Small Molecule SHP2 Inhibitor LXQ-217 Affects Lung Cancer Cell Proliferation in Vitro and in Vivo.

BACKGROUND: SHP2 is highly expressed in a variety of cancer and has emerged as a potential target for cancer therapeutic agents. The identification of uncharged pTyr mimics is an important direction for the development of SHP2 orthosteric inhibitors. METHODS: Surface plasmon resonance analysis and cellular thermal shift assay were employed to verify the direct binding of LXQ-217 to SHP2. The inhibitory effect of LXQ-217 was characterized by linear Weaver-Burke enzyme kinetic analysis and BIOVIA Discovery Studio. The inhibition of tumor cell proliferation by LXQ-217 was characterized by cell viability assay, colony formation assays and hoechst 33258 staining. The inhibition of lung cancer proliferation in vivo was studied in nude mice after oral administration of LXQ-217. RESULTS: An electroneutral bromophenol derivative, LXQ-217, was identified as a competitive SHP2 inhibitor. LXQ-217 induced apoptosis and inhibited growth of human pulmonary epithelial cells by affecting the RAS-ERK and PI3 K-AKT signaling pathways. Long-term oral administration of LXQ-217 significantly inhibited the proliferation ability of lung cancer cells in nude mice. Moreover, mice administered LXQ-217 orally at high doses exhibited no mortality or significant changes in vital signs. CONCLUSIONS: Our findings on the uncharged orthosteric inhibitor provide a foundation for further development of a safe and effective anti-lung cancer drug.

Triangle Cl-Ag1 -Cl Sites for Superior Photocatalytic Molecular Oxygen Activation and NO Oxidation of BiOCl.

BiOCl photocatalysis shows great promise for molecular oxygen activation and NO oxidation, but its selective transformation of NO to immobilized nitrate without toxic NO2 emission is still a great challenge, because of uncontrollable reaction intermediates and pathways. In this study, we demonstrate that the introduction of triangle Cl-Ag1 -Cl sites on a Cl-terminated, (001) facet-exposed BiOCl can selectively promote one-electron activation of reactant molecular oxygen to intermediate superoxide radicals (⋅O2 - ), and also shift the adsorption configuration of product NO3 - from the weak monodentate binding mode to a strong bidentate mode to avoid unfavorable photolysis. By simultaneously tuning intermediates and products, the Cl-Ag1 -Cl-landen BiOCl achieved >90 % NO conversion to favorable NO3 - of high selectivity (>97 %) in 10 min under visible light, with the undesired NO2 concentration below 20 ppb. Both the activity and the selectivity of Cl-Ag1 -Cl sites surpass those of BiOCl surface sites (38 % NO conversion, 67 % NO3 - selectivity) or control O-Ag1 -O sites on a benchmark photocatalyst P25 (67 % NO conversion and 87 % NO3 - selectivity). This study develops new single-atom sites for the performance enhancement of semiconductor photocatalysts, and also provides a facile pathway to manipulate the reactive oxygen species production for efficient pollutant removal.

Evaluation of Small Molecule Combinations against Respiratory Syncytial Virus In Vitro.

Respiratory syncytial virus (RSV) is a major pathogen that causes severe lower respiratory tract infection in infants, the elderly and the immunocompromised worldwide. At present no approved specific drugs or vaccines are available to treat this pathogen. Recently, several promising candidates targeting RSV entry and multiplication steps are under investigation. However, it is possible to lead to drug resistance under the long-term treatment. Therapeutic combinations constitute an alternative to prevent resistance and reduce antiviral doses. Therefore, we tested in vitro two-drug combinations of fusion inhibitors (GS5806, Ziresovir and BMS433771) and RNA-dependent RNA polymerase complex (RdRp) inhibitors (ALS8176, RSV604, and Cyclopamine). The statistical program MacSynergy II was employed to determine synergism, additivity or antagonism between drugs. From the result, we found that combinations of ALS8176 and Ziresovir or GS5806 exhibit additive effects against RSV in vitro, with interaction volume of 50 µM2% and 31 µM2% at 95% confidence interval, respectively. On the other hand, all combinations between fusion inhibitors showed antagonistic effects against RSV in vitro, with volume of antagonism ranging from -50 µM2 % to -176 µM2 % at 95% confidence interval. Over all, our results suggest the potentially therapeutic combinations in combating RSV in vitro could be considered for further animal and clinical evaluations.

Age estimation using pulp/enamel volume ratio of impacted mandibular third molars measured on CBCT images in a northern Chinese population.

The present study aims to evaluate the relation between chronological age and the ratio of pulp volume (PV) to enamel volume (EV) of impacted mandibular third molars (IMTMs) by using cone-beam computed tomography (CBCT) images and an improved 3D image segmentation technique. A sample of CBCT images of IMTM was collected from 414 northern Chinese subjects (214 male and 200 female clinical patients) ranging in age from 20 to 65 years. The GrowCut effect image segmentation (GCEIS) module algorithm was used to calculate the PV and EV from CBCT images. The total sample was divided into a training group and validation group in a ratio of 7 to 3. The PV/EV ratio (PEr) in the training sample was used to develop a mathematical formula for age estimation as follows: age = - 5.817-21.726 × Ln PEr (p < 0.0001) (Ln, natural logarithm). The mean absolute error (MAE) and root mean square error (RMSE) were used to determine the precision and accuracy of the mathematical formula in the validation group and all samples. The MAEs in the male, female, and pooled gender samples were 9.223, 7.722, and 8.41, respectively, and the RMSEs in the male, female, and pooled gender samples were 10.76, 9.58, and 9.986, respectively. The precise and accurate results indicate that the PEr of IMTM in CBCT images is a potential index for dental age estimation and is possible to be used in forensic medicine.

[Cloning of galectin-1 gene of Angiostrongylus cantonensis and testing the agglutination property of the galectin-1 protein].

Objective: To clone and express the galectin-1 gene of Angiostrongylus cantonensis, and test the agglutination property of its protein. Methods: The three-dimensional structure of galectin-1 was analyzed with Swiss Model. Total RNA was extracted from male worms of A. cantonensis. Primers were designed for galectin-1 based on its coding region (GenBank Accession No. JN133961.1). RT-PCR was performed, and the PCR products were subcloned to pCold Ⅲ plasmid and transduced into Escherichia coli BL21 strain. The recombinant plasmid was extracted from positive clones on LB plate containing 100 µg/ml Kanamycin, and validated with double digestion, PCR identification and sequencing. The confirmed positive clones of E. coli BL21 with the recombinant plasmid were grown in LB medium containing ampicillin (100 µg/ml, 100 µl). IPTG was added to induce expression of the plasmid. The galectin-1 recombinant protein was purified with Ni-NTA beads, and analyzed with SDS-PAGE and Western blotting using anti-serum of mouse immunized with whole worms of A. cantonensis. The agglutination reaction with red blood cells in fresh blood of ICR mouse was observed for the 10-fold serial dilutions of recombinant proteins (5.55 × 10(-1)-5.55 × 10(-5) ng/µl). Results: The Swiss Model analysis showed that the functional galectin-1 had a non-dimeric form. As was expected, the RT-PCR products had a size of 850 bp. Results of double digestion, PCR and sequencing showed successful construction of the pCold Ⅲ-galectin-1 plasmid. SDS-PAGE revealed expression of soluble recombinant fusion protein with molecular weight of ~36 000. Western blotting showed that the galectin-1 protein was recognized by mouse anti-serum. In addition, the minimun concentration of galectin-1 that showed significant agglutination reactions with mouse red blood cells was 5.55 × 10(-4) ng/µl. Conclusion: The galectin-1 clone can be expressed in the pCold Ⅲ plasmid, and its protein product has agglutination property.

The effect of carbon nanotubes and titanium dioxide incorporated in PDMS on biofilm community composition and subsequent mussel plantigrade settlement.

This study investigated the effect of carbon nanotubes (CNTs) and titanium dioxide (TiO2) incorporated in PDMS on biofilm formation and plantigrade settlement of Mytilus coruscus. TiO2 increased bacterial density, and CNTs also increased bacterial density but reduced diatom density in biofilms after 28 days. Further analysis was conducted between bacterial communities on glass, PDMS, CNTs (0.5 wt%) and TiO2 (7.5 wt%). ANOSIM analysis revealed significant differences (R > 0.9) between seven, 14, 21 and 28 day-old bacterial communities. MiSeq sequencing showed that CNTs and TiO2 impacted the composition of 28 day-old bacterial communities by increasing the abundance of Proteobacteria and decreasing the abundance of Bacteroidetes. The maximum decreased settlement rate in 28 day-old biofilms on CNTs and TiO2 was > 50% in comparison to those on glass and PDMS. Thus, CNTs and TiO2 incorporated in PDMS altered the biomass and community composition of biofilms, and subsequently decreased mussel settlement.

A functional genetic variant in fragile-site gene FATS modulates the risk of breast cancer in triparous women.

BACKGROUND: The fragile-site associated tumor suppressor (FATS, formerly known as C10orf90), a regulator of p53-p21 pathway has been involved in the onset of breast cancer. Recent data support the idea that the crosstalk between FATS and p53 may be of physiological importance for reproduction during evolution. The aim of the current study was to test the hypothesis that FATS genetic polymorphism can influence the risk of breast cancer. METHODS: We conducted population-based studies in two independent cohorts comprising 1 532 cases and 1 573 controls in Tianjin of North China, and 804 cases and 835 controls in Guangzhou of South China, coupled with functional validation methods, to investigate the role of FATS genetic variant in breast cancer risk. RESULTS: We identified a functional variant rs11245007 (905C > T, 262D/N) in fragile-site gene FATS that modulates p53 activation. FATS-262 N exhibited stronger E3 activity to polyubiquitinate p53 than did FATS-262D, leading to the stronger transcriptional activity of p53 and more pronounced stabilization of p53 protein and its activation in response to DNA damage. Case-control studies found that CT or TT genotype was significantly associated with a protective effect on breast cancer risk in women with parity ≥ 3, which was not affected by family history. CONCLUSIONS: Our findings suggest the role of FATS-p53 signaling cascade in suppressing pregnancy-related carcinogenesis and potential application of FATS genotyping in breast cancer prevention.

Characterization of self-generated variants in Pseudoalteromonas lipolytica biofilm with increased antifouling activities.

Pseudoalteromonas is widespread in various marine environments, and most strains can affect invertebrate larval settlement and metamorphosis by forming biofilms. However, the impact and the molecular basis of population diversification occurring in Pseudoalteromonas biofilms are poorly understood. Here, we show that morphological diversification is prevalent in Pseudoalteromonas species during biofilm formation. Two types of genetic variants, wrinkled (frequency of 12±5%) and translucent (frequency of 5±3%), were found in Pseudoalteromonas lipolytica biofilms. The inducing activities of biofilms formed by the two variants on larval settlement and metamorphosis of the mussel Mytilus coruscus were significantly decreased, suggesting strong antifouling activities. Using whole-genome re-sequencing combined with genetic manipulation, two genes were identified to be responsible for the morphology alternations. A nonsense mutation in AT00_08765 led to a wrinkled morphology due to the overproduction of cellulose, whereas a point mutation in AT00_17125 led to a translucent morphology via a reduction in capsular polysaccharide production. Taken together, the results suggest that the microbial behavior on larval settlement and metamorphosis in marine environment could be affected by the self-generated variants generated during the formation of marine biofilms, thereby rendering potential application in biocontrol of marine biofouling.

Acute Endoplasmic Reticulum Stress-Independent Unconventional Splicing of XBP1 mRNA in the Nucleus of Mammalian Cells.

The regulation of expression of X-box-binding protein-1 (XBP1), a transcriptional factor, involves an unconventional mRNA splicing that removes the 26 nucleotides intron. In contrast to the conventional splicing that exclusively takes place in the nucleus, determining the location of unconventional splicing still remains controversial. This study was designed to examine whether the unconventional spicing of XBP1 mRNA could occur in the nucleus and its possible biological relevance. We use RT-PCR reverse transcription system and the expand high fidelity PCR system to detect spliced XBP1 mRNA, and fraction cells to determine the location of the unconventional splicing of XBP1 mRNA. We employ reporter constructs to show the presence of unconventional splicing machinery in mammal cells independently of acute endoplasmic reticulum (ER) stress. Our results reveal the presence of basal unconventional splicing of XBP1 mRNA in the nucleus that also requires inositol-requiring transmembrane kinase and endonuclease 1α (IRE1α) and can occur independently of acute ER stress. Furthermore, we confirm that acute ER stress induces the splicing of XBP1 mRNA predominantly occurring in the cytoplasm, but it also promotes the splicing in the nucleus. The deletion of 5'-nucleotides in XBP1 mRNA significantly increases its basal unconventional splicing, suggesting that the secondary structure of XBP1 mRNA may determine the location of unconventional splicing. These results suggest that the unconventional splicing of XBP1 mRNA can take place in the nucleus and/or cytoplasm, which possibly depends on the elaborate regulation. The acute ER stress-independent unconventional splicing in the nucleus is most likely required for the maintaining of day-to-day folding protein homeostasis.

[Preparation and application of the polyclonal antibody of Toxoplasma gondii autophagy protein 8 (TgAtg8)].

OBJECTIVE: To prepare and evaluate specific-TgAtg8 polyclonal antibody. METHODS: The known Saccharomyces cerevisiae Atg protein sequences were used to identify Toxoplasma gondii homologous protein through bioinformatics analysis. TgAtg8 cDNA was amplified and cloned into prokaryotic expression vector pGEX-6p-1. The constructed pGEX-6p-1-TgAtg8 was transformed into E. coli BL21 cells and induced with IPTG for expression. The expression product was analyzed through SDS-PAGE and Western blotting. The recombinant TgAtg8 protein with an N-terminal glutathione-S transferase tag was used to immunize rabbits and raise specific polyclonal antibody against TgAtg8. Subsequently, the antibody was applied for Western blotting and IFA assay. RESULTS: Recombinant expression plasmid of pGEX-6p-1-TgAtg8 was confirmed correct by restriction enzyme digestion and sequencing. SDS-PAGE and Western blotting analysis showed that the recombinant TgAtg8 protein with the predicted molecular weight (M(r)40000) was expressed highly in E. coli BL21. After immunization, the specific antibodies against TgAtg8 protein were produced. The anti-TgAtg8 polyclonal antibody reacted specifically with TgAtg8 fusion protein or endogenous TgAtg8. Importantly, IFA assay determined that the TgAtg8 signal was generally distributed throughout the cytoplasm of the tachyzoites. However, the green fluorescence signal gathered into one or more green spots after induction of autophagy. CONCLUSION: The specific polyclonal antibody against TgAtg8 could be used to observe the dynamics of autophagosome formation in T. gondii, which is useful tool to investigate the autophagic machinery in this parasite.

[Preparation and antigenicity analysis of recombinant aegyptin-like protein of Aedes albopictus].

OBJECTIVE: To clone and express the aegyptin-like protein (alALP) encoding gene from Aedes albopictus salivary gland, and analyze its antigenicity. METHODS: The homology, secondary structure and antigen peptides of alALP and aegyptin protein (GenBank No. ABF18122.1) was analyzed by bioinformatics software tools. Total RNA was extracted from Ae. albopictus salivary gland. The coding region of alALP (GenBank No. AY826121) was amplified by PCR. RT-PCR product was digested with restriction enzyme and ligated into a pGEX-6P-1 vector. The recombinant pGEX-6P-1-alALP plasmid was transformed into E. coli BL21 and induced by IPTG. The recombinant soluble GST-alALP fusion protein was purified with Glutathione Sepharose 4B. The expression product was analyzed by SDS-PAGE and Western blotting. Mice were immunized each with 60 microg purified GST-alALP at every 2 weeks for 3 times, and mouse anti-GST-alALP serum was prepared. Western blotting assay with mice anti-GST-alALP serum and serum of mice exposed to Ae. albopictus bites was used to analyze its antigenicity. RESULTS: Bioinformatics prediction results showed that alALP and aegyptin had 65.58% homology with a similar secondary structure, and a conservative polypeptide. The product of RT-PCR was 762 bp. The recombinant plasmid pGEX-6P-1-alALP was confirmed by double restriction enzyme digestion, PCR and sequencing. SDS-PAGE and Western blotting analysis showed that the bacteria containing recombinant plasmid pGEX-6p-1-alALP expressed a soluble recombinant fusion protein (M(r) 56 000) after being induced with IPTG. Western blotting analysis revealed that GST-alALP protein was recognized by mouse anti-GST-alALP serum and serum of mice ex- posed to Ae. albopictus bites. CONCLUSION: Mature peptide gene of alALP can be expressed in prokaryotic expression system, and the recombinant protein shows antigenicity.

Design of Selective PARP-1 Inhibitors and Antitumor Studies.

Designing selective PARP-1 inhibitors has become a new strategy for anticancer drug development. By sequence comparison of PARP-1 and PARP-2, we identified a possible selective site (S site) consisting of several different amino acid residues of α-5 helix and D-loop. Targeting this S site, 140 compounds were designed, synthesized, and characterized for their anticancer activities and mechanisms. Compound I16 showed the highest PARP-1 enzyme inhibitory activity (IC50 = 12.38 ± 1.33 nM) and optimal selectivity index over PARP-2 (SI = 155.74). Oral administration of I16 (25 mg/kg) showed high inhibition rates of Hela and SK-OV-3 tumor cell xenograft models, both of which were higher than those of the oral positive drug Olaparib (50 mg/kg). In addition, I16 has an excellent safety profile, without significant toxicity at high oral doses. These findings provide a novel design strategy and chemotype for the development of safe, efficient, and highly selective PARP-1 inhibitors.

Locally Asymmetric BiOBr for Efficient Exciton Dissociation and Selective O2 Activation toward Oxidative Coupling of Amines.

Two-dimensional (2D) layered photocatalysts with highly ordered out-of-plane symmetry usually display robust excitonic effects, thus being ineffective in driving catalytic reactions that necessitate unchained charge carriers. Herein, taking 2D BiOBr as a prototype model, we implement a superficial asymmetric [Br-Bi-O-Bi] stacking in the out-of-plane direction by selectively stripping off the top-layer Br of BiOBr. This local asymmetry disrupts the diagnostic confinement configuration of BiOBr to urge energetic exciton dissociation into charge carriers and further contributes to the emergence of a surface dipole field that powers the subsequent separation of transient electron-hole pairs. Distinct from the symmetric BiOBr, which activates O2 into 1O2 via an exciton-mediated energy transfer, surface asymmetric BiOBr favors selective O2 activation into ·O2- for a broad range of amine-to-imine conversions. Our work here not only presents a paradigm for asymmetric photocatalyst design but also expands the toolkit available for regulating exciton behaviors in semiconductor photocatalytic systems.

Plastic properties affect the composition of prokaryotic and eukaryotic communities and further regulate the ARGs in their surface biofilms.

Plastic wastes are ubiquitous in the offshore and oceans with an increasing quantity, and inevitably, microbial communities colonized the plastics to form biofilms, which have become dispersal vectors for antibiotic resistance genes (ARGs). This study focused on the impact of plastic properties including hardness, wettability, and zeta-potential on the biomass, prokaryotic and eukaryotic communities and ARGs in biofilms formed on specific plastics (polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET)) in an estuarine environment. The results showed that, in comparison to PP, more biomass characterized by more dry weight, chlorophyll a (Chl a) and total organic carbon (TOC) was found in biofilms formed on PE and PET, which may be related to their lower surface wettability. Proteobacteria were the dominant prokaryotic phyla, and they accounted for 53.06%, 81.90%, 37.06%, 76.25%, and 54.27% of the total sequences in biofilms on PE, PP, PET, water and sediment, respectively. Ascomycota were the predominant eukaryotic phyla in biofilms, water, and sediment, and their abundances were elevated in biofilms on PP, which accounted for 34.73%. The biofilms on PP had a higher relative abundance of ARGs (3.13) compared to those on PE (2.59) and PET (0.23). Furthermore, both the plastic-biofilm properties (e.g. dry weight, Chl a, and TOC) and microbial communities (e.g., Fungi and Proteobacteria) may be involved in regulating the abundance of ARGs. Moreover, mobile genetic elements (MGEs) were significantly correlated to both the absolute and relative abundance of ARGs, indicating that MGEs may regulate the migration of ARGs in biofilms. Taken together, this investigation provides the significance of the plastic type, surface properties, and surrounding environments in shaping microbial communities and ARGs in biofilms formed on plastics.

Extraction and quantification of metal-containing nanoparticles in marine shellfish based on single particle inductively coupled plasma-mass spectrometry technique.

Quantitative characterization of nanoparticles (NPs) in marine shellfish is critical to understanding the risks of bio-accumulation. Based on single particle (sp)ICP-MS and electron microscopy, a standardized protocol was developed to extract Ag, Au, and indigenous Ti-containing NPs from mussels. The optimal parameters are: dry sample extraction with tetramethylammonium hydroxide (TMAH), 5% (v/v) final concentration of TMAH, extraction at 25 â„ƒ for 12 h, and separation by centrifugation (3000 rpm for 5 min). The particle number recoveries of spiked Ag and Au NPs were 88 ± 0.9% and 95 ± 1.1%, respectively, while Ti-containing NPs had a particle number concentration of 8.2 × 106 particles/mg and an average size of 70 nm in tested mussels. Furthermore, titanium oxide NPs, including rutile, anatase, and Magnéli phases (TixO2x-1) were found ubiquitously in 10 shellfish based on the optimal method. The particle number concentrations and average sizes of the Ti-containing NPs were 2.1 × 106-8.4 × 106 particles/mg and 70-80 nm, respectively. These Ti-containing NPs, such as TiO2, accounted for about half of the Ti mass in shellfish, indicating that marine shellfish may be a significant sink for Ti-containing NPs.

Effects of brucine combined with glycyrrhetinic acid or liquiritin on rat hepatic cytochrome P450 activities in vivo.

Abstract: The activities of four CYP450 enzymes (CYP3A, 1A2, 2El and 2C) and the mRNA expression levels of CYP1A2, 2El, 2Cll and 3A1 in rat liver were determined after Wistar rats were orally administered with brucine (BR) at three dosage levels (3, 15 and 60 mg.kg-1 per day) and the high dose of BR combined with glycyrrhetinic acid (GA, 25 mg.kg-1 per day) or liquiritin (LQ, 20 mg.kg-1 per day) for 7 consecutive days. Compared with the control, brucine caused 24.5% and 34.6% decrease of CYP3A-associated testosterone 6beta-hydroxylation (6betaTesto-OH) and CYP2C-associated tolbutamide hydroxylation (Tol-OH), respectively, and 146.1% increase of CYP2El-associated para-nitrophenol hydroxylation (PNP-OH) at the high dose level. On the other hand, (BR+GA) caused 51.4% and 33.5% decrease, respectively, of CYP2El-associated PNP-OH and CYP1A2-associated ethoxyresorufin-O-de-ethylation (EROD) as compared with the high dose of BR group. Meanwhile, (BR+LQ) caused 41.1% decrease of CYP2El-associated PNP-OH and 37.7% increase of CYP2C-associated Tol-OH. The results indicated that the co-administration of BR with GA or LQ had effect on mRNA expression and activities of the CYP450 enzymes mentioned above to some extent, and the in vivo antagonism of LQ on BR-induced CYPs adverse effects and the in vivo inhibitory action of GA on CYP2E1 and 1A2 might play an important role in the detoxification of Radix Glycyrrhizae against Strychnos nux-vomica L.

Human activities can drive sulfate-reducing bacteria community in Chinese intertidal sediments by affecting metal distribution.

Sulfate-reducing bacteria (SRB), which are ubiquitous in intertidal sediments, play an important role in global sulfur and carbon cycles, and in the bioremediation of toxic metalloids/metals. Pollution from human activities is now a major challenge to the sustainable development of the intertidal zone, but little is known about how and to what extent various anthropic and/or natural factors affect the SRB community. In the current study, based on the dsrB gene, we investigated the SRB community in intertidal sediment along China's coastline. The results showed that dsrB gene abundances varied among different sampling sites, with the highest average abundance of SRB at XHR (near the Bohai Sea). The SRB community structures showed obvious spatial distribution patterns with latitude along the coastal areas of China, with Desulfobulbus generally being the dominant genus. Correlation analysis and redundancy discriminant analysis revealed that total organic carbon (TOC) and pH were significantly correlated with the richness of the SRB community, and salinity, pH, sulfate and climatic parameters could be the important natural factors influencing the composition of the SRB community. Moreover, metals, especially bioavailable metals, could regulate the diversity and composition of the SRB communities. Importantly, according to structural equation model (SEM) analysis, anthropic factors (e.g., population, economy and industrial activities) could drive SRB community diversity directly or by significantly affecting the concentrations of metals. This study provides the first comprehensive investigation of the direct and indirect anthropic factors on the SRB community in intertidal sediments on a continental scale.

Antibiotic resistance genes in biofilms on plastic wastes in an estuarine environment.

Plastic wastes are ubiquitous in aquatic environment. Biofilms, which are often formed on the surface of plastic waste, may contain antibiotic resistance genes (ARGs). This study focused on the occurrence and distribution of ARGs, metal resistance genes (MRGs) and their associated microbial communities in biofilms formed on different types of plastic, in comparison to associated sediment and water samples taken from the Yangtze Estuary. The results showed that polypropylene (PP) and polyethylene (PE) with visible biofilms were highly abundant, and the average absolute abundance of most tested ARGs in the biofilms was higher than that in the sediment and water, indicating that biofilms on plastics can act as a reservoir for ARGs. Moreover, the biofilms on PE had a higher relative abundance of ARGs, compared to those on other plastics, and Firmicutes on PE may be potential hosts for these ARGs. Furthermore, Bacillus, Mycobacterium and Pseudomonas may be multi-resistance genera on plastics, and tetA and tetW may have more potential hosts on PET and PP. Metals, total phosphorus and salinity may be the major environmental factors regulating ARGs in biofilms formed on plastics. The results provide new insights into evaluating the risks caused by plastic wastes and ARGs in biofilms formed on plastics in estuarine environment.

Antibiotic resistance genes in sediments of the Yangtze Estuary: From 2007 to 2019.

To better understand the occurrence and succession of antibiotic resistance genes (ARGs) in the environment, the investigation of ARGs in sediment for a long time scale is urgently needed. In this study, sediment samples were taken in the Yangtze Estuarine area from 2007 to 2019, and the interannual variations in ARGs and their possible physicochemical and socioeconomic influencing factors were analyzed. The results showed that the abundance of ARGs, including sul1, sul2, tetM, tetW, aac(6')-Ib and qnrS, was higher in recent years (from 2015 to 2019) than that in earlier years (from 2007 to 2011), and heavier ARG pollution was found in Wusongkou (WSK) samples than in Liuhekou (LHK) samples. According to the redundancy discriminant analysis (RDA) and correlation analysis, the antibiotics (especially individual antibiotic categories, including oxytetracycline, doxycycline hyclate and norfloxacin), metals and a metal resistance gene (zntA) and total organic carbon (TOC) showed significant correlations to ARGs. In addition, antibiotics, metals, TOC and ARGs were also significantly correlated with several socioeconomic indices. Furthermore, the extended STIRPAT model analysis revealed that the second industry product and the first industry product were the major socioeconomic driver factors for the ARG distribution at WSK and LHK, respectively. Overall, with socioeconomic development, antibiotics, metals, TOC and ARGs increased in sediment. In addition, antibiotics, metals and TOC may participate in the regulation of the occurrence and distribution of ARGs in the Yangtze Estuary for the long time scale.

Time-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 Zn2+, Zn2+ 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 Zn2+ 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.