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This study aimed to isolate a novel archaeon capable of simultaneously producing methane and bioflocculants. The isolated methanogen was identified as Methanosarcina spelaei RK-23 by molecular characterization. Strain RK-23 grew with different carbon sources, but acetate was found to be the most beneficial carbon source for the production of methane and bioflocculants. Moreover, RK-23 produced methane and bioflocculants within an initial pH range of 5.0–8.0, with an optimal pH for methane production of 6.5 and flocculating activity of 7.0. In addition, strain RK-23 exhibited tolerance to high-salinity conditions and produced methane and bioflocculants within 0–1.2 M NaCl, with an optimum NaCl concentration of 0.3 M. The methane production and flocculating activity of strain RK-23 under optimal culture conditions were 17.4 mmol methane/mol acetate and 95.6%, respectively. MBF-23 mostly consisted of 83.5% carbohydrates and 14.3% proteins. Furthermore, the bridging of adsorption is believed to be the main bioflocculation mechanism in this study. • A novel bioflocculant-producing methanogen, Methanosarcina spelaei RK-23, was isolated. • RK-23 converted acetate to methane and MBF-23. • RK-23 secreted methane and MBF-23 within a wide salinity range. • MBF-23 was negatively charged, with a molecular weight of 3.5 × 106 Da. [ABSTRACT FROM AUTHOR]

Highlights: [•] The bioflocculant-producing bacteria isolated from a sputum sample. [•] The bioflocculant is stable at wide ranges of pH and temperature. [•] Cation-independent bioflocculant produced by Klebsiella pneumoniae. [•] It could flocculate a variety of real wastewaters. [•] 79.4% flocculating activity for amoebae cysts was achieved with the bioflocculant. [ABSTRACT FROM AUTHOR]

There is controversy about whether the amniotic fluid contains bacteria. With the use of sequencing-based methods, recent studies report that the amniotic fluid is colonized by microorganisms. However, background-contaminating DNA might lead to false-positive findings when such a low microbial biomass sample is examined. The purpose of this study was to determine whether the midtrimester amniotic fluid of patients who subsequently had normal pregnancy outcomes contains a microbial signature. In this prospective cohort study, 42 amniotic fluid samples were collected from 37 pregnancies (5 twin and 32 singletons) during genetic amniocentesis in the midtrimester. The subsequent pregnancy outcomes of all the participants were followed. Multiple methods were used to detect the presence of microorganisms in this study, which included cultivation, quantitative real-time polymerase chain reaction, and 16S ribosomal RNA gene sequencing. Multiple positive control samples (n=16) served as quality control samples and included 3 adult fecal samples, 4 vaginal swabs, and 9 artificial bacterial communities that were run in parallel with negative control samples (n=12) that included 4 samples from the hospital operating room and 8 samples from the laboratory, to account for background-contaminating DNA during each step of the experiments. No bacteria under anaerobic or aerobic conditions or genital mycoplasmas were cultured from any of the amniotic fluid samples. Quantitative polymerase chain reaction did not reveal greater copy numbers of 16S ribosomal RNA gene in amniotic fluid samples than in negative control samples. 16S Ribosomal RNA gene sequencing did not indicate a significant difference in the microbial richness or community structures between amniotic fluid and negative control samples. With multiple methods of microbiologic inquiry, no microorganisms were identified in the midtrimester amniotic fluid of healthy pregnancies with a normal pregnancy outcome. [ABSTRACT FROM AUTHOR]

A time series of Hα filtergrams and two-dimensional Hα spectral data of the well-known post-flare loop system of April 27, 1981 are obtained at the Yunnan Observatory. The two-dimensional spectral data are analyzed quantitatively by means of the `multi-cloud model'' method. The line-of-sight velocity fields of the post-flare loop system are derived for three different times. The post-flare loop system is composed of a loop and an ejection. The loop almost faces the observer and the ejection is along the line-of-sight. A `double-loop'' model is proposed in order to explain the structure and evolution of the post-flare loop system. The distributions of the line-of-sight velocity and the evolution time of the post-flare loop system derived from a free-fall model are similar to those obtained from the observations. [Copyright &y& Elsevier]

We analysed precipitation and river water samples from the Lijiang River basin with the aim of understanding the important role of acid rain components, especially NH 4 , in chemical weathering of karst areas. First, analysis of the hydrochemical characteristics revealed the following: In the precipitation samples, the volume-weighted mean pH was 4.91, and the acid rain rate was 65%. The major ion composition was characterized by a dominance of NH 4 , Ca, SO 4 and NO 3 , accounting for 40.0%, 35.3%, 46.3% and 30.5%, respectively, of the total cation and anion concentrations. In the river water samples, the pH ranged from 6.75 to 9.16, with an average of 7.55. The major hydrogeochemical species in the river water samples were Ca–HCO 3 and Mg–HCO 3. Second, by employing chloride-normalized ratios of the other major ions in precipitation, we estimated that the contributions of SO 4 and NO 3 from the atmosphere to the river were53.6% and 35.0%, respectively. Third, combining the hydrochemical index with the value of δ13C DIC and using the hydrochemical composition method showed that the proportion of carbonate weathered (R) by NH 4 , H 2 SO 4 and HNO 3 from acid rain accounted for 9.3%, 9.4% and 3.1% of the total weathering rate, respectively, and the proportions in the upper reaches were significantly higher than those in the lower reaches of the river. The average values of the carbonate weathering proportion (R) and the carbonate weathering rate (CWR) due to acid rain were approximately 22.0% and 2.1 t/km2/yr, respectively. Taken together, our results revealed that carbonate weathering by acid rain can significantly increase the carbonate weathering rate, which is essential information for accurate estimation of the carbon cycle (namely, inorganic carbon sources and sinks). Image 1 • Analysis of hydrochemical characteristics of precipitation and river water. • NH 4 (H), H 2 SO 4 and HNO 3 may provide the required protons for weathering reactions. • Carbonate weathering by acid rain can significantly increase weathering rate. [ABSTRACT FROM AUTHOR]