The fate of environmental coliforms in a model water distribution system

A series of experiments to determine the survival characteristics of environmental and faecal coliforms in a 1.3 km long experimental pipe distribution system is described. In the first experiments, tertiary treated effluent (10(3)-10(4) coliforms ml-1) was inoculated directly into the distribution system. Coliform organisms were not detected in any samples taken downstream of the inoculation point. By comparison, laboratory jar tests showed low level survival for coliforms at the same chloramine residuals (0.3 mg l-1) for up to 48 h. In the second series of experiments, a by-pass pipe in the experimental distribution system was isolated, drained, and filled with tertiary treated effluent (10(3)-10(4) coliforms ml-1) to simulate the conditions in a dead-end. Coliform numbers were monitored and found to decrease rapidly, but they were still detectable at low levels after 7 weeks. The water in the by-pass section was then released into the main pipe-rig and sampled downstream. No coliforms were detected in water samples or in samples swabbed from the pipe walls. Finally, the flow in the main pipe-rig and in the by-pass was increased to dislodge any deposits and biofilm into the water. The absence of coliforms in any water samples taken during or after the flow increases is contrary to the widely accepted understanding that coliforms survive and grow in biofilms on pipe walls.     

Enhanced biodegradation of methoxychlor in soil under sequential environmental conditions.

Ring-U-[14C]methoxychlor [1,1-bis(p-methoxyphenyl)-2,2,2-trichloroethane] was incubated in soil under aerobic and anaerobic conditions. Primary degradation of methoxychlor occurred under anaerobic conditions, but not under aerobic conditions, after 3 months of incubation. Analysis of soil extracts, using gas chromatography, demonstrated that only 10% of the compound remained at initial concentrations of 10 and 100 ppm (wt/wt) of methoxychlor. Evidence is presented that a dechlorination reaction was responsible for primary degradation of methoxychlor. Analysis of soils treated with 100 ppm of methoxychlor in the presence of 2% HgCl2 showed that 100% of the compound remained after 3 months, indicating that degradation in the unpoisoned flasks was biologically mediated. Methanogenic organisms, however, are probably not involved, as strong inhibition of methane production was observed in all soils treated with methoxychlor. During the 3-month incubation period, little or no evaluation of 14CO2 or 14CH4 occurred under either aerobic or anaerobic conditions. Cometabolic processes may be responsible for the extensive molecular changes which occurred with methoxychlor because the rate of its disappearance from soil was observed to level off after exhaustion of soil organic matter. After this incubation period, soils previously incubated under anaerobic conditions were converted to aerobic conditions. The rates of 14CO2 evolution from soils exposed to anaerobic and aerobic sequences of environments ranged from 10- to 70-fold greater than that observed for soils exposed solely to an aerobic environment.     

农田生态系统中除草剂阿特拉津的环境行为及其模型研究进展

阿特拉津是世界范围内广泛使用的除草剂,在曾经使用阿特拉津的国家的地下水、河流和湖泊中已经检测到阿特拉津的残留,长期暴露在该有机污染物的环境中,势必对动物的生殖与繁衍及人体的健康产生不良影响。介绍了阿特拉津国内外的研究情况,着重评述了阿特拉津的吸附机制与影响因素、化学降解、生物降解、生态毒理学评价以及模型对其环境行为的描述,目的旨在帮助理解田间阿特拉津迁移机制及其如何污染地下水。农田生态系统中阿特拉津的迁移规律决定其环境行为,它是进行环境和健康风险评价的基础,目前应用较多的迁移模型是经典的对流-扩散方程,该模型已广泛运用于水-土系统中化学物质的迁移,且室内模拟的实验结果能较好解释田间现象,因此,开展阿特拉津在稳定流场饱和/非饱和室内土柱中的混合置换实验及批量平衡吸附实验,可获得反映阿特拉津迁移的穿透曲线特性及阿特拉津吸附性能的分配系数,结合数学模型拟合阿特拉津在土壤中非平衡迁移曲线,用拟合参数预测不同深度土壤中阿特拉津浓度变化和累积淋溶量动态规律,应该是今后研究工作的重点。     

Inducible cell lysis system for the study of natural transformation and environmental fate of DNA released by cell death.

Two novel conditional broad-host-range cell lysis systems have been developed for the study of natural transformation in bacteria and the environmental fate of DNA released by cell death. Plasmid pDKL02 consists of lysis genes S, R, and Rz from bacteriophage lambda under the control of the Ptac promoter. The addition of inducer to Escherichia coli, Acinetobacter calcoaceticus, or Pseudomonas stutzeri containing plasmid pDKL02 resulted in cell lysis coincident with the release of high amounts of nucleic acids into the surrounding medium. The utility of this lysis system for the study of natural transformation with DNA released from lysed cells was assessed with differentially marked but otherwise isogenic donor-recipient pairs of P. stutzeri JM300 and A. calcoaceticus BD4. Transformation frequencies obtained with lysis-released DNA and DNA purified by conventional methods and assessed by the use of antibiotic resistance (P. stutzeri) or amino acid prototrophy (A. calcoaceticus) for markers were comparable. A second cell lysis plasmid, pDKL01, contains the lysis gene E from bacteriophage phi X174 and causes lysis of E. coli and P. stutzeri bacteria by activating cellular autolysins. Whereas DNA released from pDKL02-containing bacteria persists in the culture broth for days, that from induced pDKL01-containing bacteria is degraded immediately after release. The lysis system involving pDKL02 is thus useful for the study of both the fate of DNA released naturally into the environment by dead cells and gene transfer by natural transformation in the environment in that biochemically unmanipulated DNA containing defined sequences and coding for selective phenotypes can be released into a selected environment at a specific time point. This will allow kinetic measurements that will answer some of the current ecological questions about the fate and biological potential of environmental DNA to be made.     

Hydra, a model system for environmental studies

Hydra have been extensively used for studying the teratogenic and toxic potential of numerous toxins throughout the years and are more recently growing in popularity to assess the impacts of environmental pollutants. Hydra are an appropriate bioindicator species for use in environmental assessment owing to their easily measurable physical (morphology), biochemical (xenobiotic biotransformation; oxidative stress), behavioural (feeding) and reproductive (sexual and asexual) endpoints. Hydra also possess an unparalleled ability to regenerate, allowing the assessment of teratogenic compounds and the impact of contaminants on stem cells. Importantly, Hydra are ubiquitous throughout freshwater environments and relatively easy to culture making them appropriate for use in small scale bioassay systems. Hydra have been used to assess the environmental impacts of numerous environmental pollutants including metals, organic toxicants (including pharmaceuticals and endocrine disrupting compounds), nanomaterials and industrial and municipal effluents. They have been found to be among the most sensitive animals tested for metals and certain effluents, comparing favourably with more standardised toxicity tests. Despite their lack of use in formalised monitoring programmes, Hydra have been extensively used and are regarded as a model organism in aquatic toxicology.     

抗生素的环境归宿与生态效应研究进展

抗生素是人类与动物疾病防治中被广泛使用的抑菌或杀菌药物。近年来,随着环境耐药性基因的出现,抗生素引起的环境问题成为公众关注的热点。关于抗生素的检测、环境行为和生态毒性等方面的研究也越来越多。综合已有的研究资料,对抗生素在环境中暴露水平、降解行为及其对生态环境影响等方面进行探讨,并对今后的研究进行展望。     

Sulfamethoxazole biodegradation and biotransformation in the water-sediment system of a natural river

In this study, the biodegradation of sulfamethoxazole (SMX) as affected by temperature, humic acid (HA) and SMX concentrations was investigated by HPLC-MS/MS analysis based on water-sediment batch experiments. The first order decay model (C = C₀ × exp (−kt)) was best fitted for SMX biodegradation. SMX degradation significantly increased with elevated temperature (degradation rate was 82.9% at 25 °C vs. 40.5% at 4 °C in sediment), HA contents (30 mg/L of HA facilitated SMX degradation rate at 90.1% vs. 82.9% by 5 mg/L of HA). However, SMX degradation is not readily dependent on its initial concentrations (1, 2, 20, 50 and 100 mg/L), which suggests a co-metabolism mechanism may involove in SMX biodegradation. The prevalence of Bacillus firmus and Bacillus cereus among the strains isolated and identified on the basis of 16s rDNA gene sequence implicates their potential efficiency at degrading SMX. Only less than 1% of the SMX was transformed into its metabolite N₄-acetyl-sulfamethoxazole, suggesting the need to pay more attention to the parent SMX. Overall, the ubiquitous occurrence of SMX underscores the need to explore better solutions for its removal and to mitigate this risk to public health.     

Significance of biological effects on phosphorus transformation processes at the water-sediment interface under different environmental conditions

This study investigated the significance of biological effect on phosphorus (P) transformation processes at the water-sediment interface, and the variations of biological effect under different conditions of pH, light, and temperature conditions were discussed. A customized integrated piece of equipment was designed and employed in the study in order to maintain the samples in situ. The results showed that the decrements of total P (TP) in sediment in the non-sterilized systems were 2-6 times higher than those in the systems sterilized by Co60γ-ray, which indicated that the biological activities strongly stimulated P release and its intensity could reach to over 5 times higher than that from the physico-chemical effect. In addition, the extent of biological effect was greatly affected by different environmental conditions. The organism biomass and biological effect was enhanced as temperature increased, but the variation trends of single colony contribution (SCC) were different among P fractions. Biological effect was strengthened and more P was released from the sediment under irradiation, as light was essential for the growth of algae and with the excessive absorption of P by algae. pH was detected to have no major effect on bacterial biomass and P cycling, but higher pH was propitious to the decomposition of organic P (OP). Results obtained from this investigation clarified the understanding of P biogeochemical cycling and eutrophication occurrence mechanism in the lake system.     

An environmental evaluation of mechanical systems using environmentally acceptable refrigerants

New hydrofluorocarbon refrigerant gases in domestic refrigerators require the use of the newly developed synthetic lubricants. Research carried out so far indicates that the hermetic compressor used in these refrigerating systems is one component that is likely to be directly influenced by this change in working fluid. This may affect system performance as well as system durability such that a potential environmental improvement may result in a shift in environmental pollution. An environmental evaluation, using a life cycle assessment (LCA) computational tool, is carried out to study the influence of the individual components on the overall product environmental contribution. The manufacture and the recovery of the refrigerants addressed in this study were also included in this evaluation. In this LCA study, the hermetic compressor was found to contribute significantly to a number of impact categories as compared to other product components of concern. This becomes of primal environmental significance in view of the possibility that tribological characteristics, due to the presence of the new refrigerant/lubricant combinations, may influence its performance.     

An in vitro study of implant--tooth-supported connections using a robot test system.

Many unsolved problems in dental implant research concern the interfacial stress distributions between the implant components, as well as between the implant surface and contacting bone. To obtain a mechanical understanding of how vertical and horizontal occlusal forces are distributed in this context, it is crucial to develop in vitro testing systems to measure the force transmission between dental implants and attached prostheses. A new approach to such testing, involving a robotic system, is described in this investigation. The system has been designed to produce simulated mandibular movements and occlusal contact forces so that various implant designs and procedures can be thoroughly tested and evaluated before animal testing or human clinical trials. Two commonly used fixed prosthesis designs used to connect an implant and a tooth, a rigid connection and a nonrigid connection, were fabricated and used for experimental verification. The displacement and force distributions generated during simulated chewing activities were measured in vitro. Force levels, potentially harmful to human bone surrounding the connected dental implant and tooth, were analyzed. These results are useful in the design of prostheses and connecting components that will reduce failures and limit stress transfer to the implant/bone interface.     

An improved method for the study of apoptosis-related genes using the tet-on system

Inducible gene expression systems are particularly useful for the functional characterization of genes with putative toxic properties. In the course of studying the role of hypoxia-regulated gene expression on cell survival using the tetracycline-inducible (tet-on) system, the author noted that exposure to the inducing ligand doxycycline (dox) inhibited caspase-3 cleavage in control samples. To limit this confounding off-target effect, he devised an in vitro pulse dose, delayed-injury protocol testing both dox and a novel tetracycline analog 9-t-butyl doxycycline (9-TB). Although 9-TB induced higher transgene levels compared to matched concentrations of dox, continuous exposure to both drugs inhibited caspase-3 cleavage in hypoxic samples. Conversely, a 6-h pulse dose of 9-TB followed by a 40-h washout period prior to hypoxic challenge activated robust transgene expression and lessened the inhibitory effects on caspase-3 processing. It is anticipated that these protocol modifications will improve the performance of tet-regulated genetic screens, particularly in situations where cell death is used as a primary end point.     

An automatic system to study the responses of respiration and photosynthesis by submerged macrophytes to environmental variables

An apparatus to measure the rates of respiration and photosynthesis of aquatic plants in water at velocities of up to 200 mm s^–1 in a closed water-flow system with partial recirculation, is described. The temperature, the light regime and the concentration of dissolved oxygen are controlled automatically. Typical results are given for Ranunculus penicillatus var. calcareus which were repeatable between the same season in different years and compared with published data.     

Pyrithiones as antifoulants: environmental fate and loss of toxicity

The environmental fate and the loss of toxicity of two important antifouling actives, zinc pyrithione (ZnPT) and copper pyrithione (CuPT), were investigated using a bioassay study and an outdoor microcosm study. The bioassay used inhibition of the growth of a marine diatom (Amphora coffeaeformis) to measure the toxicity of ZnPT and CuPT over time in sterile, natural, and sediment-supplemented seawater. In natural seawater and sediment-supplemented seawater in the dark and in sterile seawater exposed to light, growth inhibition was reduced at rates corresponding to the rapid degradation rates for ZnPT and CuPT measured in previous aquatic metabolism, die-away, and photolysis studies. Similarly, the bioassay results from sterile seawater in the dark were consistent with the slower degradation rates measured in abiotic hydrolysis studies. In addition to corroborating the rapid degradation of pyrithione upon exposure to light or sediment, the loss of toxicity indicated that the degradation products were not toxic at the concentrations produced from the dose, which was much higher than predicted environmental concentrations. To supplement environmental fate studies designed to elucidate single-pathway transformations, a microcosm study was conducted to integrate all of the degradation pathways. The study used two sediment and water systems, one of which was dosed during the day and the other at night. The pyrithione degraded rapidly in the water phase, with very little accumulation in the sediment. 2-Pyridine sulfonic acid (PSA) and carbon dioxide were the only detectable degradation products 30 d after dosing. Aquatic toxicity studies with PSA showed no observable effect at concentrations at least three orders of magnitude higher than those for either ZnPT or CuPT. As a result, the worst-case environmental concentration of PSA is expected to be far below the no observable effect concentration.     

Investigation of the fate of Sry-expressing cells using an in vivo Cre/loxP system

Sry (sex-determining region on Y chromosome) is expressed in the undifferentiated, bipotential genital ridges of mammalian XY fetuses. The expression of Sry initiates testis development, but the lineage of Sry-expressing cells is unclear. In this study, double-transgenic mice were analyzed using the Cre/loxP system. Cre under the control of the Sry promoter was expressed in the fetal gonads of transgenic mice similarly to endogenous Sry. The Sry/Cre-transgenic mice were crossed with CAG(cytomegalovirus immediate-early enhancer, chicken beta-actin promoter and fusion intron of chicken beta-actin and rabbit beta-globin)/loxP/CAT/loxP/LacZ-transgenic mice, in which the transgene expressed beta-galactosidase after a Cre-mediated recombination event. Sertoli cells, germ cells of testes and granulosa cells of ovaries of double-transgenic mice stained positive with X-gal. Cre expression was detected in germ cells and peritubular/Sertoli cells in adult testes. It is not clear whether beta-galactosidase expression in the Sertoli cells of the testes occurred as a result of Cre expression in the adult or in the fetal gonads. These analyses indicate that cells expressing Sry-inducing factors in female fetal gonads become granulosa cells.     

An environmental study of Silurian atrypid communities from southern Norway

Atrypid communities are described from the Silurian succession of southern Norway. These atrypids show striking variation in their mode of occurrence, several features of which are described quantitatively. Mature, well-developed communities occur in calcareous rocks which were apparently deposited in a well-aerated shallow environment. Stunted communities (identified by small shell size despite maturity) occur in carbonate-poor sediments deposited in deeper and less turbulent environments. Other communities are composed of immature shells which were apparently killed by a catastrophic event. Communities are also seen in which catastrophe was not total, and survivors can be recognised. The atrypid niche was taken over by other animal communities when major environmental changes took place.     

The environmental toxicity of crassin acetate using Tetrahymena pyriformis as a model

Crassin acetate, a macrocyclic diterpene lactone, may constitute as much as 1.5% of the dry weight of the cortex of the gorgonian Pseudoplexaura porosa (Houttuyn). However, physiological activity of this compound has not been demonstrated. Amicronucleate Tetrahymena pyriformis were used to establish that crassin acetate does possess physiological activity. The effects of this compound are essentially concentration dependent and for concentrations of 0.027 to 0.133 mM, they may be summarized as follows: increased generation time from 0 to 14 hours after subculture; decreased population density; decreased motility; and death. The conclusions of this investigation have been extended to include a possible role of the macrocyclic diterpenes in their natural environment, i. e., crassin acetate and related compounds function in the marine ecosystem by decreasing the viability of ciliated larvae of organisms which compete with the gorgonians for space.     

Investigating the genetic architecture of conditional strategies using the environmental threshold model

The threshold expression of dichotomous phenotypes that are environmentally cued or induced comprise the vast majority of phenotypic dimorphisms in colour, morphology, behaviour and life history. Modelled as conditional strategies under the framework of evolutionary game theory, the quantitative genetic basis of these traits is a challenge to estimate. The challenge exists firstly because the phenotypic expression of the trait is dichotomous and secondly because the apparent environmental cue is separate from the biological signal pathway that induces the switch between phenotypes. It is the cryptic variation underlying the translation of cue to phenotype that we address here. With a ‘half-sib common environment’ and a ‘family-level split environment’ experiment, we examine the environmental and genetic influences that underlie male dimorphism in the earwig Forficula auricularia. From the conceptual framework of the latent environmental threshold (LET) model, we use pedigree information to dissect the genetic architecture of the threshold expression of forceps length. We investigate for the first time the strength of the correlation between observable and cryptic ‘proximate’ cues. Furthermore, in support of the environmental threshold model, we found no evidence for a genetic correlation between cue and the threshold between phenotypes. Our results show strong correlations between observable and proximate cues and less genetic variation for thresholds than previous studies have suggested. We discuss the importance of generating better estimates of the genetic variation for thresholds when investigating the genetic architecture and heritability of threshold traits. By investigating genetic architecture by means of the LET model, our study supports several key evolutionary ideas related to conditional strategies and improves our understanding of environmentally cued decisions.