A hybrid constructed wetland for organic-material and nutrient removal from sewage: Process performance and multi-kinetic models.

A pilot-scale hybrid constructed wetland with vertical flow and horizontal flow in series was constructed and used to investigate organic material and nutrient removal rate constants for wastewater treatment and establish a practical predictive model for use. For this purpose, the performance of multiple parameters was statistically evaluated during the process and predictive models were suggested. The measurement of the kinetic rate constant was based on the use of the first-order derivation and Monod kinetic derivation (Monod) paired with a plug flow reactor (PFR) and a continuously stirred tank reactor (CSTR). Both the Lindeman, Merenda, and Gold (LMG) analysis and Bayesian model averaging (BMA) method were employed for identifying the relative importance of variables and their optimal multiple regression (MR). The results showed that the first-order-PFR (M2) model did not fit the data (P > 0.05, and R2 < 0.5), whereas the first-order-CSTR (M1) model for the chemical oxygen demand (CODCr) and Monod-CSTR (M3) model for the CODCr and ammonium nitrogen (NH4-N) showed a high correlation with the experimental data (R2 > 0.5). The pollutant removal rates in the case of M1 were 0.19 m/d (CODCr) and those for M3 were 25.2 g/m2∙d for CODCr and 2.63 g/m2∙d for NH4-N. By applying a multi-variable linear regression method, the optimal empirical models were established for predicting the final effluent concentration of five days' biochemical oxygen demand (BOD5) and NH4-N. In general, the hydraulic loading rate was considered an important variable having a high value of relative importance, which appeared in all the optimal predictive models.

Antimicrobial Resistance in Chlamydiales, Rickettsia, Coxiella, and Other Intracellular Pathogens.

This article will provide current insights into antimicrobial susceptibilities and resistance of an important group of bacterial pathogens that are not phylogenetically related but share lifestyle similarities in that they are generally considered to be obligate intracellular microbes. As such, there are shared challenges regarding methods for their detection and subsequent clinical management. Similarly, from the laboratory perspective, susceptibility testing is rarely undertaken, though molecular approaches might provide new insights. One should also bear in mind that the highly specialized microbial lifestyle restricts the opportunity for lateral gene transfer and, consequently, acquisition of resistance.

How informative is the mouse for human gut microbiota research?

The microbiota of the human gut is gaining broad attention owing to its association with a wide range of diseases, ranging from metabolic disorders (e.g. obesity and type 2 diabetes) to autoimmune diseases (such as inflammatory bowel disease and type 1 diabetes), cancer and even neurodevelopmental disorders (e.g. autism). Having been increasingly used in biomedical research, mice have become the model of choice for most studies in this emerging field. Mouse models allow perturbations in gut microbiota to be studied in a controlled experimental setup, and thus help in assessing causality of the complex host-microbiota interactions and in developing mechanistic hypotheses. However, pitfalls should be considered when translating gut microbiome research results from mouse models to humans. In this Special Article, we discuss the intrinsic similarities and differences that exist between the two systems, and compare the human and murine core gut microbiota based on a meta-analysis of currently available datasets. Finally, we discuss the external factors that influence the capability of mouse models to recapitulate the gut microbiota shifts associated with human diseases, and investigate which alternative model systems exist for gut microbiota research.

Inflammation-associated enterotypes, host genotype, cage and inter-individual effects drive gut microbiota variation in common laboratory mice.

BACKGROUND: Murine models are a crucial component of gut microbiome research. Unfortunately, a multitude of genetic backgrounds and experimental setups, together with inter-individual variation, complicates cross-study comparisons and a global understanding of the mouse microbiota landscape. Here, we investigate the variability of the healthy mouse microbiota of five common lab mouse strains using 16S rDNA pyrosequencing. RESULTS: We find initial evidence for richness-driven, strain-independent murine enterotypes that show a striking resemblance to those in human, and which associate with calprotectin levels, a marker for intestinal inflammation. After enterotype stratification, we find that genetic, caging and inter-individual variation contribute on average 19%, 31.7% and 45.5%, respectively, to the variance in the murine gut microbiota composition. Genetic distance correlates positively to microbiota distance, so that genetically similar strains have more similar microbiota than genetically distant ones. Specific mouse strains are enriched for specific operational taxonomic units and taxonomic groups, while the 'cage effect' can occur across mouse strain boundaries and is mainly driven by Helicobacter infections. CONCLUSIONS: The detection of enterotypes suggests a common ecological cause, possibly low-grade inflammation that might drive differences among gut microbiota composition in mammals. Furthermore, the observed environmental and genetic effects have important consequences for experimental design in mouse microbiome research.

Synthesis of ansa-[n]silacyclopentadienyl-cycloheptatrienyl-chromium complexes (n = 1, 2): novel precursors for polymers bearing chromium in the backbone.

Reaction of [(eta5-C5H4Li)(eta7-C7H6Li)Cr]tmeda with a variety of dialkyl(dichloro)silanes in aliphatic solvents afforded the corresponding [1]silatrochrocenophanes. Structural characterization by X-ray diffraction analysis of the [1]silatrochrocenophanes bearing Me2Si, (iPr)2Si, and silacyclobutane bridges revealed tilt angles alpha of 15.56(12) degrees , 15.8(1) degrees , and 16.33(17) degrees , respectively. Analogously, a [2]silatrochrocenophane (6) was prepared in excellent yield by reaction of [(eta5-C5H4Li)(eta7-C7H6Li)Cr]tmeda with 1,2-dichloro-1,1,2,2-tetramethyldisilane. This complex also was characterized structurally and exhibited a tilt angle alpha of 2.60(15) degrees. The [1]silatrochrocenophane bearing the Me2Si bridge underwent facile and regioselective carbon-silicon bond cleavage with [Pt(PEt3)4] to give a very high yield of an oxidative addition product. The ring-opening polymerization of these novel [1]silatrochrocenophanes afforded ring-opened chromium-based polymers.

Activation of a Si=Si Bond by eta1-coordination to a transition metal.

Reaction of the disilenide 1 with Cp2ZrCl2 yields 2, the first transition metal complex with an eta1-sigma-bonded disilene moiety. The compound 2 exhibits a strongly red-shifted UV-vis absorption, resulting in an intensely green color. The Si=Si bond in 2 is considerably activated as shown by the rearrangement to a silyl-substituted zirconocene 3. X-ray diffraction studies on 2 reveal that the Si=Si bond is significantly longer than that in the precursor 1. Conversely, the Zr-Si distance is considerably smaller than the corresponding distance in 3, suggesting a certain degree of electron donation toward the 16e- zirconium center.