Triclosan-loaded aged microplastics exacerbate oxidative stress and neurotoxicity in Xenopus tropicalis tadpoles via increased bioaccumulation.

Microplastics and chlorine-containing triclosan (TCS) are widespread in aquatic environments and may pose health risks to organisms. However, studies on the combined toxicity of aged microplastics and TCS are limited. To investigate the toxic effects and potential mechanisms associated with co-exposure to TCS adsorbed on aged polyethylene microplastics (aPE-MPs) at environmentally relevant concentrations, a 7-day chronic exposure experiment was conducted using Xenopus tropicalis tadpoles. The results showed that the overall particle size of aPE-MPs decreased after 30 days of UV aging, whereas the increase in specific surface area improved the adsorption capacity of aPE-MPs for TCS, resulting in the bioaccumulation of TCS under dual-exposure conditions in the order of aPE-TCS > PE-TCS > TCS. Co-exposure to aPE-MPs and TCS exacerbated oxidative stress and neurotoxicity to a greater extent than a single exposure. Significant upregulation of pro-symptomatic factors (IL-ß and IL-6) and antioxidant enzyme activities (SOD and CAT) indicated that the aPE-TCS combination caused more severe oxidative stress and inflammation. Molecular docking revealed the molecular mechanism of the direct interaction between TCS and SOD, CAT, and AChE proteins, which explains why aPE-MPs promote the bioaccumulation of TCS, causing increased toxicity upon combined exposure. These results emphasize the need to be aware of the combined toxicity caused by the increased ability of aged microplastics to carry contaminants.

In 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.

Study on toxicity responses and their mechanisms in Xenopus tropicalis long-term exposure to Shigella flexneri and ciprofloxacin.

The abuse and overuse of antibiotics increased not only the exposure of aquatic animals to antibiotics but also the development of resistance in pathogenic bacteria. To investigate the effects and mechanisms of exposure, a long-term experiment lasting 120 days was conducted in which Xenopus tropicalis was exposed to single and combined stress factors of multiresistant pathogenic Shigella flexneri and ciprofloxacin (CIP). The intestinal oxidative stress, immune factors and flora, as well as the brain-gut axis correlation factors of X. tropicalis, were tracked to account for the response of aquatic animals to the exogenous pollutants. SOD activity and MDA content were significantly increased in stressed X. tropicalis (p < 0.001), while the levels of proinflammatory factors (IL-1ß, IFN-γ) were significantly reduced (p < 0.01). The content of intestinal beneficial bacteria decreased and that of harmful bacteria increased in the intestinal flora of the stressed X. tropicalis (p < 0.001). These results suggested that S. flexneri and CIP disturbed the intestinal flora and caused oxidative damage in the host, and the body produced a series of responses, such as oxidative stress responses and regulation of the expression of immune factors, to maintain the balance of antioxidant inflammation. Significant changes in the expression of intestinal neurotransmitters (5-HT, CGRP) and brain peptides (BDNF, NCAM, NPY) (p < 0.05) also indicated that the brain-gut axis interaction was disrupted. In addition, although the coexisting CIP could reduce intestinal toxicity caused by S. flexneri, the amount of intestinal pathogenic bacteria Desulfovibrio increased significantly. Moreover, compared with the single exposure group, SOD activity, CAT activity and MDA content were significantly reduced in the dual exposure group. Therefore, the health risks of multiresistant pathogenic bacteria on the intestinal and brain-gut axis interaction should be given more attention, and the interaction of brain-gut axis is more important when antibiotics coexist.

A rapid and simplified method for evaluating the performance of fungi-algae pellets: A hierarchical analysis model.

Microbial pellets technology has undergone extensive research recently and has increasingly matured, showing significant promise. However, the performance of microbial pellets cannot be predicted quickly by the current evaluating methods because they are complicated to operate, take a long time, and pose a risk to the environment. In this study, a representative microbial pellet, fungi-algae pellet, was selected as the research object. Eight evaluation parameters and four evaluation indices were chosen to construct the performance evaluation system of the fungal-algal pellets using the analytic hierarchy process (AHP) and weighting method. Combining the correlation analysis and expert opinion, we found that among the eight parameters selected, the adsorption saturation rate of mycelial pellets on algae had the most significant influence weight on the performance of fungi-algae pellet, followed by algal culture time and fungal incubation time. This research proposes and validates the Performance Evaluation Value (PEV) of fungi-algae pellet and its calculation method. We also discuss the effectiveness of this new evaluation system in saving time, cost, and emission reductions. The results of this paper enable the rapid evaluation of fungi-algae pellets and promote the better development of fungi-algae pellets technology and even other multi-microbial symbiotic pellet technologies.

A review on mycelial pellets as biological carriers: Wastewater treatment and recovery for resource and energy.

Mycelial pellets, a new environment friendly biological carrier, have received wide attention from researchers due to porosity, stability and unique biocompatibility. In this article, the theoretical basis and mechanism of mycelial pellets as a biological carrier were analyzed from the properties of mycelial pellets and the interaction between mycelial pellets and other microorganisms. This article aims to collate and present the current application and development trend of mycelial pellets as biological carriers in wastewater treatment, resource and energy recovery, especially the symbiotic particle system formed by mycelial pellets and microalgae is an important way to break through the technical bottleneck of biodiesel recovery from wastewater. This review also analyzes the research hotspots and trends of mycelial pellets as carriers in recent years, discusses the challenges faced by this technology, and puts forward corresponding solutions.

Colonization of biofilm in wastewater treatment: A review.

The attachment and colonization process of microorganisms on a carrier is an interdisciplinary research field. Through a series of physical, chemical, and biological actions, the microorganisms can eventually reproduce on the carrier. This article introduces biofilm start-up and its applications, and explores the current issues to look forward to future development directions. Firstly, the mechanism of microbial film formation is analyzed from the microbial community colonization and reproduction process. Secondly, when analyzing the factors influencing microbial membrane formation, the effect of microbial properties (e.g., genes, proteins, lipids) and external conditions (i.e., carrier, operating environment, and regulation mechanism among microbial communities) were discussed in depth. Aimed at exploring the mechanisms and influencing factors of biofilm start-up, this article proposes the application measures to strengthen this process. Finally, the problems encountered and the future development direction of the technology are analyzed and prospected.

The adsorption mechanisms of algae-bacteria symbiotic system and its fast formation process.

The formation process of the algae-bacteria symbiotic system (ABSS) was analyzed, and the formation adsorption conditions were optimized. The role of extracellular polymeric substances (EPS), specific surface area and zeta potential in adsorption mechanisms were assessed and proposed. The results showed the dry weight of the ABSS and adsorption efficiency of microalgae reached the highest under the conditions of 25 °C, pH 6.0, 160 rpm and CaCl2 2.0 mg/mL. The process of the ABSS formation could be mainly divided into the fast stage and slow stage. The roles of EPS, specific surface area and zeta potential accounted for 84.22%, 5.17% and 10.61% of the adsorption capacity, respectively. EPS dominated the formation of the ABSS. The results indicated that mycelial pellets were biosorption materials and had the characteristics of chemical materials.