Analysis of effect of nicotine on microbial community structure in sediment using PCR-DGGE fingerprinting

Solid or liquid waste containing a high concentration of nicotine can pollute sediment in rivers and lakes, and may destroy the ecological balance if it is directly discharged into the environment without any treatment. In this study, the polymerase chain reaction(PCR) and denaturing gradient gel electrophoresis(DGGE) method was used to analyze the variation of the microbial community structure in the control and nicotinecontaminated sediment samples with nicotine concentration and time of exposure. The results demonstrated that the growth of some bacterial species in the nicotine-contaminated sediment samples was inhibited during the exposure. Some bacteria decreased in species diversity and in quantity with the increase of nicotine concentration or time of exposure, while other bacteria were enriched under the effect of nicotine, and their DGGE bands changed from undertones to deep colors. The microbial community structure, however, showed a wide variation in the nicotinecontaminated sediment samples, especially in the sediment samples treated with high-concentration nicotine. The Jaccard index was only 35.1%between the initial sediment sample and the sediment sample with a nicotine concentration of 0.030 mg/g after 28 d of exposure. Diversity indices showed that the contaminated groups had a similar trend over time. The diversity indices of contaminated groups all decreased in the first7 d after exposure, then increased until day 42. It has been found that nicotine decreased the diversity of the microbial community in the sediment.     

An introduction to the new degradation of polyvinyl chloride (PVC) shower hose

Recently, polyvinyl chloride (PVC) shower hoses have hardened throughout the eastern Shizuoka Prefecture, Japan. According to the elemental analysis results, the carbon and oxygen concentrations were much lower in the damaged hoses. These findings reveal that oxygen-containing, carbon-based plasticisers may leach from the damaged hose. As a result, the hoses lost flexibility after one year of use. The highest number of heterotrophic bacteria was detected by PCR-denaturing gradient gel electrophoresis in the shower water, and the bacterial DNA concentration was higher when hot water contacted the hose surface. I conclude that the plasticiser was leached from the stiffened hose through a bioaccumulation process.     

孝感酒酿微生物多样性及优势菌特性研究

采用PCR-变性梯度凝胶电泳(PCR-DGGE)技术法检测不同酒酿样品中微生物多样性,发现酒酿中包含酿酒酵母属(Saccha-romyces sp.)、毕赤酵母属(Pichia sp.)、乳杆菌属(Lactobacillus sp.)和葡萄糖杆菌属(Gluconobacter sp.)等。从3种酒酿中分离3株优势酵母菌、1株乳酸杆菌和1株球菌,经鉴定为2株酿酒酵母(Saccharomyces cerevisiae)、1株贝酵母(Saccharomyces bayanus)、坚韧肠球菌(Enterococcus durans)和植物乳杆菌(Lactobacillus plantarum)。3株优势酵母菌MJN2、17JN2和MJN3表现了较强的产酒精能力,培养48h后,酒精产量分别达到1.4%vol、1.5%vol和2.2%vol,2株优势乳酸菌JN3和JN1表现出了较强的产酸能力,培养24h后,pH值分别达到5.13和3.69。     

PCR-DGGE在制浆造纸废水处理微生物检测中的应用

聚合酶链式反应结合变性梯度凝胶电泳（PCR—DGGE）技术是近年来微生物分子生态学的研究重点，具有简便快速、可靠性强、不需要进行微生物的培养等优点，被广泛应用于废水处理系统中微生物的多样性和动态性的分析。本文概述了PCR—DGGE技术的发展、原理、影响因素以及在国内外废水处理的微生物检测中的应用现状。将该技术应用于制浆造纸废水处理的微生物检测中对理解污染物的降解机理有非常重要的意义，具有良好的发展前景。     

PCR-DGGE指纹分析技术在食品微生物检测中的应用

多聚酶链式反应结合变性梯度凝胶电泳指纹分析技术(PCR-DGGE)常用于分析自然环境中微生物群体的遗传多样性,具有可重复和容易操作且不需要进行微生物培养等特点,近年来该技术开始作为食品微生物的研究手段。本文概述了PCR-DGGE指纹分析技术在国外发酵食品及相关生态环境的研究中的应用现状与前景。     

膜法生产饮用水过程中纳滤膜生物污染的研究

研究了在地表水生产饮用水过程中纳滤膜上微生物的污染情况,以分子生物学方法研究其纳滤膜在不同过滤时间的主要污染生物种类。通过对膜的水通量、进出水的水质变化等条件进行膜污染的研究,其结果表明纳滤膜对水中生物去除效率很高;通过对提取不同时期污膜上微生物DNA进行PCR-DGGE指纹图谱聚类分析发现,在污染的纳滤膜上,变形菌纲、杆菌属的细菌则成为了优势细菌。研究为减轻膜生物污染的研究提供了理论基础。     

Effect of organic loading on a novel hydrogen bioreactor

This study investigated the impact of six organic loading rates (OLR) ranging from 6.5 gCOD/L-d to 206 gCOD/L-d on the performance of a novel integrated biohydrogen reactor clarifier systems (IBRCSs) comprised a continuously stirred reactor (CSTR) for biological hydrogen production, followed by an uncovered gravity settler for decoupling of solids retention time (SRT) from hydraulic retention time (HRT). The system was able to maintain a high molar hydrogen yield of 2.8 mol H₂/mol glucose at OLR ranging from 6.5 to 103 gCOD/L-d, but dropped precipitously to approximately 1.2 and 1.1 mol H₂/mol glucose for the OLRs of 154 and 206 gCOD/L-d, respectively. The optimum OLR at HRT of 8 h for maximizing both hydrogen molar yield and volumetric hydrogen production was 103 gCOD/L-d. A positive statistical correlation was observed between the molar hydrogen production and the molar acetate-to-butyrate ratio. Biomass yield correlated negatively with hydrogen yield, although not linearly. Analyzing the food-to-microorganisms (F/M) data in this study and others revealed that, both molar hydrogen yields and biomass specific hydrogen rates peaked at 2.8 mol H₂/mol glucose and 2.3 L/gVSS-d at F/M ratios ranging from 4.4 to 6.4 gCOD/gVSS-d. Microbial community analysis for OLRs of 6.5 and 25.7 gCOD/L-d showed the predominance of hydrogen producers such as Clostridium acetobutyricum, Klebsiella pneumonia, Clostridium butyricum, Clostridium pasteurianum. While at extremely high OLRs of 154 and 206 gCOD/L-d, a microbial shift was clearly evident due to the coexistence of the non-hydrogen producers such as Lactococcus sp. and Pseudomonas sp.     

Characterization by culture-dependent and culture-independent methods of the bacterial population of suckling-lamb packaged in different atmospheres

This study offers insight into the dynamics of bacterial populations in fresh cuts of suckling lamb under four different atmospheric conditions: air (A), and three Modified Atmosphere Packaging (MAP) environments, 15%O₂/30%CO₂/55%N₂ (C, commercial), 70%O₂/30%CO₂ (O), and 15%O₂/85%CO₂ (H) for 18 days. Microbial analyses by both conventional methods and PCR-DGGE were performed. Controversial and surprising results emerged from comparing both methods in relation to the genus Pseudomonas. Thus, conventional methods detected the presence of high numbers of Pseudomonas colonies, although PCR-DGGE only detected this genus in air-packaged samples. PCR-DGGE detected higher microbial diversity in the control samples (A) than in the modified atmospheres (C, O, H), having atmosphere H the fewest number of species. Brochothrix thermosphacta, LAB (Carnobacterium divergens and Lactobacillus sakei), and Escherichia spp. were detected in all the atmospheres throughout storage. Moreover, previously undescribed bacteria from lamb meat such as Enterobacter hormaechei, Staphylococcus equorum and Jeotgalicoccus spp. were also isolated in this study by DGGE. Additionally, qPCR analysis was used to detect and characterize strains of Escherichia coli. Virulence genes (stx₁, stx₂ and eae) were detected throughout storage in 97% of the samples. A high CO₂ atmosphere was the most effective packaging combination doubling storage time in comparison with commercial atmosphere.