Evaluation of a new high-throughput method for identifying quorum quenching bacteria

Quorum sensing (QS) is a population-dependent mechanism for bacteria to synchronize social behaviors such as secretion of virulence factors. The enzymatic interruption of QS, termed quorum quenching (QQ), has been suggested as a promising alternative anti-virulence approach. In order to efficiently identify QQ bacteria, we developed a simple, sensitive and high-throughput method based on the biosensor Agrobacterium tumefaciens A136. This method effectively eliminates false positives caused by inhibition of growth of biosensor A136 and alkaline hydrolysis of N-acylhomoserine lactones (AHLs), through normalization of beta-galactosidase activities and addition of PIPES buffer, respectively. Our novel approach was successfully applied in identifying QQ bacteria among 366 strains and 25 QQ strains belonging to 14 species were obtained. Further experiments revealed that the QQ strains differed widely in terms of the type ofQQenzyme, substrate specificity and heat resistance. The QQ bacteria identified could possibly be used to control disease in aquaculture

Influence of stirring speed on SiC particles distribution in A356 liquid

A straight-blade mechanical stirrer was designed to stir A356-3.5vol%SiCp liquid in a cylindrical crucible with the capability of systematically investigating the influence of rotating speed of stirrer on the distribution of SiC particles in A356 liquid. The experimental results show that the vertical distribution of SiC particles in A356 liquid can be uniform when the rotating speed of stirrer is 200 rpm, but the radial distribution of SiC particles in A356 liquid is always nonhomogeneous regardless of the rotating speed of stirrer. The radial centrifugalization ratio of SiC particles in A356 liquid between the center and the periphery of crucible increases with the rotating speed of stirrer. The results were explained in the light of SiC particles motion subject to a combination of stirring and centrifugal effect

Characteristics and Mechanisms of Heavy Metal and MTBE Adsorption on Zeolites and Applications in Permeable Reactive Barriers

Groundwater contamination is a grave matter of concern due to its risks to the environment and human health caused by various inorganic and organic pollutants. A wide range of treatment technologies have been developed for groundwater remediation. Permeable reactive barriers (PRBs) filled with reactive media are one of the most promising in-situ technologies for groundwater remediation due to their low costs and suitability for the immobilization of multiple contaminants via adsorption, precipitation, degradation, etc. The reactive media are key components of PRBs and their selection needs to consider the immobilization ability as well as permeability. Zeolites have high adsorption capacity, diverse pore structure and high chemical stability, and therefore have been used as reactive materials. In addition, the application of zeolites as reactive media can reduce the fouling and clogging of PRBs compared to reductants like zero-valence iron (ZVI) because there is almost no production of secondary precipitates and/or gases. It is therefore important to investigate the potential of zeolites in PRBs for groundwater remediation of multiple contaminants, among which a few research gaps are particularly crucial. This thesis identifies these research gaps through a critical literature review and investigates them. Zeolites are a class of crystalline aluminosilicate minerals and have three-dimensional structures constructed by [SiO4]4- and [AlO4]5- coordination polyhedra. The isomorphic substitution of Si4+ by Al3+ produces negative charges which need to be balanced by exchangeable cations in the lattice of zeolites, leading to a high CEC. Generally, as the Si/Al ratio of zeolites increases, the thermal stability, acid strength and hydrophobicity increase, whereas the ion-exchange capacity decreases. ZSM-5, a typical hydrophobic zeolite, is effective for MTBE adsorption due to its high adsorption capacity (53.55 mg/g in batch adsorption tests) and good regeneration characteristics. The adsorption reaches equilibrium within 24 hours and follows the Langmuir isotherm model and the Hill 5 kinetic model, suggesting a monolayer and homogeneous chemisorption process. The adsorption is rarely affected by the solution pH which makes it conducive to changeable environmental conditions, but the presence of nickel ions suppresses the adsorption with Ni concentrations of 2.5–25 mg/L. The mass transfer mechanism was further explored to access the transport process of MTBE from the bulk solution to ZSM-5 pores. It was found that pore diffusion is the main rate-limiting step for the entire adsorption process. The synchrotron-based XAFS investigation was combined with batch adsorption tests and micro-structural methods to explore the mechanisms of Pb adsorption onto clinoptilolite and ZSM-5 with or without the presence of MTBE. The batch tests show that ZSM-5 has a low adsorption capacity towards Pb, while clinoptilolite is efficient (14.39 mg/g versus 94.38 mg/g at pH 4) due to their hydrophobicity and CEC. In addition, the co-existence of MTBE can rarely affect adsorption due to different adsorption mechanisms. The synchrotron-based XAFS further suggests that Pb to Si surface site occupancy and the PbO∙(H2O) type of surface coating are two common adsorption mechanisms in Pb-ZSM-5, Pb-clinoptilolite and Pb-clinoptilolite-MTBE systems. The surface “embedded” Pb uptake through the Mg site on the surface described comprised the secondary mechanism in the Pb-clinoptilolite-MTBE system. The limited available number of cleaved SiO4 rings on the surface possibly leads to the low adsorption capacity of ZSM-5. Based on the clear mass transfer mechanisms and adsorption characteristics, fixed-bed column tests were carried out to simulate the PRBs and examine the column performance of zeolites. The Dose-Response model can describe the breakthrough curves of MTBE adsorption onto ZSM-5 and onto a mixed reactive medium containing clinoptilolite granules and ZSM-5 was used in fixed-bed column tests. In comparison, MTBE adsorption onto a mixed reactive medium containing clinoptilolite powders and ZSM-5 can be described by the Logit, Thomas, and Yoon-Nelson models. In addition, MTBE adsorption onto ZSM-5 at new flow rates and bed lengths can be predicted using kinetic parameters from the BDST model without further experimental run in order to facilitate the full-scale design of columns. The maximum column adsorption capacity was found to increase with the increasing bed lengths and the decreasing flow rates and MTBE concentrations. The higher minimum thickness and corresponding longevity were obtained by the replacement of granular clinoptilolite by its powder form due to the reduction of hydraulic performance of the column and the breakthrough time, and the increase in the saturation time.China Scholarship Counci

Comparative Profiling of MicroRNAs in the Winged and Wingless English Grain Aphid, \u3cem\u3eSitobion avenae\u3c/em\u3e (F.) (Homoptera: Aphididae)

MicroRNAs (miRNAs) are short single-stranded non-coding RNAs that regulate gene expression, particularly during development. In this study, 345 miRNAs were identified from the English green aphid, Sitobion avenae (F.), of which 168 were conserved and 177 were S. avenae-specific. Quantitative comparison of miRNA expression levels indicated that 16 and 12 miRNAs were significantly up-regulated in winged and wingless S. avenae small RNA libraries, respectively. Differential expression of these miRNAs was confirmed by real-time quantitative RT-PCR validation. The putative transcript targets for these candidate miRNAs were predicted based on sequences from a model species Drosophila melanogaster and four aphid species Acyrthosiphon pisum, Myzus persicae, Toxoptera citricida, and Aphis gosspii. Gene Ontology and KEGG pathway analyses shed light on the potential functions of these miRNAs in the regulation of genes involved in the metabolism, development and wing polyphenism of S. avenae

Gut microbiome in multiple myeloma: Mechanisms of progression and clinical applications

The gut commensal microbes modulate human immunity and metabolism through the production of a large number of metabolites, which act as signaling molecules and substrates of metabolic reactions in a diverse range of biological processes. There is a growing appreciation for the importance of immunometabolic mechanisms of the host-gut microbiota interactions in various malignant tumors. Emerging studies have suggested intestinal microbiota contributes to the progression of multiple myeloma. In this review, we summarized the current understanding of the gut microbiome in MM progression and treatment, and the influence of alterations in gut microbiota on treatment response and treatment-related toxicity and complications in MM patients undergoing hematopoietic stem cell transplantation (HSCT). Furthermore, we discussed the impact of gut microbiota-immune system interactions in tumor immunotherapy, focusing on tumor vaccine immunotherapy, which may be an effective approach to improve anti-myeloma efficacy

Air-Stable NaxTMO2 Cathodes for Sodium Storage

Sodium-ion batteries are considered to be the most promising alternative to lithium-ion batteries for large-scale stationary energy storage applications due to the abundant sodium resource in the Earth' crust and as a result, relatively low cost. Sodium layered transition metal oxides (NaxTMO2) are proper Na-ion cathode materials because of low cost and high theoretical capacity. Currently most researchers focus on the improvement of electrochemical performance such as high rate capability and long cycling stability. However, for NaxTMO2, the structure stability against humid atmosphere is essentially important since most of them are instable in air, which is not favorable for practical application. Here we provide a comprehensive review of recent progresses on air-stable NaxTMO2 oxides. Several effective strategies are discussed, and further investigations on the air-stable cathodes are prospected

Genome analysis of Flaviramulus ichthyoenteri Th78T in the family Flavobacteriaceae: insights into its quorum quenching property and potential roles in fish intestine

Background: Intestinal microbes play significant roles in fish and can be possibly used as probiotics in aquaculture. In our previous study, Flaviramulus ichthyoenteri Th78(T), a novel species in the family Flavobacteriaceae, was isolated from fish intestine and showed strong quorum quenching (QQ) ability. To identify the QQ enzymes in Th78(T) and explore the potential roles of Th78(T) in fish intestine, we sequenced the genome of Th78(T) and performed extensive genomic analysis. Results: An N-acyl homoserine lactonase FiaL belonging to the metallo-beta-lactamase superfamily was identified and the QQ activity of heterologously expressed FiaL was confirmed in vitro. FiaL has relatively little similarity to the known lactonases (25.2 similar to 27.9% identity in amino acid sequence). Various digestive enzymes including alginate lyases and lipases can be produced by Th78(T), and enzymes essential for production of B vitamins such as biotin, riboflavin and folate are predicted. Genes encoding sialic acid lyases, sialidases, sulfatases and fucosidases, which contribute to utilization of mucus, are present in the genome. In addition, genes related to response to different stresses and gliding motility were also identified. Comparative genome analysis shows that Th78(T) has more specific genes involved in carbohydrate transport and metabolism compared to other two isolates in Flavobacteriaceae, both isolated from sediments. Conclusions: The genome of Th78(T) exhibits evident advantages for this bacterium to survive in the fish intestine, including production of QQ enzyme, utilization of various nutrients available in the intestine as well as the ability to produce digestive enzymes and vitamins, which also provides an application prospect of Th78(T) to be used as a probiotic in aquaculture