Response mechanism of soil leachate and disinfection by-product formation to extreme precipitation events under continuous drought scenario.

In this study, a rainfall simulation device was employed to investigate the response mechanism of soil leachate and disinfection by-products formation potential (DBPsFP) to extreme precipitation events. The results revealed that the aromaticity of dissolved organic matter (DOM) and the concentration of hydrophobic DOM containing aromatic carbon groups in leachate decreased with rising temperature. The humification degree of DOM decreased at 25 °C (99 mm/h), while the humification degree and protein-like level of DOM increased under high temperatures droughts (45 °C and 65 °C). Higher temperatures resulted in the leach of more microbial-derived humus and low molecular phenolic compounds from soil and broadened the range of molecular weight distribution. Increasing temperature increased DBPsFP and DBPs species and caused the precursors of haloacetic acids (HAAs) in leachate to become more hydrophobic, while the precursors of trihalomethanes (THMs) became more hydrophilic. Most importantly, the increased temperature attenuated the rainfall-mediated dilution of organic pollutant concentration, and temperature has a more significant effect than extreme rainfall in DOM abundance and the formation potential (or species) of DBPs. The results help to better understand the impact of climate change on the physicochemical processes of water quality.

Contribution of GalU to biofilm formation, motility, antibiotic and serum resistance, and pathogenicity of Salmonella Typhimurium.

Introduction: Salmonella Typhimurium is the leading cause of foodborne illnesses in China, resulting in major epidemics and economic losses in recent years. Uridine diphosphate-glucose pyrophosphorylase galU plays an important role in thebiosynthesis of the bacterial envelope. Herein, we evaluated the role of galU in S. Typhimurium infection in chicken. Methods: A galU gene mutant was successfully constructed by red homologous recombination technology, and biological characteristics were studied. Results: The galU mutant strain had a rough phenotype;was defective in biofilm formation, autoagglutination, and motility; exhibited greater sensitivity to most antibiotics, serum, and egg albumen; and had lowercapacity for adhesion to chicken embryo fibroblasts cell line (DF-1). The galU mutant showed dramatically attenuated pathogenicity in chicken embryos (100,000-fold), BALB/c mice (420-fold), and chicks (100-fold). Discussion: The results imply that galU is an important virulence factor in the pathogenicity of S. Typhimurium, and it may serve a target for the development of veterinary drugs, providing a theoretical basis for the prevention and control of S. Typhimurium.

Identification of Three Campylobacter Lysins and Enhancement of Their Anti-Escherichia coli Efficacy Using Colicin-Based Translocation and Receptor-Binding Domain Fusion.

The emergence of multidrug-resistant Escherichia coli, which poses a major threat to public health, has motivated the development of numerous alternative antimicrobials. Lysins are bacteriophage- and bacterium-derived peptidoglycan hydrolases that represent a new antibiotic treatment targeting bacterial cell walls. However, the bactericidal effect of native lysins on Gram-negative bacteria is restricted by the presence of an outer membrane. Here, we first evaluated the antibacterial activity of three Campylobacter-derived lysins (Clysins) against E. coli. To improve their transmembrane ability and antibacterial activities, six engineered Clysins were constructed by fusing with the translocation and receptor-binding (TRB) domains from two types of colicins (colicin A [TRBA] and colicin K [TRBK]), and their biological activities were determined. Notably, engineered lysin TRBK-Cly02 exhibited the highest bactericidal activity against the E. coli BL21 strain, with a reduction of 6.22 ± 0.34 log units of cells at a concentration of 60.1 µg/mL, and formed an observable inhibition zone even at a dose of 6.01 µg. Moreover, TRBK-Cly02 killed E. coli dose dependently and exhibited the strongest bactericidal activity at pH 6. It also exhibited potential bioactivity against multidrug-resistant E. coli clinical isolates. In summary, this study identified three lysins from Campylobacter strains against E. coli, and the enhancement of their antibacterial activities by TRB domains fusion may allow them to be developed as potential alternatives to antibiotics. IMPORTANCE Three lysins from Campylobacter, namely, Clysins, were investigated, and their antibacterial activities against E. coli were determined for the first time. To overcome the restriction of the outer membrane of Gram-negative bacteria, we combined the TRB domains of colicins with these Clysins. Moreover, we discovered that the Clysins fused with TRB domains from colicin K (TRBK) killed E. coli more effectively, and this provides a new foundation for the development of novel bioengineered lysins by employing TRBK constructs that target outer membrane receptor/transport systems. One of the designed lysins, TRBK-Cly02, exhibited potent bactericidal efficacy against E. coli strains and may be used for control of multidrug-resistant clinical isolates. The results suggest that TRBK-Cly02 can be considered a potential antibacterial agent against pathogenic E. coli.

Establishing Heterologous Production of Microcins J25 and Y in Bacillus subtilis.

Microcin J25 (MccJ25) and microcin Y (MccY) are lasso peptides and considered potential alternatives to antibiotics and harmful preservatives. The combination of these two microcins can provide a wide antimicrobial spectrum against food-borne Salmonella. Currently, MccJ25 and MccY are produced using Escherichia coli expression systems; however, the entire production process is accompanied by negative effects from endotoxins. In this study, we identified Bacillus subtilis as a suitable host for MccJ25 and MccY production. High-level production of microcins was achieved by promoter optimization, host strain selection, and recombinant expression. The engineered strains produced maximum yields of 2.827 µM MccJ25 and 1.481 µM MccY. This is the first study to demonstrate the expression of MccJ25 and MccY in B. subtilis, and it offers a few engineered strains that are without antibiotic resistance markers, inducer-free, sporulation-deficient, and free of the negative effects of endotoxins for antibacterial therapy and food preservation.

Language impairments in children with developmental language disorder and children with high-functioning autism plus language impairment: Evidence from Chinese negative sentences.

There is controversy as to whether children with developmental language disorder (DLD) and those with high-functioning autism plus language impairment (HFA-LI) share similar language profiles. This study investigated the similarities and differences in the production of Chinese negative sentences by children with DLD and children with HFA-LI to provide evidence relevant to this controversy. The results reflect a general resemblance between the two groups in their lower-than-TDA (typically developing age-matched) performance. Both groups encountered difficulties in using negative markers, which suggests that they might be impaired in feature agreement. Slight differences were detected between the two groups. Specifically, children with DLD experienced difficulties with the agreement on the feature [+telic] and that on the feature [+dynamic], while children with HFA-LI had difficulties with the agreement on the feature [+dynamic] and that on the feature [-dynamic]. This study supports the idea of a common symptomatology for the two disorders. More importantly, it suggests that these two disorders, DLD and HFA-LI, are not altogether the same in terms of language impairment. This paper concludes that general labels should not be simply attached to any children with language disorders. Instead, atypical language is very worthy of further analysis in the categorization of language disorders.

Use of Aspect Markers by Mandarin-speaking Children with High-Functioning Autism Plus Language Impairment and Children with Developmental Language Disorder.

INTRODUCTION: This study investigates the comprehension and production of four typical Mandarin aspect markers zai-, -le, -zhe, and -guo by preschool children with high functioning autism plus language impairment (HFA-LI) and those with developmental language disorder (DLD), by comparing them with typically developing age-matched (TDA) children. METHODS: Twenty children with HFA-LI (M/F: 18/2; mean age: 5.20), 20 with DLD (M/F: 11/9; mean age: 5.25), and 20 TDA children (M/F:14/6; mean age:5.27) completed a picture-choice task and priming picture-description task. The results were analyzed using non-parametric methods. RESULTS: In the comprehension task, the HFA-LI and DLD groups achieved lower accuracy than the TDA group on zai-, -le, and -guo. The comprehension of aspect markers in the HFA-LI and DLD groups was affected by lexical aspect. In the production task, the HFA-LI and DLD groups produced fewer sentences with the target aspect marker for all four aspect markers than the TDA group. However, they produced more sentences with bare verb forms for zai- and -guo than the TDA group. Furthermore, all three groups tended to combine aspect markers with their semantically inherent types of verbs (e.g, zai-+Activity verbs). The HFA-LI group produced more sentences irrelevant to the task than the other two groups for -zhe and -guo, and some children in the HFA-LI group produced ungrammatical sentences in which both the progressive zai- and perfective -le were used. CONCLUSIONS: Children with HFA-LI and DLD demonstrate similarities in the comprehension and production of Mandarin aspect markers, given their poor comprehension of the aspect markers zai-, -le and -guo, and poor production of all four aspect markers compared to their TDA peers. Their performance was also impacted by lexical aspect.