The Innate Immune Glycoprotein Lactoferrin Represses the Helicobacter pylori cag Type IV Secretion System

Chronic infection with Helicobacter pylori increases risk of gastric diseases including gastric cancer. Despite development of a robust immune response, H. pylori persists in the gastric niche. Progression of gastric inflammation to serious disease outcomes is associated with infection with H. pylori strains which encode the cag Type IV Secretion System (cag T4SS). The cag T4SS is responsible for translocating the oncogenic protein CagA into host cells and inducing pro-inflammatory and carcinogenic signaling cascades. Our previous work demonstrated that nutrient iron modulates the activity of the T4SS and biogenesis of T4SS pili. In response to H. pylori infection, the host produces a variety of antimicrobial molecules, including the iron-binding glycoprotein, lactoferrin. Our work shows that apo-lactoferrin exerts antimicrobial activity against H. pylori under iron-limited conditions, while holo-lactoferrin enhances bacterial growth. Culturing H. pylori in the presence of holo-lactoferrin prior to co-culture with gastric epithelial cells, results in repression of the cag T4SS activity. Concomitantly, a decrease in biogenesis of cag T4SS pili at the host-pathogen interface was observed under these culture conditions by high-resolution electron microscopy analyses. Taken together, these results indicate that acquisition of alternate sources of nutrient iron plays a role in regulating the pro-inflammatory activity of a bacterial secretion system and present novel therapeutic targets for the treatment of H. pylori-related disease.     

Fabrication of bacterial cellulose with high efficient loading of Ag and TiO2 nanoparticles for removing organic dyes

As a new advanced oxidation technology, photocatalytic technology has broad application prospects in the field of wastewater treatment. However, in the actual use process, there will be difficulties in catalyst recovery and reuse. This article successfully prepared bacterial cellulose (BC) loaded silver and titanium dioxide nanoparticles (Ag-plated TiO₂/BC composite pellicle) by in situ embedding method. BC not only works as the carrier to load TiO₂ and Ag NPs but also adsorbs dyes to promote the reaction. As a reusable photocatalytic film, it is convenient to use and recycle in terms of testing and characterization compared with powders. The results show that Ag and TiO₂ nanoparticles were closely embedded in BC. We evaluated the photocatalytic degradation performance of the catalyst on methylene blue (MB), active red X-3B, and Rhodamine B. When the reaction time was 2 h, the dye removal rates were 71%, 68%, and 82.6%. At the same time, through the inhibition zone experiment, it was found that the material has a certain inhibitory effect on both Escherichia coli and Staphylococcus aureus. Therefore, the supported catalyst prepared by this method has the advantages of high catalytic activity, relatively stable property, easy recovery, and tailorability, making it potentially applicable in sewage post-treatment links.     

Analysis of the corrosion failure causes of shale gas surface pipelines

A shale gas gathering and transportation pipeline in a good block in Sichuan Province started leaking after less than a year of operation. To investigate the causes of corrosion of the sulfate-reducing bacteria (SRB), optical microscopy, scanning electron microscopy, and X-ray diffraction were used to analyze the corrosion and perforation of the shale gas surface pipeline in conjunction with bacterial corrosion simulation experiments. The results showed that the pipeline material (L360N) conformed to the requirements of the American Petroleum Institute 5 L standard and that extracellular polymeric substances were present in the corrosion pits. The corrosion products mainly included FeCO₃, FeS, CaCO₃, MgCO₃, and Fe mineralization. At 40°C, the uniform corrosion rate of L360N in the simulation experiment was 0.234 mm/a, and the local corrosion rate was 0.458 mm/a. SRB, saprophytes, and iron bacteria were detected in the on-site water medium and corrosion products, indicating that the main causes of shale gas pipeline corrosion are bacterial and CO₂ corrosion.     

细菌纤维素合成与鉴定研究综述

细菌纤维素（BC）因其独特性能被广泛应用于医药、食品等领域，目前其高产量菌株筛选、合成成本降低及合成途径改良等成为研究热点。本文依据国内外文献并结合团队研究成果对BC合成与鉴定的相关研究进行综述。首先对BC合成菌筛选及碳源利用的研究进行了分析，总结了降低BC合成成本的研究思路。其次对鉴定菌株合成产物的方法进行了归纳，总结了不同方法的特点。然后结合本团队筛选出的BC生产菌XJL-06-4 BC合成酶基因分析结果，综述了BC合成途径、合成酶存在形式以及基因水平调控作用，为BC在分子水平上通过改变合成途径提高产量提供新思路。最后，总结BC微生物发酵生产存在的问题，多角度提出解决方案。     

不同含量低污染水对人工湿地中细菌的影响研究

探究水平流人工湿地(HFCW)系统处理低污染水过程中,相同COD/ρ(TN)下不同碳氮含量对细菌群落结构的影响。结果表明,进水为较高碳氮含量的HFCW(HF1)和进水为较低碳氮含量的HFCW(HF2)对COD和TN的去除效率具有一定的差异,HF1和HF2对COD的去除效率分别为48.26%和28.89%,对TN的去除率分别为79.06%和81.87%。HF1中细菌的丰富度和多样性均高于HF2,HF1中富集的优势细菌为Chloroflexaceae、Comamonadaceae和Rhodocyclaceae,均具有异养反硝化功能,HF2中富集的优势细菌为Xanthomonadaceae和Rhodocyclaceae,其中Xanthomonadaceae具有自养反硝化功能。COD、NH4^+-N和NO3^--N对HF1中细菌群落的影响大于对HF2中细菌群落的影响,HF1中COD对细菌群落的影响大于NH4^+-N和NO3^--N。     

Novel superabsorbent materials from bacterial cellulose

A novel process for the production of superabsorbent materials (hydrogels) from bacterial cellulose (BC) was developed. Prior to crosslinking with a water‐soluble polyethylene glycol diacrylate (PEGDA), BC was first carboxymethylated and functionalized with glycidyl methacrylate. The degree of crosslinking influenced the swelling properties of the hydrogels. The use of greater amounts of PEGDA enhanced the formation of a thicker macromolecular network containing fewer capillary spaces in the crosslinked gel. The maximum water retention value of the hydrogels containing 2.5–3.5 mmol of carboxyl groups per gram of gel reached 125 g g^?1 in distilled water, and 29 g g^?1 in saline (0.9% NaCl solution). The highly porous hydrogel architecture with a pore size of 350–600 µm created a high specific surface area. This enables rapid mass penetration in superabsorbent applications. The superabsorbent hydrogels reached 80% of their maximum water absorption capacity in 30 min. © 2018 Society of Chemical Industry     

Enzymatic Responses to Low-Intensity Radiation of Tritium

The present study considers a possible role of enzymatic reactions in the adaptive response of cells to the beta-emitting radionuclide tritium under conditions of low-dose exposures. Effects of tritiated water (HTO) on the reactions of bacterial luciferase and NAD(P)H:FMN-oxidoreductase, as well as a coupled system of these two reactions, were studied at radioactivity concentrations ≤ 200 MBq/L. Additionally, one of the simplest enzymatic reactions, photobiochemical proton transfer in Coelenteramide-containing Fluorescent Protein (CLM-FP), was also investigated. We found that HTO increased the activity of NAD(P)H:FMN-oxidoreductase at the initial stage of its reaction (by up to 230%); however, a rise of luciferase activity was moderate (<20%). The CLM-FP samples did not show any increase in the rate of the photobiochemical proton transfer under the exposure to HTO. The responses of the enzyme systems were compared to the ‘hormetic’ response of luminous marine bacterial cells studied earlier. We conclude that (1) the oxidoreductase reaction contributes significantly to the activation of the coupled enzyme system and bacterial cells by tritium, and (2) an increase in the organization level of biological systems promotes the hormesis phenomenon.     

Molecular dynamics simulations of the interaction between OH radicals in plasma with poly-β-1–6-N-acetylglucosamine

Cold atmospheric plasma shows a satisfactory ability to inactivate bacterial biofilms that are difficult to remove using conventional methods in some cases. However, the researches on the inactivation mechanism are not quite sufficient. Poly-β-1–6-N-acetylglucosamine (PNAG), which is one of the important components in some biofilms, was used as the research subject, and the related mechanism of action triggered by different concentrations of the OH in plasma was studied using reactive molecular dynamics simulations. The results showed that OH radicals could not only trigger the hydrogen abstraction reaction leading to cleavage of the PNAG molecular structure, but undergo an OH addition reaction with PNAG molecules. New reaction pathways appeared in the simulations as the OH concentration increased, but the reaction efficiency first increased and then decreased. The simulation study in this paper could, to some extent, help elucidate the microscopic mechanism of the interaction between OH radicals in plasma and bacterial biofilms at the atomic level.