Profiling bacterial survival through a water treatment process and subsequent distribution system

AIMS: To profile fractions of active bacteria and of bacteria culturable with routine heterotrophic plate count (HPC) methods through a typical water treatment process and subsequent distribution system. In doing so, investigate how water treatment affects both bacterial abundance and diversity, and reveal the identities of active bacteria not detected by traditional HPC culture. METHODS AND RESULTS: Profiling active fractions was performed by flow cytometric cell sorting of either membrane-intact (BacLight kit) or enzymatically active (carboxyfluorescein diacetate, CFDA) bacteria, followed by eubacterial 16S rDNA-directed PCR and denaturing gradient gel electrophoresis (DGGE). Water treatment significantly reduced active bacterial numbers detected by the BacLight kit and CFDA assay by 2.89 and 2.81 log respectively. Bacterial diversity was also reduced from > 20 DGGE bands in the active fractions of reservoir water to only two bands in the active fractions of finished water. These two bands represented Stenotrophomonas maltophila, initially culturable by HPC, and a Burkholderia-related species. Both species maintained measurable traits of physiological activity in distribution system bulk water but were undetected by HPC. CONCLUSIONS: Flow cytometric cell sorting with PCR-DGGE, to assess water treatment efficacy, identified active bacteria from a variety of major phylogenetic groups undetected by routine HPC. Following treatment S. maltophila and a Burkholderia-related species retained activity and entered distribution undetected by HPC. SIGNIFICANCE AND IMPACT OF THE STUDY: Methods used here demonstrate how water treatment operators can better monitor water treatment plant efficacy and assess distribution system instability by the detection and identification of active bacteria recalcitrant to routine HPC culture.     

An arabinogalactan isolated from the stems of Cistanche deserticola induces the proliferation of cultured lymphocytes

A purified polysaccharide ACDP-2 was isolated from water extract of the stems of Cistanche deserticola. Chemical and spectroscopic analyses indicated that ACDP-2 is a highly branched arabinogalactan polymer that composes of linked d-galactopyranose and d-glucopyranose, which contains predominantly a branching point at the 6-carbon. The branched side-chains compose of terminal-, 1,5-, and 1,3,5-linked arabinofuranosyl residues. ACDP-2 showed an effect in stimulating the immune response, which when applied onto the cultured mouse lymphocytes induced the cell proliferation in a dose-dependent manner.     

Characterization of zinc oxide nanocrystals with different morphology for application in ultraviolet‐light photocatalytic performances on rhodamine B

ZnO nanostructures of different morphology (nanorods, nano‐leaf, nanotubes) were favourably grown using a chemical precipitation process. The prepared ZnO nanostructures were characterized systematically using absorption spectroscopy, emission spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared studies. XRD results showed the hexagonal wurtzite phase of the synthesized ZnO nanostructures. Structural properties such as average crystallite size, lattice constants, volume of the unit cell, atomic fraction, and structural bonds were also studied. The optical band gap of the synthesized ZnO nanocrystals varied from 3.52 eV to 3.69 eV with high quantum yield of the blue emission (~420 nm). Urbach energy for ZnO nanocrystals was calculated to be 0.702 eV, 0.901 eV, and 0.993 eV for nanorods, nano‐leaf, and tube like ZnO crystals, respectively. Morphology of the fabricated nanostructures was investigated using SEM. Photocatalytic degradation of rhodamine B (Rh B) in solution under UV irradiation was explored with different ZnO morphology. Photocatalytic experiments showed that ZnO nano‐leaf had a higher degradation rate of photocatalytic activity of photodegrading Rh B compared with the other tube shape and rods shape nanostructures. The Rh B dye degraded considerably by ～79.05%, 74.41%, and 69.8% within 120 min in the presence of the as‐fabricated fern nano‐leaf, nanotubes, and nanorods of the ZnO nanocrystals at room temperature.     

Exposure to T-cycles of 22 and 23 h during lactation modifies the later dissociation of motor activity and temperature circadian rhythms in rats

Early environmental conditions may affect the development and manifestation of circadian rhythms. This study sought to determine whether the maintenance of rats under different T-cycles during lactation influences the subsequent degree of dissociation of the circadian rhythms of motor activity and core body temperature. Two groups of 22 day-old Wistar rats were kept after weaning under T-cycles of 22 h (T22) or 23 h (T23) for 70 days. Subsequently, they were kept in constant darkness (DD). Half of the animals in each group were born and reared under these experimental conditions, while the other half were reared until weaning under 24 h LD cycles (T24). Rats transferred from T24 to T22 or T23 showed two circadian components in motor activity and temperature, one entrained by light and the other free-running. In T22, there was also desynchronization between temperature and motor activity. Rats submitted to T23 from birth showed higher stability of the 23 h component than rats transferred from T24 to T23 after weaning. However, in comparison to rats born under T24 and subsequently changed to T22, animals submitted to T22 from birth showed shorter values of the period of the non-light-dependent component during T22, more aftereffects when transferred to DD, and a lack of desynchronization between motor activity and temperature. The results suggest that T-cycles in the early environment may modify overt rhythms by altering the internal coupling of the circadian pacemaker.     

Effects of mercury on microbial biomass and enzyme activities in soil

Mercury (Hg) is a persistent soil pollutant that affects soil microbial activity. We monitored the changes in soil microbial biomass and activity of enzymes, including alkaline phosphatase, arylsulfatase, fluorescein diacetate (FDA) hydrolytic activity, and o-diphenol oxidase (o-DPO) in three soils contaminated with different concentrations of Hg. Increasing levels of Hg, from 0.5 to 10 μmol/g of dried soil, generally depressed microbial activity; however, the effects of Hg on soil microbial activity depended on soil type and composition, particularly organic matter content. o-DPO was less affected by Hg than the other three enzymes tested. Our results indicate that the analysis of microbial biomass content and soil-enzyme activities may be used to predict the soil quality contaminated with Hg.     

Effect of polyols on the conformational stability and biological activity of a model protein lysozyme

The purpose of this study was to investigate the stabilizing action of polyols against various protein degradation mechanisms (eg, aggregation, deamidation, oxidation), using a model protein lysozyme. Differential scanning calorimeter (DSC) was used to measure the thermodynamic parameters, mid point transition temperature and calorimetric enthalpy, in order to evaluate conformational stability. Enzyme activity assay was used to corroborate the DSC results. Mannitol, sucrose, lactose, glycerol, and propylene glycol were used as polyols to stabilize lysozyme against aggregation, deamidation, and oxidation. Mannitol was found to stabilize lysozyme against aggregation, sucrose against deamidation both at neutral pH and at acidic pH, and lactose against oxidation. Stabilizers that provided greater conformational stability of lysozyme against various degradation mechanisms also protected specific enzyme activity to a greater extent. It was concluded that DSC and bioassay could be valuable tools for screening stabilizers in protein formulations.     

Significance of metal ion supplementation in the fermentation medium on the structure and anti-tumor activity of Tuber polysaccharides produced by submerged culture of Tuber melanosporum

The significance of metal ion supplementation in the fermentation medium on the structure and anti-tumor activity of Tuber polysaccharides was systematically studied in the submerged fermentation of Tuber melanosporum. The lowest weight-average molecular weight (M_w) (i.e., 115.3 × 10⁴ g/mol) of intracellular polysaccharides (IPS) was obtained when Mg²⁺ and K⁺ was added in the fermentation medium. The IPS with the lower M_w exhibited a higher inhibition ratio against S-180 tumor cells. The compact conformation of extracellular polysaccharides (EPS) was formed when only K⁺ was supplied in the fermentation medium. Interestingly, EPS with compact conformation exhibited a higher inhibition ratio (i.e., 59.2%) than EPS with branched polymer chain (i.e., 9.2%) against A549 tumor cells. The highest inhibition ratio for EPS with α-glycosidic linkages against the tumor cell line HepG2 reached 32.2% when Mg²⁺ or K⁺ was supplied in the fermentation medium. The addition of metal ion Mg²⁺, K⁺, and their combination to the fermentation medium is a vital factor affecting the structures of Tuber polysaccharides, which further determine their anti-tumor activities. The information obtained in this work will be useful for the efficient and directed production of polysaccharides with anti-tumor activities by the submerged fermentation of edible fungi mycelium.     

海洋短小枯草芽胞杆菌的鉴定及抑菌活性分析

对从连云港东西连岛海泥样品中分离得到的菌株Bacillus pumilus HX2-2的分类地位、生长条件和抑菌活性进行了研究。经过形态特征、生理生化性质及16S r DNA序列分析鉴定,该菌属于短小芽胞杆菌。不同温度、盐度、pH培养条件下测定菌液吸光度OD600值,表明该菌是一株轻度嗜盐菌,最适温度、盐度、pH分别为30℃、3%、7.0~8.0。在不同病原真菌的平板抑菌活性试验中,该菌对草莓尖胞镰刀菌、马铃薯炭疽病菌和水稻立枯丝核菌表现出显著的抑菌作用。菌株B.pumilus HX2-2是一株短小芽胞杆菌,具有广谱抑菌活性,具有进一步研究的价值。     

星星草(Puccinellia tenuiflora)人工草地氮素积累对松嫩盐碱草地植被演替的影响

通过对星星草(Puccinellia tenuiflora)生长不同年数盐碱土壤氮素营养状况的比较,研究氮素积累作用的机理,并探讨其在植被演替中的可能作用.结果表明:在一维生态位空间(土壤氮含量)星星草和羊草(Leymus chinense)之间具有较小的生态位分离值和较大的生态位重叠值,表明羊草对土壤高含氮量具有较强的竞争能力.这些也许是羊草以及其他植物在星星草生长一定年数后能够侵入碱斑土壤的机制.星星草作为盐碱土壤改良和植被恢复的先锋植物,它的生长增强了盐碱草地土壤氮素的矿质化作用和生物固氮强度,并减弱了氮素随地表径流的损失.最终促进了盐碱草地的氮素沉积,达到了适合于其它物种(如羊草)生长的水平,从而使碱斑植被得以恢复.