cord fibroblast cells in ecotoxicology of PFASs, which is applicable to various cetacean species and pollutants.

Probiotics Alleviate Microcystin-LR-Induced Developmental Toxicity in Zebrafish Larvae

Microcystin-LR (MCLR) poses a significant threat to aquatic ecosystems and public health. This study investigated the protective effects of the probiotic Lactobacillus rhamnosus against MCLR-induced developmental toxicity in zebrafish larvae. Zebrafish larvae were exposed to various concentrations of MCLR (0, 0.9, 1.8, and 3.6 mg/L) with or without L. rhamnosus from 72 to 168 h post-fertilization (hpf). Probiotic supplementation significantly improved survival, hatching, and growth rates and reduced malformation rates in MCLR-exposed larvae. L. rhamnosus alleviated MCLR-induced oxidative stress by reducing reactive oxygen species (ROS) levels and enhancing glutathione (GSH) content and catalase (CAT) activity. Probiotics also mitigated MCLR-induced lipid metabolism disorders by regulating key metabolites (triglycerides, cholesterol, bile acids, and free fatty acids) and gene expression (ppara, pparb, srebp1, and nr1h4). Moreover, 16S rRNA sequencing revealed that L. rhamnosus modulated the gut microbiome structure and diversity in MCLR-exposed larvae, promoting beneficial genera like Shewanella and Enterobacter and inhibiting potential pathogens like Vibrio. Significant correlations were found between gut microbiota composition and host antioxidant and lipid metabolism parameters. These findings suggest that L. rhamnosus exerts protective effects against MCLR toxicity in zebrafish larvae by alleviating oxidative stress, regulating lipid metabolism, and modulating the gut microbiome, providing insights into probiotic-based strategies for mitigating MCLR toxicity in aquatic organisms.

Proteomic and cardiac dysregulation by representative perfluoroalkyl acids of different chemical speciation during early embryogenesis of zebrafish

Perfluoroalkyl acids (PFAAs) of different chemical speciation were previously found to cause diverse toxicity. However, the toxicological mechanisms depending on chemical speciation are still largely unknown. In this follow-up study, zebrafish embryos were acutely exposed to only one concentration at 4.67 μM of the acid and salt of representative PFAAs, including perfluorooctanoic acid (PFOA), perfluorobutane carboxylic acid (PFBA), and perfluorobutanesulfonic acid (PFBS), till 96 h post-fertilization (hpf), aiming to gain more mechanistic insights. High-throughput proteomics found that PFAA acid and salt exerted discriminative effects on protein expression pattern. Bioinformatic analyses based on differentially expressed proteins underlined the developmental cardiotoxicity of PFOA acid with regard to cardiac muscle contraction, vascular smooth muscle contraction, adrenergic signaling in cardiomyocytes, and multiple terms related to myocardial contraction. PFOA salt and PFBS acid merely disrupted the cardiac muscle contraction pathway, while cardiac muscle cell differentiation was significantly enriched in PFBA acid-exposed zebrafish larvae. Consistently, under PFAA exposure, especially PFOA and PFBS acid forms, transcriptional levels of key genes for cardiogenesis and the concentrations of troponin and epinephrine associated with myocardial contraction were significantly dysregulated. Moreover, a transgenic line Tg (my17: GFP) expressing green fluorescent protein in myocardial cells was employed to visualize the histopathology of developing heart. PFOA acid concurrently caused multiple deficits in heart morphogenesis and function, which were characterized by the significant increase in sinus venosus and bulbus arteriosus distance (SV-BA distance), the induction of pericardial edema, and the decrease in heart rate, further confirming the stronger toxicity of PFOA acid than the salt counterpart on heart development. Overall, this study highlighted the developmental cardiotoxicity of PFAAs, with potency ranking PFOA > PFBS > PFBA. The acid forms of PFAAs induced stronger cardiac toxicity than their salt counterparts, providing an additional insight into the structure-toxicity relationship.

Bifidobacterium mediate gut microbiota-remedied intestinal barrier damage caused by cyproconazole in zebrafish (Danio rerio)

The widespread use of cyproconazole (CPZ) enhances food security but may pose potential risks to non-target organisms. Therefore, we applied Multi-omics techniques to reveal the response of the intestinal barrier to CPZ exposure and explore whether the Bifidobacterium intervention experiment can repair the damage. First, we found that exposure to CPZ at environmentally relevant concentrations led to intestinal injury phenotype, significantly down-regulated intestinal protein gene expression, and up-regulated pro-inflammatory gene expression, further causing intestinal dysbacteriosis and metabolic disorders. In particular, by combining analysis of gut microbiota and metabolites, we noticed acetate, a key metabolite, which decreased sharply after exposure to high concentration of CPZ. Expectedly, after supplementing with Bifidobacterium (a core bacterium that produces acetate), we noticed that the acetate content was quickly restored. Further, we also verified that the increase in acetate content after Bifidobacterium supplementation at least partially promoted IL-22 secretion, which in turn stimulated the secretion of β-defensins (zfbd-1, zfbd-2, zfbd-3), thereby repairing the intestinal damage. In conclusion, our work confirms the potential of Bifidobacterium to improve intestinal damage and metabolic dysbiosis caused by CPZ exposure. It provides directional recommendations for the application of probiotics to repair the toxicological risk of pesticide exposure.

Impact of Chlorella vulgaris Bioremediation and Selenium on Genotoxicity, Nephrotoxicity and Oxidative/Antioxidant Imbalance Induced by Polystyrene Nanoplastics in African Catfish (Clarias gariepinus)

Contamination of the environment with nano- and microplastic particles exerts a threatening impact on the aquatic ecosystems and sustainable catfish aquaculture. The presence of nanoplastics has been found to have a detrimental impact on both aquatic and terrestrial ecosystems. The present study examines the effect of polystyrene nanoplastics (PS NPs) on the DNA, erythrocytes, oxidative status and renal histology of catfish, in addition to the potential protective effects of Chlorella vulgaris bioremediation and selenium to hinder this effect. Six equal groups of fish were used as follows: Group 1 served as a control group and received water free from PS NPs; Group 2 was exposed to PS NPs at a concentration of 5 mg/L; Group 3 was exposed to PS NPs (5 mg/L) + selenium (1 mg/kg diet); Group 4 was exposed to PS NPs (5 mg/L) + C. vulgaris (25 g/kg diet); Group 5 was supplemented with C. vulgaris (25 g/kg diet); and Group 6 was supplemented with selenium (1 mg/kg diet). The exposure period was 30 days. The results indicated that PS NPs induced oxidative stress by significantly elevating malondialdehyde activities and slightly reducing antioxidant biomarkers, resulting in DNA damage, increased frequency of micronuclei, erythrocyte alterations, and numerous histopathological alterations in kidney tissue. Selenium and C. vulgaris significantly ameliorated the oxidative/antioxidant status, reducing DNA damage, micronucleus frequency, erythrocyte alterations, and improving the morphology of kidney tissue. Nevertheless, further research is needed for a profound understanding of the mechanism behind the toxicity of nano-microplatics in aquatic systems.

Hypoxic and temporal variation in the endocrine disrupting toxicity of perfluorobutanesulfonate in marine medaka (Oryzias melastigma)

Perfluorobutanesulfonate (PFBS) is an emerging pollutant capable of potently disrupting the sex and thyroid endocrine systems of teleosts. However, the hypoxic and temporal variation in PFBS endocrine disrupting toxicity remain largely unknown. In the present study, adult marine medaka were exposed to environmentally realistic concentrations of PFBS (0 and 10 µg/L) under normoxia or hypoxia conditions for 7 days, aiming to explore the interactive behavior between PFBS and hypoxia. In addition, PFBS singular exposure was extended till 21 days under normoxia to elucidate the time-course progression in PFBS toxicity. The results showed that hypoxia inhibited the growth and caused the suspension of egg spawn regardless of PFBS exposure. With regard to the sex endocrine system, 7-day PFBS exposure led to an acute stimulation of transcriptional profiles in females, which, subsequently, recovered after the 21-day exposure. The potency of hypoxia to disturb the sex hormones was much stronger than PFBS. A remarkable increase in estradiol concentration was noted in medaka blood after hypoxia exposure. Changes in sex endocrinology of coexposed fish were largely determined by hypoxia, which drove the formation of an estrogenic environment. PFBS further enhanced the endocrine disrupting effects of hypoxia. However, the hepatic synthesis of vitellogenin and choriogenin, two commonly used sensitive biomarkers of estrogenic activity, failed to initiate in response to the estrogen stimulus. Compared to sex endocrine system, disturbances in thyroidal axis by PFBS or hypoxia were relatively mild. Overall, the present findings will advance our toxicological understanding about PFBS pollutant under the interference of hypoxia.

Transcriptomics integrated with metabolomics reveals perfluorobutane sulfonate (PFBS) exposure effect during pregnancy and lactation on lipid metabolism in rat offspring

Emerging epidemiological evidence indicates potential associations between gestational perfluorobutane sulfonate (PFBS) exposure and adverse metabolic outcomes in offspring. However, the underlying mechanisms remain unclear. Our study aimed to investigate PFBS exposure effects during pregnancy and lactation on rat offspring lipid profiles and the possible underlying mechanisms. Although the biochemical index difference including total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), alanine amino transaminase (ALT), aspartate amino transferase (AST), and fasting blood glucose between exposed groups and the control group was not significant, transcriptome analyses showed that the differentially expressed genes (DEGs) in the 50 mg/kg/day PFBS exposure group were significantly related to protein digestion and absorption, peroxisome proliferator activated-receptor (PPAR) signaling pathway, xenobiotic metabolism by cytochrome P450, glycine, serine and threonine metabolism, β-alanine metabolism, bile secretion, unsaturated fatty acid (FA) biosynthesis, and alanine, aspartate and glutamate metabolism. Untargeted metabolomics analyses identified 17 differential metabolites in the 50 mg/kg/day PFBS exposure group. Among these, phosphatidylserine [PS (18:0/22:6(4Z,7Z,10Z,13Z,16Z,19Z))], lysoPE (18:1(11Z)/0:0), and PS (14:0/20:4(5Z,8Z,11Z,14Z)) were significantly correlated with phospholipid metabolism disorders. Correlation analysis indicated the DEGs, including FA binding protein (Fabp4), spermine oxidase (Smox), Fabp2, acyl-CoA thioesterase 5 (Acot5), sarcosine dehydrogenase (Sardh), and amine oxidase, copper-containing 3 (Aoc3) that significantly enriched in xenobiotic metabolism by cytochrome P450 and glycine, serine, and threonine metabolism signaling pathways were highly related to the differential metabolite pantetheine 4'-phosphate. Pantetheine 4'-phosphate was significantly negatively associated with non-high-density lipoprotein (non-HDL) and TC levels. Collectively, our study indicated that maternal PFBS exposure at a relatively low level could alter gene expression and metabolic molecules in lipid metabolism-related pathway series in rat offspring, although the effects on metabolic phenotypes were not significant within the limited observational period, using group-wise and trend analyses.

Toxicity of Per- and Polyfluoroalkyl Substances to Nematodes

Per- and polyfluoroalkyl substances (PFASs) are a class of compounds that persist in the environment globally. Besides being transported to the soil and sediments, which act as their sinks, PFASs can be transferred to several species of higher organisms directly or via bacteria, eliciting a wide range of adverse effects. Caenorhabditis elegans has been widely used in toxicological studies and life science research owing to its numerous advantages over traditional vertebrate models; notably, C. elegans has 65% conserved human-disease-associated genes and does not require ethical approvals for experimental use. This review covers a range of topics, from reported accumulation characteristics and lethal concentrations of PFAS in C. elegans to the mechanisms underlying the toxicity of PFAS at different levels, including reproductive, developmental, cellular, neurologic, oxidative, metabolic, immune, and endocrine toxicities. Additionally, the toxicity levels of some PFAS substitutes are summarized. Lastly, we discuss the toxicological mechanisms of these PFAS substitutes and the importance and promising potential of nematodes as in vivo models for life science research, epidemiological studies (obesity, aging, and Alzheimer's disease research), and toxicological investigations of PFASs and other emerging pollutants compared with other soil animals or model organisms.

Dysfunction of liver-gut axis in marine medaka exposed to hypoxia and perfluorobutanesulfonate

With objectives to explore the interactive mode on the function of liver-gut axis, adult marine medaka were exposed for 7 days to environmentally realistic concentrations of perfluorobutanesulfonate (PFBS) (0 and 10 μg/L) under normoxia or hypoxia condition. Furthermore, PFBS exposure was extended to 21 days to reveal the temporal progression in toxicity. The results showed that hypoxia exposure significantly disturbed lipid metabolism, caused oxidative damage, and induced inflammation in the livers of medaka. The composition of gut microbiota was also drastically shifted by hypoxia acute exposure. In contrast, the effect of PFBS was much milder. Hypoxia was thus the determinant of the combined toxicity. Depending on the exposure duration, a time-course recovery from PFBS innate toxicity was generally noted. Overall, the present study underlines the hypoxic and temporal variation in the dysregulation of liver-gut axis by PFBS, which is expected to support a comprehensive ecological risk assessment.

The Influence of Probiotics in Reducing Cisplatin-Induced Toxicity in Zebrafish (Danio rerio)

In this work, the effects of probiotic supplementation on cisplatin toxicity in zebrafish (Danio rerio) were examined. For this study, adult female zebrafish were given cisplatin (G2), the probiotic, Bacillus megaterium (G3), and cisplatin+B. megaterium (G4) for 30 days, in addition to the control (G1). In order to investigate changes in antioxidative enzymes, ROS production, and histological changes after treatment, the intestines and ovaries were excised. The levels of lipid peroxidation, glutathione peroxidase, glutathione reductase, catalase, and superoxide dismutase were found to be significantly higher in the cisplatin group than in the control group in both the intestine and the ovaries. Administration of the probiotic and cisplatin effectively reversed this damage. Histopathological analyses showed that the cisplatin group had much more damage than the control group and that probiotic+cisplatin treatment significantly cured these damages. It opens the door to probiotics being combined with cancer-related drugs, which may be a more efficient approach for minimizing side effects. The underlying molecular mechanisms of probiotics must be further investigated.

Dynamic changes in intestinal microbiota and metabolite composition of pre-weaned beef calves

Gut microbes and their metabolites are essential for maintaining host health and production. The intestinal microflora of pre-weaned calves gradually tends to mature with growth and development and has high plasticity, but few studies have explored the dynamic changes of intestinal microbiota and metabolites in pre-weaned beef calves. In this study, we tracked the dynamics of faecal microbiota in 13 new-born calves by 16S rRNA gene sequencing and analysed changes in faecal amino acid levels using metabolomics. Calves were divided into the relatively high average daily gain group (HA) and the relatively low average daily gain group (LA) for comparison. The results demonstrated that the alpha diversity of the faecal microbiota increased with calf growth and development. The abundance of Porphyromonadaceae bacterium DJF B175 increased in the HA group, while that of Lactobacillus reuteri decreased. The results of the LEfSe analysis showed that the microbiota of faeces of HA calves at eight weeks of age was enriched with P. bacterium DJF B175, while Escherichia coli and L. reuteri were enriched in the microbiota of faeces of LA calves. Besides, the total amino acid concentration decreased significantly in the eighth week compared with that in the first week (P < 0.05). Overall, even under the same management conditions, microorganisms and their metabolites interact to play different dynamic regulatory roles. Our results provide new insights into changes in the gut microbiota and metabolites of pre-weaned calves.

Probiotic cultures as a potential protective strategy against the toxicity of environmentally relevant chemicals: State-of-the-art knowledge

Environmentally relevant toxic substances may affect human health, provoking numerous harmful effects on central nervous, respiratory, cardiovascular, endocrine and reproductive system, and even cause various types of carcinoma. These substances, to which general population is constantly and simultaneously exposed, enter human body via food and water, but also by inhalation and dermal contact, while accumulating evidence suggests that probiotic cultures are able to efficiently adsorb and/or degrade them. Cell wall of probiotic bacteria/fungi, which contains structures such as exopolysaccharide, teichoic acid, protein and peptidoglycan components, is considered the main place of toxic substances adsorption. Moreover, probiotics are able to induce metabolism and degradation of various toxic substances, making them less toxic and more suitable for elimination. Other probable in vivo protective effects have also been suggested, including decreased intestinal absorption and increased excretion of toxic substances, prevented gut microbial dysbiosis, increase in the intestinal mucus secretion, decreased production of reactive oxygen species, reduction of inflammation, etc. Having all of this in mind, this review aims to summarize the state-of-the-art knowledge regarding the potential protective effects of different probiotic strains against environmentally relevant toxic substances (mycotoxins, polycyclic aromatic hydrocarbons, pesticides, perfluoroalkyl and polyfluoroalkyl substances, phthalates, bisphenol A and toxic metals).

Probiotics ameliorate growth retardation of glyphosate by regulating intestinal microbiota and metabolites in crucian carp (Carassius auratus)

Glyphosate (GLY) contamination widely occurred in aquatic environments including aquaculture systems and raised hazard to aquatic organisms such as fish. Probiotics have been reported to alleviate contaminants-induced toxicity. However, whether probiotics could reduce the health risk of GLY to fish remain unknown. Here we investigated the impacts of GLY on crucian carp (Carassius auratus) by focusing on the protective roles of two commonly used aquaculture probiotics, Bacillus coagulans (BC) and Clostridium butyricum (CB). Exposure to GLY significantly caused growth retardation and reduced visceral fat and intestinal lipase activity in crucian carp. 16S rRNA sequencing indicated that dysbiosis of Bacteroidetes at phylum level and Flavobacterium at genus level might be primarily responsible for GLY-induced negative growth performance. High throughput targeted quantification for metabolites revealed that GLY changed intestinal metabolites profiles, especially the reduced bile acids and short-chain fatty acids. However, the addition of BC or CB effectively attenuated the adverse effects above by remodeling the gut microbiota composition and improving microbial metabolism. The present study provides novel evidence for ameliorating the harmful effects of GLY on fish species by adding probiotics, which highlights the potential application of probiotics in reducing the health risks of GLY in aquatic environment.

Whole genome analysis of host-associated lactobacillus salivarius and the effects on hepatic antioxidant enzymes and gut microorganisms of Sinocyclocheilus grahami

As a fish unique to Yunnan Province in China, Sinocyclocheilus grahami hosts abundant potential probiotic resources in its intestinal tract. However, the genomic characteristics of the probiotic potential bacteria in its intestine and their effects on S. grahami have not yet been established. In this study, we investigated the functional genomics and host response of a strain, Lactobacillus salivarius S01, isolated from the intestine of S. grahami (bred in captivity). The results revealed that the total length of the genome was 1,737,623 bp (GC content, 33.09%), comprised of 1895 genes, including 22 rRNA operons and 78 transfer RNA genes. Three clusters of antibacterial substances related genes were identified using antiSMASH and BAGEL4 database predictions. In addition, manual examination confirmed the presence of functional genes related to stress resistance, adhesion, immunity, and other genes responsible for probiotic potential in the genome of L. salivarius S01. Subsequently, the probiotic effect of L. salivarius S01 was investigated in vivo by feeding S. grahami a diet with bacterial supplementation. The results showed that potential probiotic supplementation increased the activity of antioxidant enzymes (SOD, CAT, and POD) in the hepar and reduced oxidative damage (MDA). Furthermore, the gut microbial community and diversity of S. grahami from different treatment groups were compared using high-throughput sequencing. The diversity index of the gut microbial community in the group supplemented with potential probiotics was higher than that in the control group, indicating that supplementation with potential probiotics increased gut microbial diversity. At the phylum level, the abundance of Proteobacteria decreased with potential probiotic supplementation, while the abundance of Firmicutes, Actinobacteriota, and Bacteroidota increased. At the genus level, there was a decrease in the abundance of the pathogenic bacterium Aeromonas and an increase in the abundance of the potential probiotic bacterium Bifidobacterium. The results of this study suggest that L. salivarius S01 is a promising potential probiotic candidate that provides multiple benefits for the microbiome of S. grahami.

Lactobacillus rhamnosus GG normalizes gut dysmotility induced by environmental pollutants via affecting serotonin level in zebrafish larvae

Intestinal peristalsis is essential for gastrointestinal function, which could maintain the appropriate progression and digestion of food and reduce bacterial aggregation through mixing function. Even though certain ingredients of foodstuff are known to increase or decrease intestinal peristalsis, the role of environmental pollutants on intestinal peristalsis is relatively unknown. Therefore, the effects of four typical environmental pollutants (oxytetracycline, arsenic, polychlorinated biphenyls and chlorpyrifos) on intestinal peristalsis in the zebrafish model and then tested the recovery effect of the constipation-resistant probiotic. The results showed that 4-day environmental pollutants exposures on the zebrafish embryos at 1 day post fertilization clearly decreased the intestinal peristalsis through decreasing the serotonin (5-HT) production and down-regulating the expression of key genes involved in 5-HT synthesis. Pollutants-evoked change of gut motility could be normalized in the presence of Lactobacillus rhamnosus GG (LGG) via increasing 5-HT secretion. Exogenous 5-hydroxytryptophan (100 µg/L) could also rescue the dysfunction of gut motility in pollutants-treated zebrfish. The data identified that LGG normalized disorder of intestinal peristalsis induced by environmental pollutants through increasing 5-HT level. The stimulant effect of LGG on peristalsis may be associated with 5-HT system, which could provide references for the application of probiotics in regulation of gut dysmotility.

Metabolomic profiles in zebrafish larvae following probiotic and perfluorobutanesulfonate coexposure

Probiotic supplements are able to attenuate the developmental toxicity of perfluorobutanesulfonate (PFBS) pollutant. However, the underlying mechanisms remain unexplored. To this end, the present study acutely exposed zebrafish larvae for 4 days to 0 and 10 mg/L of PFBS, with or without the addition of probiotic Lactobacillus rhamnosus in the rearing water. The metabolomics approach was used to reveal the combined effects of PFBS and probiotics on metabolic dynamics, based on which gene transcriptions, enzymatic activities, and behavioral endpoints were further examined. The results showed that probiotic supplements were the major driver of the metabolomic fingerprints in coexposed zebrafish larvae. The addition of probiotic bacteria significantly decreased the methylation potential whilst up-regulating the demethylation process of genomic DNA, which may globally stimulate the gene expression to improve somatic growth. Acute exposure to PFBS significantly increased the cortisol concentration in zebrafish larvae, subsequently inducing stress response and hyperactive behavior. In contrast, probiotic supplementation promoted the degradation of cortisol, thus alleviating the stressful state. Antagonistic action of probiotics against PFBS developmental toxicity was also noted regarding the locomotor behavior. In addition, gut microbiota-mediated production of secondary bile acids was remarkably enhanced by probiotic supplements regardless of PFBS exposure. Overall, the present study underlines the efficacy of probiotic bacteria to protect zebrafish larvae from the metabolic disturbances of PFBS, thereby providing more evidence to support the application of probiotics in aquaculture and fishery as an environmentally-friendly choice.

Sub-Chronic Difenoconazole Exposure Induced Gut Microbiota Dysbiosis in Mice

Difenoconazole (DIF) is a widely separated triazole fungicide in many countries. The excessive usage of DIF increases the high volume of residues in agriculture production and water bodies. Some previous studies demonstrated the toxic effects of DIF on non-target animals, however, there were still some gaps in the knowledge of the potential hazards of DIF to mammals and human health. Herein, 7-week-old male mice were exposed to 30 and 100 mg/kg/day DIF for 14 and 56 days. We observed that 56 days of DIF exposure decreased the colonic mucus expression of alcin blue-periodic acid-schiff (AB-PAS) stain and the immunochemical stain of muc2 protein. The transcript levels of mucin protein (muc1, muc2 and muc3) decreased significantly in the gut of mice followed 56 days of 100 mg/kg/day DIF exposure. In addition, the gut microbiota composition was also affected after 14 or 56 days of DIF exposure. Although the mucus expression after 14 days of DIF exposure only decreased slightly, the gut microbiota composition compared with the control group was changed significantly. Moreover, the DIF-30 and DIF-100 caused respectively different changes on the gut microbiota. The relative abundance of Bacteroidetes decreased significantly after 14 days and 56 days of DIF exposure. After 14 days of DIF exposure, there were 35 and 18 differential genera in the DIF-30 and DIF-100 group, respectively. There were 25 and 32 differential genera in the DIF-30 and DIF-100 group after 56 days of exposure, respectively. Meanwhile, the alpha diversity indexes, including observed species, Shannon, Simpson, Chao1 and ACE, in gut microbiota decreased significantly after 56 days of DIF exposure. Interestingly, the relative abundance of Akkermansia increased significantly after 56 days of 100 mg/kg/d DIF exposure. Although Akkermansia was considered as one probiotic, the phenomenon of dramatic Akkermansia increase with the decrease in gut microbiota diversity needed further discussion. These results provided some new insights on how DIF exposure impacts the mucus barrier and induces gut microbiota dysbiosis.

Probiotics inhibit the stunted growth defect of perfluorobutanesulfonate via stress and thyroid axes in zebrafish larvae

Perfluorobutanesulfonate (PFBS) is an emerging pollutant in aquatic environments and potently disrupts the early developmental trajectory of teleosts. Considering the persistent and toxic nature of PFBS, it is necessary to develop in situ protective measures to ameliorate the toxic damage of PFBS. Probiotic supplements are able to mitigate the growth retardation defects of PFBS. However, the interactive mechanisms remain elusive. To this end, this study acutely exposed zebrafish larvae to a concentration gradient of PFBS (0, 1, 3.3 and 10 mg/L) for 4 days, during which probiotic bacteria Lactobacillus rhamnosus were added in the rearing water. After exposure, alterations in gene transcriptions and key hormones along the hypothalamus-pituitary-interrenal (HPI), growth hormone/insulin-like growth factor (GH/IGF) and hypothalamus-pituitary-thyroid (HPT) axes were examined. The results showed that PFBS single exposure significantly increased the cortisol concentrations, suggesting the induction of stress response, while probiotic supplementation effectively decreased the cortisol levels in coexposed larvae in an attempt to relieve the stress of PFBS toxicant. It was unexpected that probiotic additive significantly decreased the larval GH concentrations independent of PFBS, thereby eliminating the contribution of GH/IGF axis to the growth improvement of probiotics. In contrast, probiotic bacteria remarkably increased the concentration of thyroid hormones, particularly the thyroxine (T4), in zebrafish larvae. The pronounced down-regulation of uridinediphosphate glucoronosyltransferases (UDPGT) gene pointed to the blocked elimination process of T4 by probiotics. Furthermore, proteomic fingerprinting found that probiotics were potent to shape the protein expression pattern in PFBS-exposed zebrafish larvae and modulated multiple biological processes that are essential for the growth. In summary, the present findings suggest that HPI and HPT axes may cooperate to enhance the growth of fish larvae under PFBS and probiotic coexposures.