The two-component system TtrRS boosts Vibrio parahaemolyticus colonization by exploiting sulfur compounds in host gut.

One of the greatest challenges encountered by enteric pathogens is responding to rapid changes of nutrient availability in host. However, the mechanisms by which pathogens sense gastrointestinal signals and exploit available host nutrients for proliferation remain largely unknown. Here, we identified a two-component system in Vibrio parahaemolyticus, TtrRS, which senses environmental tetrathionate and subsequently activates the transcription of the ttrRS-ttrBCA-tsdBA gene cluster to promote V. parahaemolyticus colonization of adult mice. We demonstrated that TsdBA confers the ability of thiosulfate oxidation to produce tetrathionate which is sensed by TtrRS. TtrRS autoregulates and directly activates the transcription of the ttrBCA and tsdBA gene clusters. Activated TtrBCA promotes bacterial growth under micro-aerobic conditions by inducing the reduction of both tetrathionate and thiosulfate. TtrBCA and TsdBA activation by TtrRS is important for V. parahaemolyticus to colonize adult mice. Therefore, TtrRS and their target genes constitute a tetrathionate-responsive genetic circuit to exploit the host available sulfur compounds, which further contributes to the intestinal colonization of V. parahaemolyticus.

Lipid metabolism analysis providing insights into nonylphenol multi-toxicity mechanism.

Nonylphenol (NP), a widely recognized endocrine disruptor, exhibits lipophobic properties that drive its accumulation in adipose tissue, leading to various physiological disruptions. Using Caenorhabditis elegans, this study investigated the effects of NP exposure on lipid homeostasis and physiological indicators. NP exposure increased lipid storage, hindered reproduction and growth, and altered phospholipid composition. Transcriptional analysis revealed NP's promotion of lipogenesis and inhibition of lipolysis. Metabolites related to lipid metabolism like citrate, amino acids, and neurotransmitters, along with lipids, collectively influenced physiological processes. This work elucidates the complex link between lipid metabolism disturbances and NP-induced physiological disruptions, enhancing our understanding of NP's multifaceted toxicity.

Quorum sensing signal synthases enhance Vibrio parahaemolyticus swarming motility.

Vibrio parahaemolyticus is a significant food-borne pathogen that is found in diverse aquatic habitats. Quorum sensing (QS), a signaling system for cell-cell communication, plays an important role in V. parahaemolyticus persistence. We characterized the function of three V. parahaemolyticus QS signal synthases, CqsAvp , LuxMvp , and LuxSvp , and show that they are essential to activate QS and regulate swarming. We found that CqsAvp , LuxMvp , and LuxSvp activate a QS bioluminescence reporter through OpaR. However, V. parahaemolyticus exhibits swarming defects in the absence of CqsAvp , LuxMvp , and LuxSvp , but not OpaR. The swarming defect of this synthase mutant (termed Δ3AI) was recovered by overexpressing either LuxOvp D47A , a mimic of dephosphorylated LuxOvp mutant, or the scrABC operon. CqsAvp , LuxMvp , and LuxSvp inhibit lateral flagellar (laf) gene expression by inhibiting the phosphorylation of LuxOvp and the expression of scrABC. Phosphorylated LuxOvp enhances laf gene expression in a mechanism that involves modulating c-di-GMP levels. However, enhancing swarming requires phosphorylated and dephosphorylated LuxOvp which is regulated by the QS signals that are synthesized by CqsAvp , LuxMvp , and LuxSvp . The data presented here suggest an important strategy of swarming regulation by the integration of QS and c-di-GMP signaling pathways in V. parahaemolyticus.

Performance evaluation of the UV activated chlorite process on trimethoprim: Degradation efficiency, energy consumption and disinfection by-products formation.

As the primary inorganic by-product species of ClO2, chlorite is believed to have negative toxicological effects on human health and therefrom greatly limits the wide application of ClO2 in water treatment. The synergistic trimethoprim (TMP) removal concerning degradation efficiency, energy consumption and disinfection by-products (DBPs) formation in the UV activated chlorite process accompanied by the simultaneously elimination of chlorite was comprehensively evaluated. UV/chlorite integrated process removed TMP far more rapidly than UV (1.52%) or chlorite (3.20%) alone due to the endogenous radicals (Cl•, ClO• and •OH), the contributing proportions of which were 31.96%, 19.20% and 44.12%. The second-order rate constants of TMP reaction with Cl•, ClO• and •OH were determined to be 1.75 × 1010, 1.30 × 109 and 8.66 × 109 M-1 s-1. The effects of main water parameters including chlorite dosage, UV intensity, pH as well as water matrixes (nature organic matter, Cl- and HCO3-) were examined. kobs obeyed the order as UV/Cl2>UV/H2O2≈UV/chlorite>UV, and the cost ranking via electrical energy per order (EE/O, kWh m-3 order-1) parameter was UV/chlorite (3.7034) > UV/H2O2 (1.1625) >UV/Cl2 (0.1631). The operational scenarios can be optimized to achieve the maximum removal efficiencies and the minimum energy costs. The destruction mechanisms of TMP were proposed by LC-ESI-MS analysis. The overall weighted toxicity in subsequent disinfection was assessed as UV/Cl2>UV/chlorite > UV, the values of which in post-chlorination were 6.2947, 2.5806 and 1.6267, respectively. Owing to the vital roles of reactive chlorine species (RCS), UV/chlorite displayed far higher TMP degradation efficiency than UV, and concurrently presented much less toxicity than UV/Cl2. In an effort to determine the viability of the promising combination technology, this study was devoted to reduce and reuse chlorite and synchronously realize the contaminants degradation efficiently.

Continuous and discontinuous multi-generational disturbances of tetrabromobisphenol A on longevity in Caenorhabditis elegans.

Tetrabromobisphenol A (TBBPA) is one of the most prevalently used brominated flame retardants. Due to its persistence, it is predominantly found in environmental matrices and has the potential to generate multi-generational toxicity. However, knowledge of its adaptive response or long-term residual effect in multi-generations, and molecular mechanisms remain understudied. In the current study, the model animal nematode Caenorhabditis elegans (C. elegans) was exposed to TBBPA at environmentally realistic concentrations (0.1-1000 µg L-1) for four consecutive generations (G0 to G3). Degenerative age-related multiple endpoints including lifespan, locomotion behaviors, growth, reproduction, oxidative stress-related biochemical responses, cell apoptosis, and stress related gene expressions were assessed in the continuous exposure generations (G0 and G3) and the discontinuously exposed generations (T3 and T'3). The results showed that changes in degenerative age-related response monitored four generations varied in direction and magnitude depending on the TBBPA concentrations, and the response intensify ranked as G0 > T'3/G3 > T3. TBBPA at 1 µg L-1 dosage was detected as the lowest observed effect concentration in multi-biomarkers. The underlying mechanism of aging phenotypes was that reactive oxygen species accumulation led to cell apoptosis regulated by gene ape-1, and confirmed catalase enzyme and superoxide dismutase activity played a crucial role in the detoxification process of TBBPA at the molecular level. This study provided insights into the underlying mechanism of TBBPA-interfered longevity and its environmental multi-generational potential risks.

Remediation of PAHs contaminated industrial soils by hypochlorous acid: performance and mechanisms.

Polycyclic aromatic hydrocarbons (PAHs) mainly originate from incomplete combustion of organic substances and are carcinogenic, mutagenic and teratogenetic, posing a high risk to the ecosystem and human health. The remediation of soils contaminated with PAHs has aroused wide public concern. In this study, hypochlorous acid (HOCl) was applied to realize PAHs removal from industrial contaminated soil with an extremely high degradation efficiency of 93.33% when the initial chlorine concentration was 5000 mg L-1. The degradation behavior of PAHs by HOCl oxidation was investigated in detail. Parameters including chlorine dosage, pH and temperature that had effects on the degradation process were evaluated systematically. The removal of PAHs was followed well with the pseudo-first-order kinetic model. It is found that HOCl and OH˙ were major contributors to the degradation products of chlorinated and oxygenated PAHs. This research provided an easy-operating and energy-saving way to realize the remediation of PAHs contaminated industrial soil practically with high efficiency.

Identification of LuxR Family Regulators That Integrate Into Quorum Sensing Circuit in Vibrio parahaemolyticus.

Vibrio parahaemolyticus is one of the most important food-borne pathogens that cause economic and public health problems worldwide. Quorum sensing (QS) is a way for the cell-cell communication between bacteria that controls a wide spectrum of processes and phenotypic behaviors. In this study, we performed a systematic research of LuxR family regulators in V. parahaemolyticus and found that they influence the bacterial growth and biofilm formation. We then established a QS reporter plasmid based on bioluminescence luxCDABE operon of Vibrio harveyi and demonstrated that several LuxR family regulators integrated into QS circuit in V. parahaemolyticus. Thereinto, a novel LuxR family regulator, named RobA, was identified as a global regulator by RNA-sequencing analyses, which affected the transcription of 515 genes in V. parahaemolyticus. Subsequent studies confirmed that RobA regulated the expression of the exopolysaccharides (EPS) synthesis cluster and thus controlled the biofilm formation. In addition, bioluminescence reporter assays showed that RobA plays a key role in the QS circuit by regulating the expression of opaR, aphA, cpsQ-mfpABC, cpsS, and scrO. We further demonstrated that the regulation of RobA to EPS and MfpABC depended on OpaR and CpsQ, which combined the QS signal with bis-(3'-5')-cyclic dimeric GMP to construct a complex regulatory network of biofilm formation. Our data provided new insights into the bacterial QS mechanisms and biofilm formation in V. parahaemolyticus.

[Distribution and Ecological Risk of Heavy Metals in the Soil of Redevelopment Industrial Sites].

Fifty typical redevelopment industrial sites in the Putuo, Baoshan, Minhang, and Jiangding districts of Shanghai were chosen to evaluate the ecological risk of heavy metals in the soil. The contents of heavy metal (Hg, Cd, Pb, Cr, and As) in 1847 soil samples, taken from vertical sections, were determined, and their risks were evaluated using the Nemero composite index and Hakanson potential ecological risk index. The average contents of Hg, Cd, Pb, Cr, and As in topsoil samples were 0.33, 0.37, 74.55, 69.23, and 9.05 mg·kg-1, respectively. The contents of Hg, Cd, and Pb exceeded the soil background values of Shanghai, which were 2.75, 2.85, and 2.93 times the background values, respectively. The contents of five heavy metals in soil decreased gradually with increased depth. The contents of heavy metals in deep and saturated soils were close to, or below, the background values, indicating that the anthropic activity disturbance was mainly confined to the topsoil. The accumulation of Hg, Cd, and Pb was the most obvious in Putuo topsoil, with the average contents being 4.25, 4.85, and 3.09 times the background values, respectively. The average contents of Hg and Pb in Baoshan were 4.92 and 6.43 times the background values, respectively. The Nemero Composite Index of Baoshan and Putuo districts were 3.70 and 3.20, respectively, representing heavy pollution level at these sites. The Hakanson potential ecological risk indexes of the Putuo and Baoshang districts were 398.59 and 303.08, respectively, with considerable ecological risk levels. The content and ecological risk of heavy metals at the Minhang and Jiading sites were relatively low. In summary, the pollution of heavy metal in the redeveloped industrial sites is influenced by the operating time, industry type, and past management level of the enterprises. The heavy metal accumulation in the Putuo and Baoshan districts, whose industries developed earlier, were higher than those in the Minhang and Jiading districts. The pollution of heavy metal Hg, Cd, and Pb in soil should be a focus of future work.

Ecotoxicity assessment of sodium dimethyldithiocarbamate and its micro-sized metal chelates in Caenorhabditis elegans.

Sodium dimethyldithiocarbamate (SDDC) is a widely used heavy metal chelating agent in harmless treatment of wastewater and hazardous waste, but SDDC and its heavy metal chelates may leak into the environment and bring potential ecological risks. In this study, the model organism Caenorhabditis elegans was used to evaluate the toxic effect of SDDC and its heavy metal Cu, Pb chelates. Multiple endpoints were investigated by subacute exposure to SDDC (0.01-100 mg/L) and micro-sized Cu, Pb chelates of SDDC (1-100 mg/L). Our data indicated that the LC50 value of SDDC was 139.39 mg/L (95% Cl: 111.03, 174.75 mg/L). In addition, SDDC was found that concentration of 1 mg/L is a safe limit value for nematode C. elegans, and concentration above 1 mg/L caused adverse effects on the survival, growth, locomotion behaviors and reactive oxygen species (ROS) production of exposed nematodes. Furthermore, all tested SDDC-Cu and SDDC-Pb chelates had obviously lower toxic effect than untreated Cu, Pb metals. These two chelates also had a lower toxic effect than SDDC agent due to its more stable structure. Moreover, SDDC-Cu had a higher toxic effect than SDDC-Pb at the same concentration. Thus, our results suggest that SDDC as a kind of chelating agent applied in harmless treatment of heavy metals, the safe addition limit should not be exceeded.

Trans-generational effect of neurotoxicity and related stress response in Caenorhabditis elegans exposed to tetrabromobisphenol A.

Tetrabromobisphenol A (TBBPA), one of the most common brominated flame retardants, has been associated with immunotoxicity, neurotoxicity, and reproductive toxicity. However, little attention has been focused on understanding the trans-generational effects of TBBPA. The present study used the Caenorhabditis elegans (C. elegans) animal model to evaluate the trans-generational effects of neurotoxicity induced by environmentally relevant concentrations of TBBPA (0, 0.1, 1, 10, 100, and 1000 µg/L). Multiple indicators including physiological effects (body length, brood size, head thrashes, body bends, and crawling trajectory), degree of neuronal damage (dopamine, GABAergic, and glutamatergic neurons), oxidative stress-related biochemical indicators (superoxide dismutase [SOD] activity, catalase [CAT] enzyme, malondialdehyde [MDA] production, and reactive oxygen species [ROS] accumulation), and stress-related gene expressions have been evaluated in the exposed parental C. elegans generation (G1) and their progeny (G2) under TBBPA-free conditions. The results showed that TBBPA exposure induced adverse effects on physiological endpoints, among which body bends and head thrashes were the most sensitive ones, detected above 1 µg/L in G1 and 100 µg/L in G2 nematodes, respectively. After contaminant exposure, the three neurons revealed damage related to neurobehavioral endpoints, with no hereditary effects in the progeny. The oxidative stress-related biochemical endpoints demonstrated that when the exposure concentrations were above 1 µg/L in maternal worms, impairment can be detected in both generations, but the progeny recovered at low toxicity concentration (1-100 µg/L). The integrated target gene expression profiles were clearly altered in G1 and G2 worms at concentrations between 1 and 1000 µg/L, and a more significant difference existed in two generations of nematodes at low levels (1-10 µg/L) of TBBPA. Studing trans-generational neurotoxicity and the underlying mechanism can generate a precise evaluation of the environmental risk of TBBPA.

Toxicological assessment and underlying mechanisms of tetrabromobisphenol A exposure on the soil nematode Caenorhabditis elegans.

The widespread use of tetrabromobisphenol A (TBBPA) in industries has resulted in its frequent detection in environmental matrices, and the mechanisms of its associated hazards need further investigation. In this study, the nematode Caenorhabditis elegans (C. elegans) was exposed to environmentally relevant concentrations of TBBPA (0, 0.1, 1, 10, 100, 200 µg/L) to determine its effects. At TBBPA concentrations above 1 µg/L, the number of head thrashes, as the most sensitive physiological indicator, decreased significantly. Using the Illumina HiSeq™ 2000 sequencer, differentially expressed genes (DEGs) were determined, and 52 were down regulated and 105 were up regulated in the 200 µg/L TBBPA treatment group versus the control group. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database analysis demonstrated that dorso-ventral axis formation is related to neurotoxicity; metabolism of xenobiotics by Cytochrome P450 (CYP450) and glutathione-S-transferase (GST) was found to be the vital metabolic mechanisms and were confirmed by quantitative real-time polymerase chain reaction (qRT-PCR). GST was ascribed to the augmentation because mutations in cyp-13A7 were constrained under TBBPA exposure. Additionally, oxidative stress indicators accumulated in a dose-dependent relationship. These results will help understand the molecular basis for TBBPA-induced toxicity in C. elegans and open novel avenues for facilitating the exploration of more efficient strategies against TBBPA toxicity.

Insight into the tolerance, biochemical and antioxidative response in three moss species on exposure to BDE-47 and BDE-209.

Responses of Hypnum plumaeforme, Thuidium cymbifolium, and Plagiomnium cuspidatum to short-term (96 h) BDE-47 and BDE-209(0, 0.005, 0.05, 0.5, and 5 µM, respectively) stress were investigated. Both BDE-47 and BDE-209 increased the lipid peroxidation in the three moss species, malondialdehyde (MDA) content increased with the elevated concentration of contaminants, and followed the order: P. cuspidatum > H. plumaeforme > T. cymbifolium on exposure to different concentrations. BDE-47 and BDE-209 stimulated the superoxide dismutase (SOD) and peroxidase (POD) activity of the three moss species, indicating that they played an important role in preventing oxidative stress. Reactive oxygen species (ROS) accumulation was positively correlated with the level of contaminants. The response of anti-oxidative enzymes to BDE-47 and BDE-209 stress differed among the three species. At 5  µM BDE-47 and BDE-209 treatment, the chlorophyll content of T. cymbifolium was even a little higher than the control group. Proline played an important role for the scavenging of ROS in P. cuspidatum and T. cymbifolium. In summary, BDE-47 was more toxic to the three moss species than BDE-209. P. cuspidatum was the most sensitive and T. cymbifolium was the most tolerant species to BDE-47 and BDE-209 stress. The strong resistance and tolerance of T. cymbifolium, combined with sensitive/moderate anti-oxidative response could elucidate its potential use as bio-indicator in the ecological risk assessment of BDE-47 and BDE-209 contamination.

Efficient novel amphiphilic double shells layer coupled with nanoscale zero-valent composite for the degradation of trichloroethylene.

An efficient novel amphiphilic material composed of core-double shells nanocomposite (CDSN) with nanoscale zero-valent iron (NZVI) as the core and PS100-b-PAA16 as inner shell and chitosan as outmost shell has been synthesized successfully. Its application to remove the trichloroethylene (TCE) in stimulated TCE solution with 7.3 ±â€¯0.3 mg/L dissolved oxygen was investigated. The results showed that CDSN after exposure to air for a month could still remove 92.6% of TCE as compared to 61.5% removal rate of NZVI in 360 min (the gram ratio of material: TCE equals to 10:1), exhibiting the great oxidation resistance performance. Specifically, dynamic research of the total removal divided into adsorption by shell layer and degradation by reducibility of NZVI at a predetermined interval was engaged to understand the complete mass transfer process of TCE. The results revealed that CDSN adsorbed 1.5 to 2 folds time TCE as compared to NZVI in the same initial pH = 8.5 aqueous solution. Importantly, CDSN could sustain fixed reactivity to remove about 94.8% of TCE from the start to end. NZVI exhibited greater removal capacity in first 180 min, but later it lost the reducibility and finial removal rate was 89%. The selective adsorption to protonated CDSN was strengthened to increase the removal of TCE at pH 3.5 while NZVI had a worse removal in pH 3.5 performance than pH 8.5.

Ecotoxicity of Caenorhabditis elegans following a step and repeated chronic exposure to tetrabromobisphenol A.

To better understand the toxicity of tetrabromobisphenol A (TBBPA), its effects on the model nematode Caenorhabditis elegans were investigated. Following a step and repeated chronic exposure from L4-larvae to day-10 adult, physiology endpoints (growth and locomotion behaviors including head thrashes, body bends and pumping rate), biochemical endpoints (reactive oxygen species, superoxide dismutase activity, catalase activity), and molecular stress-related gene expression were tested at environmentally relevant concentrations of TBBPA (0.01-100 µg/L). The results showed that concentrations of TBBPA greater than 10 µg/L, clearly influenced the physiology behaviors (growth and locomotion endpoints). Under repeated exposure, C. elegans exhibited adaptive responses in head thrashes and pumping rate. Compared to toxicity evaluation following repeated chronic exposure, a significantly greater response was induced at the same concentration following a step chronic exposure. Reactive oxygen species production was significantly enhanced following a step and repeated TBBPA exposure at the concentrations of 1 and 10 µg/L, respectively. qRT-PCR showed that ctl-1, ctl-2, ctl-3 and sod-3 expression significantly increased, which was obviously correlated with physiological and biochemical behaviors under both treatment conditions according to Pearson correlation test analysis. sod-3 and ctl-2 mutations were more sensitive than the wild-type N2 under a step chronic TBBPA exposure at a level of 10 µg/L. Thus, chronic exposure to TBBPA induces an oxidative stress response in C. elegans, with ctl-2 and sod-3 playing a vital role in TBBPA-induced toxicity in nematodes.

First near complete mitochondrial genome of large toothed toad, Oreolalax major (Anura: Megophryidae) from southwest China.

In this study, the near complete mitogenome sequence (15,469 bp) of Oreolalax major was determined using polymerase chain reaction (PCR). It includes 13 protein-coding genes (PCGs), 2 ribosomal RNA (rRNA) genes and 19 transfer RNA (tRNA) genes (GenBank accession number KU310894). The features of O. major have one more tRNA gene (tRNAMet ) behind the original one before ND2 which is similar to Leptobrachium boringii. Phylogenetic analyses were based on the concatenated sequences of the 13 protein-encoding genes of O. major and other related species.

Different kinds of persulfate activation with base for the oxidation and mechanism of BDE209 in a spiked soil system.

The feasibility of using base persulfate (PS) and coupled with other activation methods (heat, ultrasonic and Fe2+gluconate) was first explored for the removal of decabromodiphenyl ether (BDE209) in a soil system, and various factors were also investigated. The results showed that the removal of BDE209 followed a pseudo-first-order model. Interestingly, the rate constant (k1) indicated a good power exponential relationship with initial PS (k1=0.018×[PS]00.437, R2=0.983, [PS]0=0.02-0.5M) or BDE209 (k1=0.029×e-0.038×[BDE209]0, R2=0.999, [BDE209]0=10-50mgkg-1) concentration, respectively. Additionally, k1 well fitted the Arrhenius equation at the temperature range of 25 to 55°C, and the calculated activation energy (Ea) approximately was 41.2kJmol-1. The removal efficiency could be enhanced in the presence of ultrasound due to increasing the amount of BDE209 molecules desorbed from soil and organic matters. Finally, nine intermediate products were identified during the heat and base co-activated PS oxidation process, and the possible reaction pathways were further proposed.

Enhanced degradation of BDE209 in spiked soil by ferrous-activated persulfate process with chelating agents.

In order to maintain the quantity of ferrous ions, two eco-friendly chelating agents (CAs), i.e., sodium citrate (Citrate) and sodium gluconate (Glu), have been introduced into a traditional iron activated sodium persulfate (PS) system (Fe2+/PS). The results indicated that the PS/CA/Fe2+ oxidation could be an effective method for BDE209 removal. Effects of the chelating agents, reagents dosage, and pH were evaluated in batch experiments. Glu was observed to be more effective than citrate. In addition, the rate constants (k 1) of BDE209 removal indicated a quadratic curve relationship with initial persulfate concentrations (k 1 = -0.019 × [PS]02 + 0.031 × [PS]0 + 0.007, R 2 = 0.933, [PS]0 = 0.1-1.0 M) and a good linear relationship with initial ferrous contents (k 1 = 0.109 × [Fe2+]0 + 0.002, R 2 = 0.943). Furthermore, as a reducing agent, ascorbic acid (H2A) could enhance the degradation rate of BDE209, which might be because H2A accelerated the transformation process from Fe3+- to Fe2+-gluconate complexes.

Inhibition of intestinal glucose uptake by aporphines and secoaporphines.

The effects of aporphines and secoaporphines on glucose uptake by isolated intestinal brush-border membrane vesicles (BBMV) or basolateral membrane vesicles (BLMV) and glucose absorption during in situ intestinal perfusion were studied. Of the tested compounds, N-allylsecoboldine was the most potent glucose uptake inhibitor, with IC50 values of 159 microM and 121 microM, respectively, for uptake by BBMV and BLMV. While thaliporphine competitively inhibited glucose uptake by both membrane preparations, inhibition by N-allylsecoboldine was competitive using BBMV and noncompetitive using BLMV. In addition, N-allylsecoboldine significantly reduced both glucose absorption during in situ intestinal perfusion and blood glucose levels in the oral glucose tolerance test. The results demonstrate that levels of both aporphines and secoaporphines achievable by oral administration have an inhibitory effect on intestinal glucose uptake and suggest that the hypoglycemic effects of these compounds merit attention.