Preferential Degradation Research Articles

Indigenous functional microbial communities for the preferential degradation of chloroacetamide herbicide S-enantiomers in soil

This study investigated indigenous functional microbial communities associated with the degradation of chloroacetamide herbicides acetochlor (ACE), S-metolachlor (S-MET) and their enantiomers in repeatedly treated soils. The results showed that biodegradation was the main process for the degradation of ACE, S-MET and their enantiomers. Eight dominant bacterial genera associated with the degradation were found: Amycolatopsis, Saccharomonospora, Mycoplasma, Myroides, Mycobacterium, Burkholderia, Afipia, and Kribbella. The S-enantiomers of ACE and S-MET were preferentially degraded, which mainly relied on Amycolatopsis, Saccharomonospora and Kribbella for the ACE S-enantiomer and Amycolatopsis and Saccharomonospora for the S-MET S-enantiomer. Importantly, the relative abundances of Amycolatopsis and Saccharomonospora increased by 146.3%–4467.2% in the S-enantiomer treatments of ACE and S-MET compared with the control, which were significantly higher than that in the corresponding R-enantiomer treatments (25.3%–4168.2%). Both metagenomic and qPCR analyses demonstrated that four genes, ppah, alkb, benA, and p450, were the dominant biodegradation genes (BDGs) potentially involved in the preferential degradation of the S-enantiomers of ACE and S-MET. Furthermore, network analysis suggested that Amycolatopsis, Saccharomonospora, Mycoplasma, Myroides, and Mycobacterium were the potential hosts of these four BDGs. Our findings indicated that Amycolatopsis and Saccharomonospora might play pivotal roles in the preferential degradation of the S-enantiomers of ACE and S-MET.

Molecular fingerprints in shales from the Sanhu biogenic gas fields in eastern Qaidam Basin, NW China: Evidence of biodegradation of shale organic matter

This study provides evidence for hopane and sterane biodegradation in shale organic matter (OM) via geochemical characterization of shale extracts from the biogenic gas fields of the Sanhu Depression in eastern Qaidam Basin, NW China. Nineteen immature source rock cores of the upper Pliocene–Quaternary from the study area are divided into two groups based on distinct results of Rock-Eval analysis and molecular fingerprints. Organic-rich group A shales are dominated by the ααα 20R configurations of steranes, diagenetic hopanoids and are lean in the αββ 20S configurations of steranes, C27–C29 diasteranes, C21–C22 pregnanes and C19–C29 tricyclic terpanes. In contrast, organic-poor and sandy shales of group B have much higher hopane and sterane isomerization ratios, higher C21–C22 pregnanes, C27–C29 diasteranes and C19–C29 tricyclic terpanes but diminished diagenetic hopanoids. C29 5α-sterane and C31 αβ-hopane isomer concentrations and isomerization ratios reveal a depth-controlled diagenetic profile in group A samples whereas they are randomly or inversely distributed in group B. Moreover, the C27–C30 25-norhopane series has been identified in group B core extracts but are absent in group A. These differences are mainly ascribed to biodegradation of group B core OM. Regardless of microbial alteration of hopanes and steranes in the shale extracts, no significant biodegradation of n-alkanes has been observed in the extracts of both shale groups. However, instead of reflecting preferential degradation of biomarkers, this difference is caused by lower microbial availability of n-alkanes than the biomarkers in the special pore structure of fine-grained sediments and dilution of biodegraded n-alkane patterns by the newly generated n-alkanes from the shale OM. The rare occurrence of hopane and sterane biodegradation in fine sediments in the Sanhu Depression is ascribed to the low hydrocarbon yields from organic lean group B cores that failed to alter the biodegradation signature, since no similar biodegradation case has been reported in organic-rich biogenic gas source rock systems worldwide. Due to a self-sourced biogenic gas system consisting of frequently interbedded shales and silts/sands, the Sanhu biogenic gases form predominantly in the more porous and permeable rocks represented by group B but with most energy sources for microbial metabolism diffused from adjacent, organic-rich shales represented by group A.

Earthworms accelerated the degradation of the highly toxic acetochlor S-enantiomer by stimulating soil microbiota in repeatedly treated soils

This study investigated the effects of earthworms on the enantioselective degradation of chloroacetamide herbicide acetochlor with soil microorganisms in repeatedly treated soils. The S-enantiomer degraded more slowly and exerted stronger inhibition on soil microbial functions than the R-enantiomer in single soil system. A synergistic effect was observed between soil microorganisms and earthworms that accelerated the degradation of both the enantiomers, particularly the highly toxic S-enantiomer, which resulted in the preferential degradation of S-enantiomer in soil-earthworm system. Earthworms stimulated five potential indigenous degraders (i.e. Lysobacter, Kaistobacter, Flavobacterium, Arenimonas, and Aquicell), induced two new potential degraders (i.e. Aeromonas and Algoriphagus), and also significantly strengthened the correlations among these seven dominant potential degraders and other microorganisms. Notably, the relative abundances of Flavobacterium and Aeromonas in soil treated with earthworms for S-enantiomer were higher than those for R-enantiomer. Furthermore, earthworms significantly stimulated overall soil microbial activity and improved three microbial metabolic pathways, and xenobiotics biodegradation and metabolism, signal transduction, cell motility, particularly for the S-enantiomer treatment with earthworms, which alleviated the strong inhibition of S-enantiomer on microbial community functions. This study confirmed that earthworms accelerated the degradation of the highly toxic acetochlor S-enantiomer in soil, providing a potential approach in chloroacetamide herbicide-polluted soil remediation.

Investigations by AFM of Ageing Mechanisms in PLA-Flax Fibre Composites during Garden Composting.

PLA-flax non-woven composites are promising materials, coupling high performance and possible degradation at their end of life. To explore their ageing mechanisms during garden composting, microstructural investigations were carried out through scanning electron microscopy (SEM) and atomic force microscopy (AFM). We observe that flax fibres preferentially degrade ‘inwards’ from the edge to the core of the composite. In addition, progressive erosion of the cell walls occurs within the fibres themselves, ‘outwards’ from the central lumen to the periphery primary wall. This preferential degradation is reflected in the decrease in indentation modulus from around 23 GPa for fibres located in the preserved core of the composite to 3–4 GPa for the remaining outer-most cell wall crowns located at the edge of the sample that is in contact with the compost. Ageing of the PLA matrix is less drastic with a relatively stable indentation modulus. Nevertheless, a change in the PLA morphology, a significant decrease in its roughness and increase of porosity, can be observed towards the edge of the sample, in comparison to the core. This work highlights the important role of intrinsic fibre porosity, called lumen, which is suspected to be a major variable of the compost ageing process, providing pathways of entry for moisture and microorganisms that are involved in cell wall degradation.

Biodegradation of binary mixtures of octane with benzene, toluene, ethylbenzene or xylene (BTEX): insights on the potential of Burkholderia, Pseudomonas and Cupriavidus isolates

The contamination of the environment by crude oil and its by-products, mainly composed of aliphatic and aromatic hydrocarbons, is a widespread problem. Biodegradation by bacteria is one of the processes responsible for the removal of these pollutants. This study was conducted to determine the abilities of Burkholderia sp. B5, Cupriavidus sp. B1, Pseudomonas sp. T1, and another Cupriavidus sp. X5 to degrade binary mixtures of octane (representing aliphatic hydrocarbons) with benzene, toluene, ethylbenzene, or xylene (BTEX as aromatic hydrocarbons) at a final concentration of 100ppm under aerobic conditions. These strains were isolated from an enriched bacterial consortium (Yabase or Y consortium) that prefer to degrade aromatic hydrocarbon over aliphatic hydrocarbons. We found that B5 degraded all BTEX compounds more rapidly than octane. In contrast, B1, T1 and X5 utilized more of octane over BTX compounds. B5 also preferred to use benzene over octane with varying concentrations of up to 200mg/l. B5 possesses alkane hydroxylase (alkB) and catechol 2,3-dioxygenase (C23D) genes, which are responsible for the degradation of alkanes and aromatic hydrocarbons, respectively. This study strongly supports our notion that Burkholderia played a key role in the preferential degradation of aromatic hydrocarbons over aliphatic hydrocarbons in the previously characterized Y consortium. The preferential degradation of more toxic aromatic hydrocarbons over aliphatics is crucial in risk-based bioremediation.

Enzymatic degradability and release properties of graphene oxide/silk fibroin nanocomposite films

AbstractThe structure evolution of silk fibroin (SF) in the nanocomposite films with graphene oxide (GO) was investigated and related to the enzymatic degradability and release property. The interaction with GO was found to induce conformation transition of SF from random coil to β‐sheet. However, the surface binding constrained the rearrangement of the silk chains, leading to a decrease of β‐sheet when GO content was more than 1.0%. The crystal structure of SF played a key role in the degradation of GO/SF composites. The preferential degradation of the hydrophilic blocks resulted in a faster degradation of SF films with higher β‐sheet content. The addition of GO to SF matrix led to a slower release and a reduction of the burst release of RhB, the model compound. The release profile was well fitted to the Rigter–Peppas equation, from which the characteristic constant decreased and the diffusional exponent increased with increasing GO content but quickly leveled off when GO content was more than 1.0%. Degradation of the composites had little influence on the characteristic constant of RhB release, however, led to an increased diffusional exponent, which was more evident for the composites with higher β‐sheet content.

Molecular-structure evolution during in vitro fermentation of granular high-amylose wheat starch is different to in vitro digestion

This study investigates the evolution of the distributions of whole molecular size and of chain length of granular wheat starches (37 ~ 93% amylose content), subjected to in vitro fermentation with a porcine faecal inoculum or digestion with pancreatic enzymes. The results showed that the molecular structures of high-amylose starch (HAS) unfermented residues largely remained unchanged during the fermentation process, while wild-type starch (37% amylose content) showed a preferential degradation of the amylopectin fraction. In contrast, under simulated digestion conditions, the undigested residues of HAS showed structural changes, including a decrease in amylose content, a shift of amylose peak position towards lower degrees of polymerisation, and an enzyme-resistant fraction. These changes of starch structure are likely to be dependent on the different starch-degrading enzyme activities present in pancreatic vs. microbial systems. Molecular changes in response to fermentation metabolism revealed by size-exclusion chromatography can help understand the microbial utilization of resistant starch.

The CDC37-HSP90 chaperone complex co-translationally degrades the nascent kinase-dead mutant of HIPK2.

Homeodomain-interacting protein kinase 2 (HIPK2) is a highly conserved, constitutively active Ser/Thr protein kinase that is involved in various important biological processes. HIPK2 activates itself by auto-phosphorylation during its synthesis, and its activity is mainly controlled through modulation of its expression by ubiquitin-dependent degradation. By comparing the expression of wild-type and kinase-defective HIPK2, we have recently described a novel mechanism of HIPK2 regulation that is based on preferential co-translational degradation of kinase-defective versus wild-type HIPK2. Here, we have addressed this novel regulatory mechanism in more detail by focusing on the possible involvement of chaperones. Our work shows that HIPK2 is a client of the CDC37-HSP90 chaperone complex and points to a novel role of CDC37 in the co-translational degradation of a client protein.

Bromodomain protein BRDT directs \u0394Np63 function and super-enhancer activity in a subset of esophageal squamous cell carcinomas

Esophageal squamous cell carcinoma (ESCC) is the predominant subtype of esophageal cancer with a particularly high prevalence in certain geographical regions and a poor prognosis with a 5-year survival rate of 15–25%. Despite numerous studies characterizing the genetic and transcriptomic landscape of ESCC, there are currently no effective targeted therapies. In this study, we used an unbiased screening approach to uncover novel molecular precision oncology targets for ESCC and identified the bromodomain and extraterminal (BET) family member bromodomain testis-specific protein (BRDT) to be uniquely expressed in a subgroup of ESCC. Experimental studies revealed that BRDT expression promotes migration but is dispensable for cell proliferation. Further mechanistic insight was gained through transcriptome analyses, which revealed that BRDT controls the expression of a subset of ΔNp63 target genes. Epigenome and genome-wide occupancy studies, combined with genome-wide chromatin interaction studies, revealed that BRDT colocalizes and interacts with ΔNp63 to drive a unique transcriptional program and modulate cell phenotype. Our data demonstrate that these genomic regions are enriched for super-enhancers that loop to critical ΔNp63 target genes related to the squamous phenotype such as KRT14, FAT2, and PTHLH. Interestingly, BET proteolysis-targeting chimera, MZ1, reversed the activation of these genes. Importantly, we observed a preferential degradation of BRDT by MZ1 compared with BRD2, BRD3, and BRD4. Taken together, these findings reveal a previously unknown function of BRDT in ESCC and provide a proof-of-concept that BRDT may represent a novel therapeutic target in cancer.

Long-term changes in land use influence phosphorus concentrations, speciation, and cycling within subtropical soils

While land conversion from native vegetation to agriculture influences the concentration, speciation, and cycling of soil phosphorus (P), the nature of these changes remain poorly understood. We collected surface soils (0–10 cm) from paired sites at three locations, comparing soil from native vegetation with adjacent soils converted for cropping, pasture, and plantation for up to 115 y. The extent of organic P loss upon land use change differed between the three soils, with conversion to cropping causing the largest decreased in soil organic P as well as phosphatase activity. Using solution 31P nuclear magnetic resonance (NMR), it was found that cropping caused a pronounced decrease in organic P – both orthophosphate monoesters and orthophosphate diesters. Furthermore, cropping soils had a substantial reduction in the diester-P/monoester-P ratio, indicating the preferential degradation of the more labile orthophosphate diester-P upon conversion to cropping. Importantly, by subsequently converting cropping land to pasture or plantation, these adverse P-related changes could be reversed or at least halted. Synchrotron-based X-ray absorption near-edge structure (XANES) demonstrated that land use change had no pronounced impact on inorganic P, with sorbed P dominating in all treatments. Changes in land use also influenced bacterial diversity, with land use change effects being specific to the three soils. This study provides information on how land use changes alters P behaviour and cycling in soils, with this being important for ensuring the sustainable use of soils for food production.

Spatial heterogeneity in fatty acid abundance and composition across surface sediments of Lake Taihu, Eastern China: Implications for the use of lipids in evaluating carbon cycling and burial in lake systems

Fatty acids (FAs) present in the surface sediments of Lake Taihu were analyzed for spatial heterogeneity in abundance and composition in order to test the suitability of these lipids to indicate variation in sources and preservation status of organic matter (OM) in sediments. The results indicate that terrestrial plant-derived FAs were relatively enriched in Meiliang and Zhushan Bays, the most eutrophic regions of Lake Taihu, while FAs of phytoplankton origin were relatively low. This unexpected result might reflect a preferential degradation of phytoplankton OM and phytoplankton-derived FAs. Furthermore, massive inputs of refractory terrestrial OM could significantly dilute concentrations of phytoplankton FAs. In sediments from East Bay, phytoplankton-derived FAs were more abundant than in Zhushan Bay, although this region had the lowest levels of nutrients and the lowest phytoplankton productivity. This result was attributed to a greatly enhanced preservation of labile FAs, probably caused by reduced sediment resuspension in this region with dense growth of submerged macrophytes. Phytoplankton productivity and terrestrial OM inputs were moderate in Central Region, but abundances of all FAs and ratios of C16:1/n-C16, C18:1/n-C18 and C18:1ω7/C18:1ω9 both reached their lowest in sediments from this region, possibly as a result of significant degradation of FAs driven by strong sediment resuspension. Sediments from Gonghu Bay and Southern Region were relatively enriched in phytoplankton FAs, and this was ascribed to low inputs of terrestrial OM, which limited the dilution effect. In contrast to FAs, short-chain n-alkane abundances provided an accurate indication of variation in phytoplankton input.

Role of Metal Vacancies in the Mechanism of Thermal Degradation of InGaN Quantum Wells.

In this work, we study the thermal degradation of In-rich InxGa1-xN quantum wells (QWs) and propose explanation of its origin based on the diffusion of metal vacancies. The structural transformation of the InxGa1-xN QWs is initiated by the formation of small initial voids created due to agglomeration of metal vacancies diffusing from the layers beneath the QW. The presence of voids in the QW relaxes the mismatch stress in the vicinity of the void and drives In atoms to diffuse to the relaxed void surroundings. The void walls enriched in In atoms are prone for thermal decomposition, what leads to a subsequent disintegration of the surrounding lattice. The phases observed in the degraded areas of QWs contain voids partly filled with crystalline In and amorphous material, surrounded by the rim of high In-content InxGa1-xN or pure InN; the remaining QW between the voids contains residual amount of In. In the case of the InxGa1-xN QWs deposited on the GaN layer doped to n-type or on unintentionally doped GaN, we observe a preferential degradation of the first grown QW, while doping of the underlying GaN layer with Mg prevents the degradation of the closest InxGa1-xN QW. The reduction in the metal vacancy concentration in the InxGa1-xN QWs and their surroundings is crucial for making them more resistant to thermal degradation.

Physicochemical and structural characteristics of sorghum starch as affected by acid‐ethanol hydrolysis

Acid alcohol hydrolysis of starch is a sustainable chemical method and versatile tool to control molecular weight. Sorghum starch was acid hydrolyzed in ethanol for durations ranging from 24 to 240 h. The native and acid ethanol treated (AET) starches were investigated for their physicochemical, thermal, structural and pasting characteristics. Native starch showed degree of polymerization of 2624 anhydrous glucose units (AGU), amylose content of 26%, swelling power and solubility of 12.2 g/g and 5%, respectively. AET starches showed significantly (p < 0.05) higher solubility (19.8–58.4%) whereas lower values for swelling power (4.3–11 g/g), were observed. The chain length profiles of debranched native and AET sorghum starches, as obtained from high-performance size-exclusion chromatography (HPSEC), indicated preferential degradation of amylose and amylopectin long chains. This led to decrease in intrinsic and pasting viscosities for AET starches. Comparison of X-ray diffractograms (XRD) of native and AET treated sorghum starches showed that there is no change in the diffraction pattern (‘A’ type) upon treatment however the relative crystallinity was observed to decrease upon hydrolysis. Granule structure remained intact however, with AET birefringence loss in some granules was observed, which indicated change in radial orientation of double helices and chain mobility at granule centre. The results indicated that sorghum starch can be tailored by AET and could be used in the food industry for various food formulations.

Impact of selective degradation on molecular isotope compositions in oxic and anoxic marine sediments

One of the central assumptions of paleoenvironmental research using lipid biomarker isotope compositions in sedimentary archives is the isotopic stability of these compounds after deposition. If this indeed applies for open marine sediments with low sedimentation rates and strong biodegradation is, however, not well constrained. Here we study lipid biomarker isotope compositions from two sediment cores from the brine-filled Shaban Deep in the northern Red Sea that receive comparable water column flux due to close geographic proximity but are deposited under opposite anoxic (inside the brine) and oxic (outside the brine) sedimentary conditions. Despite almost complete degradation of some compounds in the oxic sediments, we show that the stable carbon isotope compositions of long-chain n-alkanes, alkenones and bulk organic matter (OM) remain stable among the two cores. The relative distribution of long-chain n-alkanes and alkenones is also preserved. Conversely, the stable hydrogen isotope composition of long-chain n-alkanes and bulk OM increases consistently during degradation (10‰ vs VSMOW for n-alkanes and 40‰ for of bulk OM) indicating the preferential degradation of labile bulk OM and n-alkane fractions that are isotopically lighter. For long-chain fatty acids we find shifts in relative distribution and variability of stable hydrogen and carbon isotope compositions indicating an overall marine sourcing of these compounds that contrasts their usual interpretation as plant derived markers. We conclude that isotope compositions of source-specific refractory molecules show only minor variations under strong degradation, while compounds with multiple sources can show strong variability potentially impeding their use as paleoenvironmental proxies.

Choreography of multiple omics reveals the mechanism of lipid turnover in Schizochytrium sp. S31

Lipid turnover in Schizochytrium supports a preferential degradation of saturated fatty acids and a reservation of polyunsaturated fatty acids. In this study, multiple omics were utilized at different cultivation stages of Schizochytrium sp. S31 to reveal the mechanism of lipid turnover. During the lipid turnover stage, palmitic acid content decreased from 41.18% to 21.33%, while docosahexaenoic acid content increased from 31.20% to 50.43%. The lipidomic analysis showed that the lipid turnover mainly happened to saturated triacylglycerol accompanying with an increased level of phosphatidylinositol and phosphatidylcholine. The transcriptomic result further indicated that the differential expression genes related to the fatty acid degradation pathway were significantly increased, and the formation of phospholipids from diacylglycerol was enhanced. Finally, genomic sequencing and genetic engineering proved that the characterized triacylglycerol lipase might participate in the preferential hydrolysis of saturated fatty acids during lipid turnover. These results would not only enrich the current knowledge regarding the lipid turnover phenomenon but also contribute to the production of high-quality single cell oil from microalgae.

Bio-Based Poly(butylene furandicarboxylate-co-glycolate) Copolyesters: Synthesis, Properties, and Hydrolysis in Different Aquatic Environments for Water Degradation Application

In an environment of high salinity, low temperature, and the presence of a few bacteria in seawater, improving the non-enzymatic hydrolysis of polyesters is one of the effective methods for developing seawater degradable materials. In this research, poly(butylene furandicarboxylate-co-glycolate) (PBFGA) copolyesters were synthesized via melt polycondensation. The PBFGA copolymer possessed excellent mechanical properties and thermal stability. Its tensile strength was 15–50 MPa and the elongation at break was more than 120% from the tensile tests. GA units improved the flexibility of PBF segments, and the PBFGA copolymer exhibited an amorphous structure. The PBFGA copolymer possessed good hydrolysis properties and the weight loss of PBFGA50 was more than 30% after 84 days of degradation in deionized water. Lipase catalyzed, and the salt inhibited the hydrolysis of the ester bond. PBFGA exhibited a bulk degradation mechanism, and sponge pores were formed on the surface due to preferential degradation of the PGA component, which was conducive to the further degradation of the internal groups. Some butanediol and glycolic acid terminated oligomers were produced during the degradation process, and rearrangement crystallization occurred in the chain segment. Thus, PBFGA copolyesters have the potential to serve as promising seawater degradable materials with excellent tensile and non-enzymatic degradable properties.

Effects of colloidal TiO&lt;sub&gt;2&lt;/sub&gt; particles on photodegradation of dissolved organic matter from different sources: Based on molecular weight difference analysis

溶解性有机质（DOM）广泛存在于多种水环境介质，其光降解过程显著影响水体污染物的化学形态及生态风险.本文以典型陆源天然有机质（NOM）和藻源有机质（AlgOM）为研究对象，采用切向超过滤技术将初始DOM样品（Bulk，<0.45 μm）分为高分子量（HMW，1 kDa~0.45 μm）和低分子量（LMW，<1 kDa）组分，研究胶体TiO₂颗粒存在下不同分子量有机组分的光降解行为差异.表征结果表明，DOM样品的有机质均相对较多地分布在LMW组分中（55.3%~57.8%），但HMW的芳香性比LMW组分高；三维光谱结果表明AlgOM富含类蛋白和类腐殖物质，而NOM只含类腐殖物质；进一步分析发现类蛋白物质主要分布于HMW组分，类腐殖物质则主要分布于LMW组分.胶体颗粒的存在通过吸附作用抑制AlgOM中有机质及芳香性物质的光降解，而通过催化作用促进NOM中有机质及芳香性物质的光降解.胶体颗粒不改变不同分子量DOM中有机质的光降解效率顺序，均为HMW>Bulk>LMW，说明HMW有机质更易光降解.但无胶体颗粒时AlgOM和NOM芳香物质的光降解效率为LMW>Bulk>HMW，且胶体颗粒的存在改变不同分子量NOM芳香性物质的光降解顺序.另外，无胶体颗粒存在时陆源类腐殖物质比藻源类腐殖物质更易光降解，而胶体颗粒的存在均可促进藻源和陆源类腐殖质物质光降解；相比于HMW类腐殖质，LMW类腐殖物质具有较高的光敏性和优先降解特性.;Dissolved organic matter (DOM) exists widely in water environmental media, and its photodegradation process significantly affects the chemical species and ecological risk of pollutants in waters. This study took the typical terrestrial natural organic matter (NOM) and algal-derived organic matter (AlgOM) as the research objects, fractionating the initial DOM sample (Bulk, <0.45 μm) into high molecular weight (HMW, 1 kDa-0.45 μm) and low molecular weight (LMW, <1 kDa) fractions via tangential ultrafiltration technique, to analyze the difference of photodegradation behavior of organic components with different molecular weights in the presence of colloidal TiO₂ particles. The characterization results showed that organic matter of DOM samples was relatively more distributed in LMW components (55.3%-57.8%), but HMW was more aromatic than LMW components. Three-dimensional fluorescence spectrum showed that AlgOM was rich in protein-like and humus-like substances, while NOM only contained humus-like substances. Further analysis revealed that protein-like substances were mainly distributed in HMW components, and humus-like substances were mainly distributed in LMW components. The presence of colloidal particles promoted the photodegradation of organic matter and aromatic substances in NOM by catalytic effect, while inhibited the photodegradation of organic matter and aromatic substances in AlgOM by adsorption effect. Colloidal particles did not change the photodegradation efficiency order of organic matter in DOM with different molecular weights, all of which were HMW>Bulk>LMW, indicating that HMW organic matters were easier to be photodegraded. However, without colloidal particles, the photodegradation efficiency of AlgOM and NOM aromatics was LMW>Bulk>HMW, and the presence of colloidal particles changed the photodegradation order of NOM aromatics with different molecular weights. In addition, terrestrial humus was more easily degraded than algal humus in the absence of colloidal particles, and the presence of colloidal particles promoted the photodegradation of both algal and terrestrial humus. Compared with HMW humus, LMW humus had higher photosensitivity and preferential degradation characteristics.

Substrate specificity of bacterial endoribonuclease toxins

Bacterial endoribonuclease toxins belong to a protein family that inhibits bacterial growth by degrading mRNA or rRNA sequences. The toxin genes are organized in pairs with its cognate antitoxins in the chromosome and thus the activities of the toxins are antagonized by antitoxin proteins or RNAs during active translation. In response to a variety of cellular stresses, the endoribonuclease toxins appear to be released from antitoxin molecules via proteolytic cleavage of antitoxin proteins or preferential degradation of antitoxin RNAs and cleave a diverse range of mRNA or rRNA sequences in a sequence-specific or codon-specific manner, resulting in various biological phenomena such as antibiotic tolerance and persister cell formation. Given that substrate specificity of each endoribonuclease toxin is determined by its structure and the composition of active site residues, we summarize the biology, structure, and substrate specificity of the updated bacterial endoribonuclease toxins.

Preferential and efficient degradation of phenolic pollutants with cooperative hydrogen-bond interactions in photocatalytic process

Phenolic pollutants as highly toxic and hazardous organics are widely generated from industrial and domestic process. Phenolic pollutants with different hydroxyl position (catechol, resorcinol, hydroquinone, phenol) were preferentially and efficiently oxidized in photocatalytic process (PC) by designing boron-doped TiO2 (B–TiO2).The key role for enhancing the photocatalytic activity of B–TiO2 was the formation of abundant Ti3+ species. The formation of Ti3+-O weakened the competitive adsorption of H2O in aqueous solution and favored the formation of cooperative hydrogen bond on the surface of B–TiO2, leading to enhanced adsorption of phenolic pollutants. The degradation rate constant of B–TiO2 (kB-TiO2) was regardless of the corresponding oxidation potential of phenolic pollutants. The kB-TiO2 for catechol in photocatalytic process was as high as 3.46 min−1, which was 18.2, 1.6 times higher than that of biodegradation and ozonation methods, respectively. Of note, the preferential removal mechanism of phenolic pollutants was elucidated by in-situ attenuated total reflectance (ATR)-IR and density functional theory calculation (DFT). The results were helpful for developing new preferential oxidation technologies in HO∙-mediated process for selectively removing low concentration but highly toxic pollutants.

Co-occurrence of antiseptic triclocarban and chiral anti-inflammatory ibuprofen in environment: Association between biological effect in sediment and risk to human health

Residues of antiseptics and drugs have been ubiquitously detected in aquatic water-sediment systems, and are thus considered emerging contaminants that threaten our global environment. To investigate the potential risk of ibuprofen and triclocarban in sediment, effects of enzyme activity on the enantioselective degradation in sediment were investigated. Enantioselective fate of rac-ibuprofen was observed in sediment with R-enantiomer exhibiting preferential degradation. Enzyme evidence showed that high levels of triclocarban could significantly inhibit activities of catalase and urease activities in sediment, as well as increase the half-life of ibuprofen (from 5.8 d to 10.1 d). Cytotoxicity data suggested that cell growth processes were significantly affected by ibuprofen and triclocarban co-exposure, which was consistent with apoptosis results. Additionally, the expression of several proteins (Cyto-c, Nrf2, p62, Keap1, NQO1, and Pink1) were markedly induced upon exposure to ibuprofen in the presence of triclocarban. In conclusion, these findings illustrated that co-occurrence of ibuprofen and triclocarban residues have synergistic adverse effects to the environment and synergistically threaten human health.