Effects of Lactobacillus pentosus combined with Arthrospira platensis on the growth performance, immune response, and intestinal microbiota of Litopenaeus vannamei. - Related Documents




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601901.0000Effects of Lactobacillus pentosus combined with Arthrospira platensis on the growth performance, immune response, and intestinal microbiota of Litopenaeus vannamei. Litopenaeus vannamei is one of the most productive shrimp species in the world. However, shrimp farming is suffering from adverse environmental conditions and disease outbreaks. Typically, Lactobacillus pentosus and Arthrospira platensis are used as substitutes for some antibiotics. In the present study, we assessed the effects of dietary supplements along with living bacteria or cell-free extracts of L. pentosus combined with A. platensis on the growth performance, immune response, intestinal microbiota, and disease resistance of L. vannamei against Vibrio alginolyticus. Shrimp fed L. pentosus live bacteria combined with A. platensis showed the best growth performance and lowest feed conversion rate. The supplementation diet with L. pentosus live bacteria and A. platensis could significantly enhance the trypsin activity in shrimp after the feeding trial. Given the lowest feed conversion rate in shrimp fed L. pentosus live bacteria combined with A. platensis, we reasonably speculated that the decrease in feed conversion rate may be related to the increase in trypsin activity. In addition, dietary cell-free extracts of L. pentosus combined with A. platensis enhanced the expression of immune-related genes after the feeding trial or challenge test. Moreover, results of the bacterial challenge test indicated that the shrimp fed cell-free extracts of L. pentosus combined with A. platensis diet resulted in the highest survival rate, which suggested that cell-free extracts of L. pentosus and A. platensis could improve the disease resistance against V. alginolyticus by up-regulating the expressions of immune-related genes. Dietary L.pentosus or A. platensis, or their combination, reduced the abundance of harmful bacteria, including Proteobacteria in shrimp intestine, which suggested that L. pentosus and A. platensis could improve the growth performance and health of shrimp by regulating the structure of the intestinal microbiota. The findings of this study demonstrated that L. pentosus live bacteria and A. platensis exerted synergistic effects on the growth performance and digestion in shrimp, while cell-free extracts of L. pentosus and A. platensis showed synergistic effects on the immune response and disease resistance of shrimp against V. alginolyticus.202234883257
601810.9992Effect of Trehalose and Lactose Treatments on the Freeze-Drying Resistance of Lactic Acid Bacteria in High-Density Culture. Freeze-drying is a commonly used method in commercial preparations of lactic acid bacteria. However, some bacteria are killed during the freeze-drying process. To overcome this, trehalose and lactose are often used as protective agents. Moreover, high-density culture is an efficient way to grow bacterial strains but creates a hypertonic growth environment. We evaluated the effects of trehalose and lactose, as a primary carbon source or as an additive in fermentation, on the freeze-drying survival of Lactobacillus fermentum FXJCJ6-1, Lactobacillus brevis 173-1-2, and Lactobacillus reuteri CCFM1040. Our results showed that L. fermentum FXJCJ6-1 accumulated but did not use intracellular trehalose in a hypertonic environment, which enhanced its freeze-drying resistance. Furthermore, genes that could transport trehalose were identified in this bacterium. In addition, both the lactose addition and lactose culture improved the freeze-drying survival of the bacterium. Further studies revealed that the added lactose might exert its protective effect by attaching to the cell surface, whereas lactose culture acted by reducing extracellular polysaccharide production and promoting the binding of the protectant to the cell membrane. The different mechanisms of lactose and trehalose in enhancing the freeze-drying resistance of bacteria identified in this study will help to elucidate the anti-freeze-drying mechanisms of other sugars in subsequent investigations.202236677339
15820.9991Homology- and cross-resistance of Lactobacillus plantarum to acid and osmotic stress and the influence of induction conditions on its proliferation by RNA-Seq. In this study, homology- and cross-resistance of Lactobacillus plantarum L1 and Lactobacillus plantarum L2 to acid and osmotic stress were investigated. Meanwhile, its proliferation mechanism was demonstrated by transcriptomic analysis using RNA sequencing. We found that the homologous-resistance and cross-resistance of L. plantarum L1 and L. plantarum L2 increased after acid and osmotic induction treatment by lactic acid and sodium lactate solution in advance, and the survival rate of live bacteria was improved. In addition, the count of viable bacteria of L. plantarum L2 significantly increased cultivated at a pH 5.0 with a 15% sodium lactate sublethal treatment, compared with the control group. Further study revealed that genes related to membrane transport, amino acid metabolism, nucleotide metabolism, and cell growth were significantly upregulated. These findings will contribute to promote high-density cell culture of starter cultures production in the fermented food industry.202133945164
674330.9991Impact of acute and chronic exposure to sulfamethoxazole on the kinetics and microbial structure of an activated sludge community. The aim of this study was to reveal the microbial and kinetic impacts of acute and chronic exposure to one of the frequently administered antibiotics, i.e., sulfamethoxazole, on an activated sludge biomass. Respirometric analysis and model evaluation of the oxygen utilization rate profiles were the backbone of this study. The results showed that continuous exposure to sulfamethoxazole resulted in the inhibition of substrate storage and an increase in the endogenous decay rates by twofold, which was supported by analysis of the resistance genes. A mild inhibition on the growth and hydrolysis kinetics was also observed. Moreover, sulfamethoxazole had a binding impact with available organic carbon, resulting in a slightly less oxygen consumption. DNA sequencing and antibiotic resistance gene analyses showed that continuous exposure to sulfamethoxazole caused a change in the community structure at the species level. Resistant bacteria including Arthrobacter sp. and members of the Chitinophagaceae and Intrasporangiaceae families were found to have dominated the bacterial community. The impact of intermittent exposure was also investigated, and the results indicated a drop in the severity of the impact after 20 days of intermittence.202439816257
385840.9991Intestinal toxicity and resistance gene threat assessment of multidrug-resistant Shigella: A novel biotype pollutant. Multidrug-resistant bacteria, especially pathogens, pose a serious threat to disease treatment and recovery, but their potential toxicity to animal development is not entirely clear. As the most important site for nutrient absorption, we studied the intestinal microbiome of Xenopus tropicalis by analyzing the effect of multidrug-resistant Shigella on its intestinal health. Unlike in the control, Shigella intake promoted the secretion of neutral mucus and inhibited intestinal development and weight gain. Following 60 days of exposure, intestinal crypt atrophy, intestinal villus shortening, internal cavity enlargement, and external mucosal muscle disintegration were observed. The circular and longitudinal intestinal muscles became thinner with increasing pathogen exposure. In addition, the presence of Shigella altered the expression of multiple cytokines and classic antioxidant enzyme activities in the gut, which may have caused the intestinal lesions that we observed. 16 S rDNA sequencing analysis of intestinal samples showed that exposure to Shigella destroyed the normal gut microbial abundance and diversity and increased the functional bacterial ratio. Notably, the increased abundance of intestinal antibiotic resistance genes (ARGs) may imply that the resistance genes carried by Shigella easily migrate and transmit within the intestine. Our results expand existing knowledge concerning multidrug-resistant Shigella-induced intestinal toxicity in X. tropicalis and provide new insights for the threat assessment of resistance genes carried by drug-resistant pathogens.202336332708
759550.9991Performance and microbial community variations of anaerobic digesters under increasing tetracycline concentrations. The impact of different concentrations of tetracycline on the performance of anaerobic treatment was evaluated. Results revealed that for all of the tested tetracycline concentrations, no major sustained impact on methane production was observed. Instead, a significant increase in propionic acid was observed in the reactor subjected to the highest concentration of tetracycline (20 mg/L). Microbial community analyses suggest that an alternative methanogenic pathway, specifically that of methanol-utilizing methanogens, may be important for ensuring the stability of methane production in the presence of high tetracycline concentrations. In addition, the accumulation of propionate was due to an increase in volatile fatty acids (VFA)-producing bacteria coupled with a reduction in propionate utilizers. An increase in the abundance of tetracycline resistance genes associated with ribosomal protection proteins was observed after 30 days of exposure to high concentrations of tetracycline, while other targeted resistance genes showed no significant changes. These findings suggest that anaerobic treatment processes can robustly treat wastewater with varying concentrations of antibiotics while also deriving value-added products and minimizing the dissemination of associated antibiotic resistance genes.201728365798
895460.9991Effect of biofilm formation by antimicrobial-resistant gram-negative bacteria in cold storage on survival in dairy processing lines. Antimicrobial-resistant gram-negative bacteria in dairy products can transfer antimicrobial resistance to gut microbiota in humans and can adversely impact the product quality. In this study, we aimed to investigate their distribution in dairy processing lines and evaluate biofilm formation and heat tolerance under dairy processing line-like conditions. Additionally, we compared the relative expression of general and heat stress-related genes as well as spoilage-related gene between biofilm and planktonic cells under consecutive stresses, similar to those in dairy processing lines. Most species of gram-negative bacteria isolated from five different dairy processing plants were resistant to one or more antimicrobials. Biofilm formation by the bacteria at 5 °C increased with the increase in exposure time. Moreover, cells in biofilms remained viable under heat treatment, whereas all planktonic cells of the selected strains died. The expression of heat-shock-related genes significantly increased with heat treatment in the biofilms but mostly decreased in the planktonic cells. Thus, biofilm formation under raw milk storage conditions may improve the tolerance of antimicrobial-resistant gram-negative bacteria to pasteurization, thereby increasing their persistence in dairy processing lines and products. Furthermore, the difference in response to heat stress between biofilm and planktonic cells may be attributed to the differential expression of heat stress-related genes. Therefore, this study contributes to the understanding of how gram-negative bacteria persist under consecutive stresses in dairy processing procedures and the potential mechanism underlying heat tolerance in biofilms.202336436412
851470.9991Graphene oxide influences transfer of plasmid-mediated antibiotic resistance genes into plants. As an emerging contaminant, antibiotic resistance genes (ARGs) are raising concerns about its significant threat to public health. Meanwhile, graphene oxide (GO), which also has a potential ecological damage with increasingly entering the environment, has a great influence on the transfer of ARGs. However, little is known about the effects mechanisms of GO on the migration of antibiotic resistance genes (ARGs) from bacteria into plants. In this study, we investigated the influence of GO on the transfer of ARGs carried by RP4 plasmids from Bacillus subtilis into rice plants. Our results showed that the presence of GO at concentrations ranging from 0 to 400 mg L(-1) significantly reduced the transfer of ARGs into rice roots by 13-71 %. Moreover, the migration of RP4 from the roots to aboveground parts was significantly impaired by GO. These effects may be attributed to several factors. First, higher GO concentrations led to low pH in the culture solution, resulting in a substantial decrease in the number of antibiotic-resistant bacteria. Second, GO induced oxidative stress in rice, as indicated by enhanced Evans blue dye staining, and elevated levels of malondialdehyde, nitric oxide, and phenylalanine ammonia-lyase activity. The oxidative stress negatively affected plant growth, as demonstrated by the reduced fresh weight and altered lignin content in the rice. Microscopic observations confirmed the entry of GO into root cells but not leaf mesophyll cells. Furthermore, potential recipients of RP4 plasmid strains in rice after co-cultivation experiments were identified, including Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus cereus. These findings clarify the influence of GO on ARGs in the bacteria-plant system and emphasize the need to consider its potential ecological risks.202437979849
763980.9990Structural and Functional Changes of Groundwater Bacterial Community During Temperature and pH Disturbances. In this study, we report the characteristics of a microbial community in sampled groundwater and elucidate the effects of temperature and pH disturbances on bacterial structure and nitrogen-cycling functions. The predominant phyla of candidate OD1, candidate OP3, and Proteobacteria represented more than half of the total bacteria, which clearly manifested as a "low nucleic acid content (LNA) bacteria majority" type via flow cytometric fingerprint. The results showed that LNA bacteria were more tolerant to rapid changes in temperature and pH, compared to high nucleic acid content (HNA) bacteria. A continuous temperature increase test demonstrated that the LNA bacterial group was less competitive than the HNA bacterial group in terms of maintaining their cell intactness and growth potential. In contrast, the percentage of intact LNA bacteria was maintained at nearly 70% with pH decrease, despite a 50% decrease in total intact cells. Next-generation sequencing results revealed strong resistance and growth potential of phylum Proteobacteria when the temperature increased or the pH decreased in groundwater, especially for subclasses α-, β-, and γ-Proteobacteria. In addition, relative abundance of nitrogen-related functional genes by qPCR showed no difference in nitrifiers or denitrifiers within 0.45 μm-captured and 0.45 μm-filterable bacteria due to phylogenetic diversity. One exception was the monophyletic anammox bacteria that belong to the phylum Planctomycetes, which were mostly captured on a 0.45-μm filter. Furthermore, we showed that both temperature increase and pH decrease could enhance the denitrification potential, whereas the nitrification and anammox potentials were weakened.201930706112
675090.9990Viable but non-culturable E. coli induced by low level chlorination have higher persistence to antibiotics than their culturable counterparts. Disinfectant used in drinking water treatment and distribution system can induce culturable bacteria, including various kinds of pathogenic bacteria, into viable but non-culturable (VBNC) state. The loss of cultural state, resuscitation and environmental persistence of VBNC bacteria will severely damage drinking water microbiological safety and thus pose a risk to public health. The manner in which chlorination treatment induced a VBNC state in Escherichia coli and the antibiotic persistence of VBNC bacteria was investigated. It was found that low dosage of chlorine (0.5 mg L(-1)) disinfection effectively reduced the culturability of E. coli and induced a VBNC state, after which metabolic activity was reduced and persistence to 9 typical antibiotics was enhanced. Furthermore, RT-qPCR results showed that stress resistance genes (rpoS, marA, ygfA, relE) and ARGs, especially efflux genes were up-regulated compared with culturable cells. The intracellular concentration was tested and found to be lower in VBNC cells than in actively growing E. coli, which suggested a higher efflux rate. The data presented indicate that VBNC E. coli are more persistent than culturable counterparts to a wide variety of antibiotics. VBNC E. coli constitute a potential source of contamination and should be considered during monitoring of drinking water networks.201728662489
7955100.9990Fluoroquinolone antibiotics disturb the defense system, gut microbiome, and antibiotic resistance genes of Enchytraeus crypticus. Antibiotic residues from animal manure cause soil pollution and can pose a threat to soil animals. In this study, the toxicological effects of fluoroquinolone antibiotics on Enchytraeus crypticus, including defence response, gut microbiome, and antibiotic resistance genes (ARGs), were studied. The cytochrome P450 enzyme activity and reactive oxygen species levels increased, activating the defense response. The superoxide dismutase and glutathione S-transferase activity, and the expression of immune defense molecules such as coelomic cytolytic factor, lysozyme, bactericidal protein fetidins and lysenin changed. Furthermore, the diversity of the gut microbiome decreased, and the relative abundance of Bacteroidetes decreased significantly at the phylum level but increased in pathogenic and antibiotic-secreting bacteria (Rhodococcus and Streptomyces) at the genus level. However, the soil microbiome was not significantly different from that of the control group. The relative abundance of ARGs in the gut and soil microbiome significantly increased with enrofloxacin concentration, and the fluoroquinolone ARGs were significantly increased in both the soil (20.85-fold, p < 0.001) and gut (11.72-fold, p < 0.001) microbiomes. Subtypes of ARGs showed a positive correlation with Rhodococcus, which might increase the risk of disease transmission and the probability of drug-resistant pathogens. Furthermore, mobile genetic elements significantly promote the spread of ARGs.202234736185
7582110.9990Anaerobic fermentation for hydrogen production and tetracycline degradation: Biodegradation mechanism and microbial community succession. The misuse and continues discharge of antibiotics can cause serious pollution, which is urgent to take steps to remit the environment pollution. In this study, anaerobic bacteria isolated from the aeration tank of a local sewage treatment plant were employed to investigate hydrogen production and tetracycline (TC) degradation during anaerobic fermentation. Results indicate that low concentrations of TC enhanced hydrogen production, increasing from 366 mL to a maximum of 480 mL. This increase is attributed to stimulated hydrolysis and acidogenesis, coupled with significant inhibition of homoacetogenesis. Furthermore, the removal of TC, facilitated by adsorption and biodegradation, exceeded 90 %. During the fermentation process, twenty-one by-products were identified, leading to the proposal of four potential degradation pathways. Analysis of the microbial community revealed shifts in diversity and a decrease in the abundance of hydrogen-producing bacteria, whereas bacteria harboring tetracycline resistance genes became more prevalent. This study provides a possibility to treat tetracycline-contaminated wastewater and to produce clean energy simultaneously by anaerobic fermentation.202439168318
6746120.9990Environmental concentration of the quaternary ammonium disinfectant benzalkonium chloride strongly induces resistance gene profiles in fish. Disinfectants are non-antibiotic biocides that have been used extensively in daily life, particularly since the onset of the COVID-19 pandemic. However, their effect on drug resistance has not received sufficient attention. Here, marine medaka were subjected to an environmental concentration (10 μg/L) of benzalkonium chloride (BAC), sulfamethazine (SMZ), and their combination, aiming to elucidate their contributions to antibiotic resistance. Overall, 10 μg/L BAC exhibited a stronger induction potential for multiple antibiotic resistance genes (ARGs) relative to a similar level of SMZ. Specifically, tetracycline resistance genes were readily induced, regardless of exposure to BAC, SMZ, or their combination. BAC exhibited a more pronounced induction of ARGs than SMZ and showed a stronger potential to stimulate multidrug resistance. SMZ and BAC induced distinct virulence factors. Bacteria increased pathogenicity primarily through biofilm formation and enhanced community sensing under SMZ exposure, whereas iron acquisition and the production of reactive oxygen species appeared to be the main mechanisms by which bacteria evaded host defenses under BAC exposure. A greater number of ARGs demonstrated a significant positive correlation with virulence factors following BAC exposure compared to both the SMZ exposure group and the co-exposure group, which further confirmed the strong ability of BAC to induce multidrug resistance. In summary, owing to the typically unregulated and low-dose use of disinfectants in daily life and their pseudo-persistence in the environment, their potential to induce resistance may exceed that of antibiotics. Therefore, increased attention and preventive measures are required to address their resistance-inducing effects.202540073566
7637130.9990High-sugar, high-fat, and high-protein diets promote antibiotic resistance gene spreading in the mouse intestinal microbiota. Diet can not only provide nutrition for intestinal microbiota, it can also remodel them. However, is unclear whether and how diet affects the spread of antibiotic resistance genes (ARGs) in the intestinal microbiota. Therefore, we employed selected high-sugar, high-fat, high-protein, and normal diets to explore the effect. The results showed that high-sugar, high-fat, and high-protein diets promoted the amplification and transfer of exogenous ARGs among intestinal microbiota, and up-regulated the expression of trfAp and trbBp while significantly altered the intestinal microbiota and its metabolites. Inflammation-related products were strongly correlated with the spread of ARGs, suggesting the intestinal microenvironment after diet remodeling might be conducive to the spreading of ARGs. This may be attributed to changes in bacterial membrane permeability, the SOS response, and bacterial composition and diversity caused by diet-induced inflammation. In addition, acceptor bacteria (zygotes) screened by flow cytometry were mostly Proteobacteria, Firmicutes and Actinobacteria, and most were derived from dominant intestinal bacteria remodeled by diet, indicating that the transfer of ARGs was closely linked to diet, and had some selectivity. Metagenomic results showed that the gut resistance genome could be affected not only by diet, but by exogenous antibiotic resistant bacteria (ARB). Many ARG markers coincided with bacterial markers in diet groups. Therefore, dominant bacteria in different diets are important hosts of ARGs in specific dietary environments, but the many pathogenic bacteria present may cause serious harm to human health.202235030982
8973140.9990Enhanced myco-synthesis of selenium and zinc oxide nanoparticles and evaluating their anticancer activities and role against antibiotic resistance genes in certain bacterial strains. BACKGROUND: In an array to check microbial resistance against generally used antibiotics, it is essential to create innovative and efficient antimicrobial agents. Therefore, nanoparticles (NPs) with their antimicrobial activities describe an effective solution. In this study, we synthesized Selenium nanoparticles (Se-NPs) and zinc oxide nanoparticles (ZnO-NPs) using Alternaria alternata fungus, then their characterization were evaluated using several techniques. RESULTS: We explored the potential of antimicrobial impact of Se-NPs and ZnO-NPs against negative and positive grams antibiotic resistance bacterial strains in combination with penicillin, Ceftriaxone and Cefipime. Moreover, antibiotic resistance gene expression was assessed after those treatments. The results demonstrated that Se-NPs and ZnO-NPs displayed antibacterial properties, while the expression of antibiotic resistance genes decreased when exposed to a combination of NPs and antibiotics. This suggests the presence of both synergistic and additive effects in these treatments. Furthermore, the cytotoxic effects of Se-NPs and ZnO-NPs were assessed, revealing their potent anticancer properties against MCF-7, A549, and HepG2 cancer cells and lower cytotoxic values for HFB-4 standard cell line. Ultimately, the production efficiency of both NPs was enhanced through gamma irradiation. CONCLUSIONS: According to the results, it seems that the green synthesis of Se-NPs and ZnO-NPs promotes environmental sustainability and cost-effective approach. This study provides insights into the development of new antibacterial and anticancer agents . The eco-friendly production of nanoparticles suggests also a sustainable approach to combating bacteria resistant to antibiotics.202541046259
6747150.9990Tetracycline accumulation in biofilms enhances the selection pressure on Escherichia coli for expression of antibiotic resistance. Microorganisms are present as either biofilm or planktonic species in natural and engineered environments. Little is known about the selection pressure emanating from exposure to sub-minimal inhibitory concentration of antibiotics on planktonic vs. biofilm bacteria. In this study, an E. coli bioreporter was used to develop biofilms on glass and high-density polyethylene (HDPE) surfaces, and compared with the corresponding planktonic bacteria in antibiotic resistance expression when exposed to a range of μg/L levels of tetracycline. The antibiotic resistance-associated fluorescence emissions from biofilm E. coli reached up to 1.6 times more than those from planktonic bacteria. The intensively developed biofilms on glass surfaces caused the embedded bacteria to experience higher selection pressure and express more antibiotic resistance than those on HDPE surfaces. The temporal pattern of fluorescence emissions from biofilm E. coli was consistent with the biofilm-developing processes during the experimental period. The increased expression of antibiotic resistance from biofilm bacteria could be attributed to the high affinity of tetracycline with extracellular polymeric substances (EPS). The enhanced accumulation of tetracycline in biofilms could exert higher selection pressure on the embedded bacteria. These results suggest that in many natural and engineered systems the higher antibiotic resistance in biofilm bacteria could be attributed partially to the retention antibiotics by the EPS in biofilms.202336252660
4714160.9990Screening and genome analysis of heat-resistant and antioxidant lactic acid bacteria from Holstein cow milk. BACKGROUND: Heat stress significantly impacts dairy cows, primarily through oxidative stress, which undermines their health. The problem is exacerbated by the ongoing global warming trend. Lactic acid bacteria (LAB) are safe, economical, and readily accessible options for enhancing the host's antioxidant defenses and preventing oxidative damage. They have been proven effective in alleviating heat stress-related damage, making them an excellent choice for protecting dairy cows from the adverse effects of heat stress. METHOD: In this study, five strains of LAB from Holstein cow milk (Lactobacillus plantarum L5, L14, L17, L19, L20) were evaluated for their heat resistance and antioxidant capacity by evaluating the growth characteristics and tolerance of the strains under high-temperature conditions, as well as their H(2)O(2) tolerance, free radical scavenging ability (DPPH, OH(-), ABTS), reducing ability, and EPS production ability. Furthermore, we employed Caco-2 cells to assess the adhesion rate of the strain, thereby confirming its ability to successfully colonize the host's intestinal tract and ensuring the effective execution of its probiotic functions. The strain with excellent heat resistance and antioxidant capacity was then subjected to genomic analysis to gain insight into the molecular mechanisms behind their heat resistance, antioxidant capacity, and safety. RESULTS: Among the two strains, Lactobacillus plantarum L19 emerges as a highly promising candidate. The strain exhibits robust growth even at high temperatures at 40°C and maintains a survival rate of 16.42% at the extreme temperature of 65°C. Furthermore, it demonstrates superior tolerance to hydrogen peroxide (27.3%), and possesses a notably higher free radical scavenging capacity with a high adhesion rate to Caco-2 cell (22.19%) compared to the other four strains tested. Genomic analysis revealed its' genome has 17 genes related to antioxidants and three genes related to heat resistance. Importantly, L19 lacks any resistance genes, ensuring its safety as a probiotic. CONCLUSION: The results imply that Lactobacillus plantarum L19 has the potential to serve as an effective food additive in mitigating damages associated with heat stress. This research offers a valuable reference for the prevention and management of heat stress in dairy cows, while also expanding the scope of applications for LAB derived from cow milk.202439611093
6748170.9990Time-dependent effects of ZnO nanoparticles on bacteria in an estuarine aquatic environment. Many studies have examined the acute toxicity of nanoparticles (NPs) towards model bacteria. In this study, we report the time-dependent effects of ZnO NPs on native, selected Zn-resistant and dominant bacteria in estuarine waters. An initial inhibition of bacterial growth followed by a recovery at 24 h was observed, and this rebound phenomenon was particularly notable when the raw water samples were treated with relatively high ZnO NP concentrations (1 and 10 mg/L).By comparing the groups treated with Zn(2+), Zn(2+) was shown to largely explain the acute cytotoxic effect of ZnO NPs on bacteria in raw waters. Furthermore, similar to the native bacteria, especially the dominant bacteria, the viability of Escherichia coli (E. coli) decreased with the increasing treatments time and the concentrations of ZnO NPs in water with different salinities. Moreover, the expression of Zn-resistance genes including zntA and zntR in E. coli suggested that the Zn-resistance system in E. coli can be activated to defend against the stress of Zn(2+) released from ZnO NPs, and salinity may promote this process in estuarine aquatic systems. Thus, the effect of ZnO NPs on bacteria in estuarine water bodies is likely determined by the synergistic effect of environmental salinity and dissolved Zn ions. As such, our findings are of high relevance and importance for understanding the ecological disturbances caused by anthropogenic NPs in estuarine environments.202031505343
8515180.9990In vitro assessment of the bacterial stress response and resistance evolution during multidrug-resistant bacterial invasion of the Xenopus tropicalis intestinal tract under typical stresses. The intestinal microbiome might be both a sink and source of resistance genes (RGs). To investigate the impact of environmental stress on the disturbance of exogenous multidrug-resistant bacteria (mARB) within the indigenous microbiome and proliferation of RGs, an intestinal conjugative system was established to simulate the invasion of mARB into the intestinal microbiota in vitro. Oxytetracycline (OTC) and heavy metals (Zn, Cu, Pb), commonly encountered in aquaculture, were selected as typical stresses for investigation. Adenosine 5'-triphosphate (ATP), hydroxyl radical (OH·(-)) and extracellular polymeric substance (EPS) were measured to investigate their influence on the acceptance of RGs by intestinal bacteria. The results showed that the transfer and diffusion of RGs under typical combined stressors were greater than those under a single stressor. Combined effect of OTC and heavy metals (Zn, Cu) significantly increased the activity and extracellular EPS content of bacteria in the intestinal conjugative system, increasing intI3 and RG abundance. OTC induced a notable inhibitory response in Citrobacter and exerted the proportion of Citrobacter and Carnobacterium in microbiota. The introduction of stressors stimulates the proliferation and dissemination of RGs within the intestinal environment. These results enhance our comprehension of the typical stresses effect on the RGs dispersal in the intestine.202438280323
6769190.9990Simulated Gastric Acid Promotes the Horizontal Transfer of Multidrug Resistance Genes across Bacteria in the Gastrointestinal Tract at Elevated pH Levels. The assessment of factors that can promote the transmission of antibiotic resistance genes (ARGs) across bacteria in the gastrointestinal tract is in great demand to understand the occurrence of infections related to antibiotic-resistant bacteria (ARB) in humans. However, whether acid-resistant enteric bacteria can promote ARG transmission in gastric fluid under high-pH conditions remains unknown. This study assessed the effects of simulated gastric fluid (SGF) at different pH levels on the RP4 plasmid-mediated conjugative transfer of ARGs. Moreover, transcriptomic analysis, measurement of reactive oxygen species (ROS) levels, assessment of cell membrane permeability, and real-time quantitative assessment of the expression of key genes were performed to identify the underlying mechanisms. The frequency of conjugative transfer was the highest in SGF at pH 4.5. Antidepressant consumption and certain dietary factors further negatively impacted this situation, with 5.66-fold and 4.26-fold increases in the conjugative transfer frequency being noted upon the addition of sertraline and 10% glucose, respectively, compared with that in the control group without any additives. The induction of ROS generation, the activation of cellular antioxidant systems, increases in cell membrane permeability, and the promotion of adhesive pilus formation were factors potentially contributing to the increased transfer frequency. These findings indicate that conjugative transfer could be enhanced under certain circumstances in SGF at elevated pH levels, thereby facilitating ARG transmission in the gastrointestinal tract. IMPORTANCE The low pH of gastric acid kills unwanted microorganisms, in turn affecting their inhabitation in the intestine. Hence, studies on the factors that influence antibiotic resistance gene (ARG) propagation in the gastrointestinal tract and on the underlying mechanisms are limited. In this study, we constructed a conjugative transfer model in the presence of simulated gastric fluid (SGF) and found that SGF could promote the dissemination of ARGs under high-pH conditions. Furthermore, antidepressant consumption and certain dietary factors could negatively impact this situation. Transcriptomic analysis and a reactive oxygen species assay revealed the overproduction of reactive oxygen species as a potential mechanism by which SGF could promote conjugative transfer. This finding can help provide a comprehensive understanding of the bloom of antibiotic-resistant bacteria in the body and create awareness regarding the risk of ARG transmission due to certain diseases or an improper diet and the subsequent decrease in gastric acid levels.202337070984