No abstract

Porous hybrid polymers have a vast range of prospects in the field of environmental restoration because of their excellent comprehensive performances in recent years. Two types of porous silsesquioxane/triazine hybrid polymers (PCS-TPH-1, PCS-TPH and PCS-TSA-1, PCS-TSA) were prepared by the Friedel–Crafts reaction with different ratios of phenyl- or thiophene-substituted triazine monomers and octavinylsilsesquioxane (OVS). PCS-TPH and PCS-TSA with higher specific surface areas were selected to probe their adsorption capacities for dyes and iodine vapor. Relative to PCA-TSA, PCS-TPH with a large specific surface area and a high mesoporous ratio preferred to adsorb large-sized Congo Red (CR) and rhodamine (RB) with absorption capacities of 935 and 1180 mg g–1, respectively. Under the combined action of heteroatoms and specific surface areas, PCS-TPH and PCA-TSA showed a similar I2 adsorption amount of ∼2.4 g g–1. In addition, due to the effect of charge transfer, the resulting materials can specifically respond to I2 among many other different types of anions.

Background: New Delhi metallo-beta-lactamase 1 (NDM-1) is considered to be an important factor of antimicrobial resistance in Enterobacteriaceae. In China, the blaNDM-1 gene has been mostly detected in carbapenem-resistant Acinetobacter spp. but is less reported in Enterobacteriaceae and more rarely found in E. cloacae. Objectives: This study explored the genetic features of the blaNDM-1 gene of E. cloacae and a blaNDM-1knockout mutant was constructed using Red homologous recombination. In addition, the effect of the knockout on antimicrobial resistance, growth ability, and in vitro competitiveness was investigated. Methods: The upstream and downstream structures of the blaNDM-1 gene were analyzed in ten E. cloacae isolates using primer walking and PCR mapping. A blaNDM-1 knockout mutant was constructed through Red homologous recombination and verified by PCR, RT-qPCR, and sequencing. The antimicrobial susceptibility, growth curves, and in vitro growth competitiveness were compared between the blaNDM-1 knockout mutant and the parental strain. Results: All E. cloacae study isolates except for strain T10, contained an identical blaNDM-1 gene structure. The ∆ISAba125 truncated by ISEc33 element and the bleo followed by a ∆trpF and ISSen4 was located immediately upstream and downstream of T1-T9 strains. However, the ∆ISAba125 and the bleo followed by a ∆trpF were located immediately upstream and downstream, respectively, in the T10 strain. PCR, RT-qPCR, and DNA sequencing analyses showed that the blaNDM-1 knockout mutant was successfully constructed. The blaNDM-1 knockout mutant and the parental strain exhibited similar resistance patterns to penicillin, cephalosporins, aminoglycosides, tetracycline, and quinolones. Both strains displayed similar growth curves in Luria Broth. The competition index (CI), defined as the knockout mutant/parental strain ratio was 0.69 in the competition experiment in vitro. Conclusions: The DNA regions upstream and downstream of the blaNDM-1 gene often contained insertion sequences and elements. Red homologous recombination was successfully used to knock out blaNDM-1 in E. cloacae, which allowed us to decipher the links between this gene, antimicrobial resistance, and bacterial growth competitiveness.

The precise control of scaffold elements and topologies of nanoporous materials shows great prospects in the application of adsorption and separation. In this work, two kinds of porous polymers, silsesquioxane-based porous polymers (PCSs) and triazine-based covalent–organic polymers (covalent triazine-based frameworks, CTFs), were prepared by the Heck reaction and Suzuki reaction of triazine monomers with octavinylsilsesquioxane and p-phenylboronic acid, respectively. A series of experimental results showed that the specific surface areas (S BET) and the morphological structures of the target materials can be controlled by regulating the building modules. The PCSs are irregular nanoporous aggregates with S BET values of 360∼560 m2 g–1, while the CTFs are regular hollow tubular polymers with S BET values of about 30∼70 m2 g–1. Different S BET values result in different adsorption capabilities of iodine in the volatile or solution phase. For volatile iodine, the adsorption capacity of CTFs is up to 2.5 g g–1, larger than that of PCSs, while in iodine–cyclohexane solution, the adsorption capacity of PCSs is larger than that of CTFs. Due to the fluorescence quenching caused by charge transfer between the polymers and I2, two polymers can be used to detect I2 with good selectivity and sensitivity. In this work, the porosity, fluorescence properties, and adsorption capacity of the target materials were successfully regulated by adjusting the scaffold units and topological structures of starting materials, thus realizing the sensitive detection and efficient adsorption of iodine.