No description available.

Bacterial communities are attractive indicators of environmental impact because they live in molecularly intimate association with their habitat and can respond rapidly to change. There are though, still substantial difficulties describing bacterial communities, and relating the data collected to ecological factors. In soils for example, there is a lack of association between bacterial divefOity and soil function. .. There is within microbiology a fascination with the rare species present in many habitats. However, most ecosystem activity will reside with the dominant species performing that class of activity. So, for example, most carbon turnover will be carried out by the dominant heterotrophs. Modern molecular methods provide data capable of describing the dominant bacterial populations in environmental samples. As a consequence of widespread use of these methods, there is no shortage of molecular data, but there is a shortage of concepts to adequately understand and exploit these data. In this thesis, a multi-disciplinary approach, combining classical ecology, and molecular microbial community analysis, was used to show for the first time that bacterial community responses to perturbation can be used as a metric for ecological risk assessment. I ,. demonstrated in this thesis that microbial communities in perturbed and control environments were fundamentally different at the level of community structure. This simple property of bacterial communities, combined with a simple and robust statistical measure provides clear criteria for determining an adverse effect. Thus bacteria may potentially be exploited as surrogates for higher organisms, by regulators seeking a generally applicable assessment of anthropogenic impact. Rank abundance analysis may also provide a measure of recovery as the effects of perturbation are ameliorated over time. This may be of particular relevance at sites where remedial treatment is being carried out since it is the microbial communities that are responsible for degrading pollutants in the environment and are thus key determinants of ecosystem health in contaminated environments.

No description available.

No description available.

No description available.

As a widely studied and convenient model organism, C. elegans could be a useful tool in the investigation of in vivo metabolism.' A clear understanding ·of the molecular response to chemical exposure is required across a broad range of disciplines, from pharmacology to pesticide development. B-naphthoflavone, chloroquine, dazomet, imidacloprid, juglone and thiabendazole were selected for study. Touch respons~ assays were employed to monitor the responses of wild-type C. elegans to. different concentrations of chemical over 72 hours and the associated transcriptional response was analysed by whole genome microarray. Populations exposed to the six chemicals over 1 hour and 48 hours were compared to those subjected to osmotic and thermal stress, as well as to unstressed controls. Concerted changes' in the C. elegans transcriptome occur in response to exposure to specific chemicals. A large proportion of responsive genes encode enzymes with a known metabolic role, some with human homologues, predominantly cytochrome P450s, glutathione S-tranferases and UDPglucuronosyltransferases. Genes that encode nuclear hormone receptors and signalling molecules were also up-regulated, and future research will reveal whether they have a role in mediating the response to xenobiotic exposure. Other genes identified included nematode-specific genes, and genes of unknown function with mammal{an homologues. Genes ,encoding the antimicrobial thaumatins and caenacins were up-regulated in response to xenobiotic exposure. Others of the up-regulated genes encode signalling molecules that have been shown to coordinate responses to biotic stress. Taken together these results suggest that there is overlap between the responses to biotic and xenobiotic challenge. A green fluorescent C. elegans reporter strain was produced that describes . the cellular location of the up-regulation of cyp-35A5 by p- naphthoflavone and thiabendazole. This proof of principle provides the potential for panels of such reporters to be used in further investigations of meta,bolism of xenobiotic compounds in C. elegans.

Technetium and uranium are radionuclides found in groundwaters at sites where nuclear wastes have been processed or stored. As a result, increasing understanding of the mobility of these radioactive contaminants in the environment is required in order to predict their movement in the sub-surface and to develop efficient remediation of contaminated environments. The redox chemistry of both technetium and uranium exerts a strong control on their environmental behaviour. Unde~ oxic conditions, mobile Tc(VII) and U(VI) species dominate. In contrast, under reducing conditions the Tc(IV) and U(IV) oxidation states predominate and are poorly soluble. A change in oxidation state of both Tc and U can be effected by indigenous microbial activity in natural soils and sediments. As a result, indigenous microbes may play an important role in controlling the environmental behaviour of both these redox active radionuclides. Here, a multidisciplinary approach is applied in order to identifY biogeochemical factors that control the redox state and environmental behaviour of Tc and U in soil from the UKAEA operated site at Dounreay, UK. Microcosm experiments containing soil from the site' at Dounreay showed that indigenous microbial activity caused removal of Tc(VII) from solution during anaerobic incubation and was most likely mediated by '~'-------abiotic~reauCtiori-of-Tc(VII)-wiih microbially -pro-dilced---Fe(II).--X,:ray -absc)rptiori--------------- spectroscopy (XAS) analysis confirmed reduction of Tc(VII) to Tc(IV) in microcosm experiments. Tc was found to be partially remobilised following exposure of reduced Tc(IV)-labelled soils to _air, but was not significantly remobilised following exposure to nitrate. In uranium experiments, uptake of U(VI) by soil was rapid and complete under oxic conditions from artificial groundwater and in experiments with groundwater amended with ethylenediaminetetraacetic acid (EDTA). By contrast, uptake was slower in systems amended with bicarbonate. XAS experiments confirmed that uranium was adsorbed to soil as U(VI) in all three groundwater systems. After anaerobic. incubation for 120 days and the development of microbially-mediated Fe(III)- and sol- reducing conditions, XAS analysis showed that soil-associated uranium was present as U(IV) in all three systems. Further investigation of unamended artificial groundwater systems indicated that reduction of sorbed U(VI) required an active microbial population. These findings suggest that indigenous soil microorganisms in a Dounreay-type soil environment will exert a strong control on the fate ofTc and U.

No description available.

Packaging films are an inevitable aspect of the modem societies. This is especially so in the food containment industry. These days most of the packaging films that are available in the market are made from polyolefmic materials. Although these materials perform superior package functions, they are riot biodegradable. This is a cause of concern for the environment. Unlike polyolefinic packaging, packaging made from regenerated cellulose films are biodegradable because of their cellulosic source. However, modification of these films to deliver suitable packaging functions could compromise the biodegradability of these films. The application of an impemieable thermoplastic coating, . of colorants and the use ofplasticizers are among the modifications that interfer~with the biodegradability of the regenerated cellulose packaging. The influence of several factors on the biodegradation behaviour of different types of coated and uncoated cellophane films was studied in this research. Two general approaches were undertaken for this study. Firstly, the influence of a specific colour reducing bacterium, Shewanella strain JI8 143, on coated regenerated cellulose films, in the presence and in the absence of colorant materials, was investigated. Secondly, microorgamsms that are capable of degrading various coated and uncoated regenerated cellulose films were enriched from landfill soil inocula. Degradation behaviour of each film was then studied using the cultivated culture. Several. analytical techniques were used to establish the changes that were induced into the treated regenerated cellulose. films. Techniques such as UV spectrophotometry, FTIR spectrop40tometry, contact angle measurement, SEM analysis, differential scanning calorimetry and gas chromatography were used. A number of molecular biology approaches such as the polymerase chain reaction (peR) procedure and restriction enzyme digestion were undertaken to an~lyse the community profile ofthe enriched culture. Evidence is given to show that the nitrocellulose coating underwent denitrification when treated with Shewqnella 118 143 culture in the presence of azo dye. However, poly(vinylidene chloride) coating incubated with Shewanella 118 143 culture did not undergo any significant chemical changes either in the· presence or in the absence of azo dye. The enrichment study, based on the biodegradation of various regenerated cellulose films, indicated that the biodegradation rate of cellulosic films was greater under anaerobic conditions than under aerobic conditions. The enrichment provides a number of c·ultures that are capable of utilising cellophane films as a carbon source, under anaerobic conditions. Activities of both bacteria and methanogenic archaea were observed in all of the enriched cultures. Profiling bacterial community ofthe enriched cultures gave general information concerning the way these enriched cultures are related.

Sampling of airborne particle number concentrations was carried out in roadside locations in Leicester and Manchester, UK. A DMS500 was used to measure particle size distributions betWeen 4.87 and lOOOnm in both locations and a lognoimal fitting procedure was used :to model the modal parameters present within the size distributions across the diurnal cycle. For the most part, five modes were found to best describe the diurnal hourly averaged number size distributions in both locations. Two modes were found to exist below approximately 20nm, and were termed nucleation modes. These were believed to arise from primary and secondary sources, predominantly consisting of externally mixed liquid aerosol particles. These were thought to have arisen from binary and ternary nucleation ofprecursor gases such as, NOx, SOx and NH3, or through photochemically induced nucleation of organic species, especially aromatics arising from vehicle exhaust. Also the condensation of unburnt fuel may contribute to these modes~ Two further modes were found to exist between approximately 20nm and 150nm and were termed Aitken modes. These were believed to consist predominantly of \. internally mixed particles, have a solid core with a coating of organic and inorganic compounds arising as a direct vehicle exhaust emission. A much smaller mode which generally contributed less than 5% to total number concentrations, termed the accumulation mode, was found to exist >150nm and was likely to have arisen due to agglomeration of smaller Aitken mode particles. Both nucleation and Aitken mode number concentrations shared strong correlations with traffic flow during free-flow conditions. The relationship was seen to break down during busier traffic conditions, when often lower particle concentrations occ~rred, likely due to reduced vehicle speeds during such times. The Aitken mode particle count shared a strong decay relationship with wind speed in both locations, whilSt no relationship was seen between the nucleation mode count and wind speed in Manchester and only a weak decay relationship was seen in Leicester. This is likely due to the competition between existing Aitken mode particle counts and nucleation (new) particle formation. The absence of a relationship between nucleation' mode and wind speed in Manchester is thought to have been the case since new particle formation from gaseous precursors balanced dilution and dispersion occurring as aresult of increased wind speed. The weak decay relationship seen in the Leicester roadside location may have resulted due to scavenging ofgaseous precursors responsible fOf new particle formation at this locatio~ due to higher preexisting concentrations. Short time scale measurements of particle counts in Leicester showed the transient nature of particle concentrations in the roadside environment, with particle counts on a second by seCond basis often an order ofmagnitude higher than the 3 minute mean concentration. At times during each hour, these excursions, especially for the Aitken mode, were found to contribute up to one fifth to total hourly particle counts and yet only lasted for a few minutes in total during each hour. The Aitken mode particles dominating these excursions are thought to be more biologically persistent than the nucleation mode particles, ~eing able to pe~etrate deep into the lung carrying a range oftoxic inorganic and organic compounds. A high volume sampler was used to collect size segregate particulate matter at a roadside location in Leeds, UK. Four size fractions below l0J.lm, including ultrafines were analysed for a range oftrace elements present using a sequential extraction scheme. Elements predominantly distributed within the fmer particles (<2.5J.lffi) included Pb, V, Rh, Ti, K, Ni, Si, rn: Pt, Se, Cr, Co, Pd, Ce, Ag and La, whilst elements predominantly distributed within the coarser size fractions (> IJ.lm) included Mg, Mn, AI, Cu, ~a, Ba, Fe, and Ca Most elements within the ultrafine size fraction were found to be larg~ly insoluble. Ni was found to be present Within PMIO at concentrations which may result in an increased excess lifetime risk of carcinogenic effects. Fe was one of the most insoluble elements found in the ultrafine size fraction, which was indicative of the type of Fe present in this size fraction, Fe3+, which is responsible for ... driving redox reactions in the lung ~hich can ultimately result in inflammation through oxidative stress. A significant amount of Pb was present within the size fraction between 0.1 and IJ.lm, likely arising due to a comb.ination of lead deposited in roadside soils from previous leaded gasoline use and long range transport from industrial sources. Additionally, a further potential source of Pb is from weights used to balance vehicle wheels which are deposited and ground up by passing vehicles.