El léxico y el tema del amor en Las Traquinias de Sófocles

Sin resume

A multi-disciplinary approach to the characterization of waterlogged burial environments : assessing the potential for the in situ preservation of organic archaeological remains

The aim of this study was to characterise waterlogged burial environments and to assess their potential for the in situ preservation of organic archaeological remains. To characterise these environments, environmental parameters were monitored through the soil profile and integrated with a study of the composition and activity of the microbial community.Soil cores were taken from two wetland sites located in the Humberhead Levels in Yorkshire: Hatfield Moor and Sutton Common. Cores were subsampled at depth intervals down to 100 cm depth, to allow for the examination of the vertical distributions of the variables being studied. Redox potential, water level variation and other physico-chemical parameters were measured down the soil profile. Bacterial abundance was determined by direct counts; activity was assayed by extracellular enzyme activity and leucine assimilation. The physiological profile of the microbial community was analysed using BIOLOG and the bacterial community structure was examined by PCR-DGGE.Redox potential readings were positive above the water table and negative below. The bacterial abundance and activity were greatest at the soil surface and, in general, decreased with depth. BIOLOG showed both depth variation and between site variation in microbial physiological profile. DGGE gels presented a different bacterial community structure with depth and between-sites.The results from monitoring of redox potential combined with water table height and determination of bacterial abundance and activity allowed the recognition of stratigraphic horizon where there was less potential for microbial degradation of organic archaeological artefacts. The information from BIOLOG and DGGE holds the potential for the development of a more subtle understanding of between-depth and between-site differences in the degradation process.The physico-chemical and the conventional and molecular microbiological results presented in this thesis have shown that microbial activity is implicated as a key factor that could lead to compromised in situ preservation conditions at the sites studied

Bacterial community dynamics during the early stages of biofilm formation in a chlorinated experimental drinking water distribution system: implications for drinking water discolouration

Aims : To characterize bacterial communities during the early stages of biofilm formation and their role in water discolouration in a fully representative, chlorinated, experimental drinking water distribution systems (DWDS). Methods and Results : Biofilm development was monitored in an experimental DWDS over 28 days; subsequently the system was disturbed by raising hydraulic conditions to simulate pipe burst, cleaning or other system conditions. Biofilm cell cover was monitored by fluorescent microscopy and a fingerprinting technique used to assess changes in bacterial community. Selected samples were analysed by cloning and sequencing of the 16S rRNA gene. Fingerprinting analysis revealed significant changes in the bacterial community structure over time (P < 0·05). Cell coverage increased over time accompanied by an increase in bacterial richness and diversity. Conclusions : Shifts in the bacterial community structure were observed along with an increase in cell coverage, bacterial richness and diversity. Species related to Pseudomonas spp. and Janthinobacterium spp. dominated the process of initial attachment. Based on fingerprinting results, the hydraulic regimes did not affect the bacteriological composition of biofilms, but they did influence their mechanical stability. Significance and Importance of the Study : This study gives a better insight into the early stages of biofilm formation in DWDS and will contribute to the improvement of management strategies to control the formation of biofilms and the risk of discolouration

Influence of hydraulic regimes on bacterial community structure and composition in an experimental drinking water distribution system

Microbial biofilms formed on the inner-pipe surfaces of drinking water distribution systems (DWDS) can alter drinking water quality, particularly if they are mechanically detached from the pipe wall to the bulk water, such as due to changes in hydraulic conditions. Results are presented here from applying 454 pyrosequencing of the 16S ribosomal RNA (rRNA) gene to investigate the influence of different hydrological regimes on bacterial community structure and to study the potential mobilisation of material from the pipe walls to the network using a full scale, temperature-controlled experimental pipeline facility accurately representative of live DWDS. Analysis of pyrosequencing and water physico-chemical data showed that habitat type (water vs. biofilm) and hydraulic conditions influenced bacterial community structure and composition in our experimental DWDS. Bacterial community composition clearly differed between biofilms and bulk water samples. Gammaproteobacteria and Betaproteobacteria were the most abundant phyla in biofilms while Alphaproteobacteria was predominant in bulk water samples. This suggests that bacteria inhabiting biofilms, predominantly species belonging to genera Pseudomonas, Zooglea and Janthinobacterium, have an enhanced ability to express extracellular polymeric substances to adhere to surfaces and to favour co-aggregation between cells than those found in the bulk water. Highest species richness and diversity were detected in 28 days old biofilms with this being accentuated at highly varied flow conditions. Flushing altered the pipe-wall bacterial community structure but did not completely remove bacteria from the pipe walls, particularly under highly varied flow conditions, suggesting that under these conditions more compact biofilms were generated. This research brings new knowledge regarding the influence of different hydraulic regimes on the composition and structure of bacterial communities within DWDS and the implication that this might have on drinking water quality

A methodological proposal to investigate the long term storage of pollutants in freshwater sediment biofilms and their response to environmental disturbances.

This research will review novel methodologies for understanding the behaviour of microbial communities and their role in pollution storage. Freshwater sediments are inhabited by attached microbial communities (biofilms) which are responsible for the majority of a river's metabolic activity. Biofilms thus provide valuable information on the environmental quality of the river and its surrounding areas. Despite remediation of freshwater sediments, biofilms can still store large quantities of pollutants. Biofilms have the exceptional capacity to adjust to new conditions including natural and anthropogenic environmental disturbances. Gaining a more comprehensive understanding of biofilm behaviour is therefore fundamental to developing improved management strategies. The initial focus of this research will be in the River Doe Lea in North East Derbyshire. The River Doe Lea extends 18km from the South at its source near Tibshelf, to the North at its discharge at the River Rother. In the 1990s the River was famed for having the highest level of dioxins in the world, 27 times higher than the second most polluted. The acute cause of this was a single pollutant event, however the river has also been subjected to long term anthropogenic pollution through industry, agriculture, transport (railways, M1) and wastewater pollution. While previous studies by the Environment Agency have focused on the flow, chemical, biological and ecological quality of the river, no research has been conducted into the role and behaviour of biofilms

Succession of bacterial and fungal communities within biofilms of a chlorinated drinking water distribution system

Understanding the temporal dynamics of multi-species biofilms in Drinking Water Distribution Systems (DWDS) is essential to ensure safe, high quality water reaches consumers after it passes through these high surface area reactors. This research studied the succession characteristics of fungal and bacterial communities un der controlled environmental conditions fully representative of operational DWDS. Microbial communities were observed to increase in complexity after one month of biofilm development but they did not reach stability after three months. Changes in cell numbers were faster at the start of biofilm formation and tended to decrease over time, despite the continuing changes in bacterial community composition. Fungal diversity was markedly less than bacterial diversity and had a lag in responding to temporal dynamics. A core-mixed community of bacteria including Pseudomonas, Massillia and Sphingomonas and the fungi Acremonium and Neocosmopora were present constantly and consistently in the biofilms over time and conditions studied. Monitoring and managing biofilms and such ubiquitous core microbial communities are key control strategies to ensuring the delivery of safe drinking water via the current ageing DWDS infrastructure

Understanding microbial ecology to improve management of drinking water distribution systems

Microorganisms in Drinking Water Distribution Systems (DWDS) and in particular the microbial communities that form biofilms on infrastructure surfaces, drive critical processes impacting water quality. This paper reviews knowledge, research approaches and monitoring methods to consolidate understanding of the microbial ecology of DWDS. The review highlights how microbial characteristics and subsequent behaviour can be broadly classified as common or complex. Common behaviour relates to the ubiquitous and continual development of biofilms, consistent core communities and mediated material accumulation. In contrast, the complex aspect relates to the shape, structure and composition of the microbiome, defined by site specific properties such as supplied source water, pipe material and hydraulic regimes. It is shown how the latest microbial tools and techniques can be applied to increase our understanding of DWDS ecology and how water utilities are starting to use this knowledge. This is not because of regulatory requirements, but in recognition that they provide valuable information facilitating pro-active management and operation benefits to these critical yet ageing systems, protecting water quality and public health in the process

Impact of phosphate dosing on the microbial ecology of drinking water distribution systems: fieldwork studies in chlorinated networks

Phosphate is routinely dosed to ensure regulatory compliance for lead in drinking water distribution systems. Little is known about the impact of the phosphate dose on the microbial ecology in these systems and in particular the endemic biofilms. Disturbance of the biofilms and embedded material in distribution can cause regulatory failures for turbidity and metals. To investigate the impact of phosphate on developing biofilms, pipe wall material from four independent pipe sections was mobilised and collected using two twin-flushing operations a year apart in a chlorinated UK network pre- and post-phosphate dosing. Intensive monitoring was undertaken, including turbidity and water physico-chemistry, traditional microbial culture-based indicators, and microbial community structure via sequencing the 16S rRNA gene for bacteria and the ITS2 gene for fungi. Whole metagenome sequencing was used to study shifts in functional characteristics following the addition of phosphate. As an operational consequence, turbidity responses from the phosphate-enriched water were increased, particularly from cast iron pipes. Differences in the taxonomic composition of both bacteria and fungi were also observed, emphasising a community shift towards microorganisms able to use or metabolise phosphate. Phosphate increased the relative abundance of bacteria such as Pseudomonas, Paenibacillus, Massilia, Acinetobacter and the fungi Cadophora, Rhizophagus and Eupenicillium. Whole metagenome sequencing showed with phosphate a favouring of sequences related to Gram-negative bacterium type cell wall function, virions and thylakoids, but a reduction in the number of sequences associated to vitamin binding, methanogenesis and toxin biosynthesis. With current faecal indicator tests only providing risk detection in bulk water samples, this work improves understanding of how network changes effect microbial ecology and highlights the potential for new approaches to inform future monitoring or control strategies to protect drinking water quality

Dynamics of biofilm re-growth in drinking water distributions systems

The majority of biomass within water distribution systems is in the form of attached biofilm. This is known to be central to drinking water quality degradation following treatment yet little understanding of the dynamics of these highly heterogeneous communities exists. This paper presents original information on such dynamics with findings demonstrating patterns of material accumulation, seasonality and influential factors. Rigorous flushing operations repeated over a one-year period on an operational, chlorinated system in the UK are presented. Intensive monitoring and sampling were undertaken including time series turbidity and detailed microbial analysis using 16S rRNA Illumina MiSeq sequencing. Results show bacterial dynamics were influenced by differences in the supplied water and by the material remaining attached to the pipe wall following flushing. Turbidity, metals and phosphate were the main factors correlated with the distribution of bacteria in the samples. Coupled with the lack of inhibition of biofilm development due to chlorine residual, this suggests that limiting inorganic nutrients, other than organic carbon, might be a viable component in treatment strategies to manage biofilms. The research also showed that repeat flushing exerted beneficial selective pressure, thus also a viable advantageous biofilm management option. This work advances our understanding of microbiological processes in drinking water distribution systems and helps inform strategies to optimise asset performance. IMPORTANCE: This research provides with novel information regarding dynamics of biofilm formation in real drinking water distribution systems made of different materials. This new knowledge on microbiological process in water supply systems can be used to optimise the performance of the distribution network and to guarantee safe and good quality drinking water to consumers

The microbial ecology of a Mediterranean chlorinated drinking water distribution systems in the city of Valencia (Spain)

Drinking water distribution systems host extensive microbiomes with diverse biofilm communities regardless of treatment, disinfection, or operational practices. In Mediterranean countries higher temperatures can accelerate reactions and microbial growth that may increase aesthetic water quality issues, particularly where material deposits can develop as a result of net zero flows within looped urban networks. This study investigated the use of flow and turbidity monitoring to hydraulically manage mobilisation of pipe wall biofilms and associated material from the Mediterranean city of Valencia (Spain). Pipe sections of different properties were subjected to controlled incremental flushing with monitoring and sample collection for physico-chemical and DNA analysis with Illumina sequencing of bacterial and fungal communities. A core microbial community was detected throughout the network with microorganisms like Pseudomonas, Aspergillus or Alternaria increasing during flushing, indicating greater abundance in underlying and more consolidated material layers. Bacterial and fungal communities were found to be highly correlated, with bacteria more diverse and dynamic during flushing whilst fungi were more dominant and less variable between sampling sites. Results highlight that water quality management can be achieved through hydraulic strategies yet understanding community dynamics, including the fungal component, will be key to maintaining safe and ultimately beneficial microbiomes in drinking water distribution systems