Autochthonous Microbial Communities Research Articles

Enhanced biodegradation of antibiotic combinations via the sequential treatment of the sludge resulting from pharmaceutical wastewater treatment using white-rot fungi Trametes versicolor and Bjerkandera adusta.

While anaerobic treatment is capable of treating pharmaceutical wastewater and removing antibiotics in liquid phases, solid phases may still contain significant amounts of antibiotics following this treatment. The main goal of this study was to evaluate the use of white-rot fungi to remove erythromycin, sulfamethoxazole, and tetracycline combinations from biosolids. The degradation potential of Trametes versicolor and Bjerkandera adusta was evaluated via the sequential treatment of anaerobic sludge. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analyses were used to identify competition between the autochthonous microbial communities and white-rot fungi. Solid-phase treatment using white-rot fungi substantially reduced antibiotic concentrations and toxicity in sludge. According to PCR-DGGE results, there is an association between species of fungus and antibiotic type as a result of the different transformation pathways of fungal strains. Fungal post-treatment of sludge represents a promising method of removing antibiotic combinations, therefore holding a significant promise as an environmentally friendly means of degrading the antibiotics present in sludge.

First insight into microbial diversity and ion concentration in the Uyuni salt flat, Bolivia

Abstract. The most important hypersaline environment in Bolivia is the Uyuni salt flat. It is the largest salt flat in the world and, it presents certain unique chemical characteristics and composition on its surface such as a gradient of ion concentrations from south to north. The autochthonous microbial communities in these salt flats have yet to be studied in detail, and it is not clear if these communities are somehow homogeneous across in the ca. 10,000 km2 flat. The present study was done in order to describe the structure of the microbial communities and determine any possible correlations with abiotic factors. Total DNA was extracted from rock salt samples obtained at different locations, and 16S rDNA followed by Terminal Restriction Fragment Length Polymorphism (T-RFLP) analyses. Statistical analyses of the communities indicated that the highest diversity indices were found in the southern area, and the microbial communities were clustered in three groups for bacteria and in two groups for archae...

Bioaugmentation with Novel Microbial Formula vs. Natural Attenuation of a Long-Term Mixed Contaminated Soil—Treatability Studies in Solid- and Slurry-Phase Microcosms

Treatability studies in real contaminated soils are essential to predict the feasibility of microbial consortium augmentation for field-scale bioremediation of contaminated sites. In this study, the biodegradation of a mixture of seven PAHs in a manufactured gas plant (MGP) soil contaminated with 3967 mg kg−1 of total PAHs using novel acid-, metal-tolerant, N-fixing, P-solubilizing, and biosurfactant-producing LMW and HMW PAH-degrading bacterial combinations as inoculums was compared in slurry- and solid-phase microcosms over natural attenuation. Bioaugmentation of 5 % of bacterial consortia A and N in slurry- and solid-phase systems enhanced 4.6–5.7 and 9.3–10.7 % of total PAH degradation, respectively, over natural attenuation. Occurrence of 62.7–88 % of PAH biodegradation during natural attenuation in soil and slurry illustrated the accelerated rate of intrinsic metabolic activity of the autochthonous microbial community in the selected MGP soil. Monitoring of the total microbial activity and population of PAH degraders revealed that the observed biodegradation trend in MGP soil resulted from microbial mineralization. In the slurry, higher biodegradation rate constant (k) and lower half-life values (t 1/2) was observed during bioaugmentation with consortium N, highlighting the use of bioaugmentation in bioslurries/bioreactor to achieve rapid and efficient bioremediation compared to that of a static solid system. In general, natural attenuation was on par with bioaugmentation. Hence, depending on the type of soil, natural attenuation might outweigh bioaugmentation and a careful investigation using laboratory treatability studies are highly recommended before the upscale of a developed bioremediation strategy to field level.

Bacterial diversity differences along an epigenic cave stream reveal evidence of community dynamics, succession, and stability.

Unchanging physicochemical conditions and nutrient sources over long periods of time in cave and karst subsurface habitats, particularly aquifers, can support stable ecosystems, termed autochthonous microbial endokarst communities (AMEC). AMEC existence is unknown for other karst settings, such as epigenic cave streams. Conceptually, AMEC should not form in streams due to faster turnover rates and seasonal disturbances that have the capacity to transport large quantities of water and sediment and to change allochthonous nutrient and organic matter sources. Our goal was to investigate whether AMEC could form and persist in hydrologically active, epigenic cave streams. We analyzed bacterial diversity from cave water, sediments, and artificial substrates (Bio-Traps®) placed in the cave at upstream and downstream locations. Distinct communities existed for the water, sediments, and Bio-Trap® samplers. Throughout the study period, a subset of community members persisted in the water, regardless of hydrological disturbances. Stable habitat conditions based on flow regimes resulted in more than one contemporaneous, stable community throughout the epigenic cave stream. However, evidence for AMEC was insufficient for the cave water or sediments. Community succession, specifically as predictable exogenous heterotrophic microbial community succession, was evident from decreases in community richness from the Bio-Traps®, a peak in Bio-Trap® community biomass, and from changes in the composition of Bio-Trap® communities. The planktonic community was compositionally similar to Bio-Trap® initial colonizers, but the downstream Bio-Trap® community became more similar to the sediment community at the same location. These results can help in understanding the diversity of planktonic and attached microbial communities from karst, as well as microbial community dynamics, stability, and succession during disturbance or contamination responses over time.

Polychlorinated biphenyl (PCB) anaerobic degradation in marine sediments: microcosm study and role of autochthonous microbial communities

Polychlorobiphenyl (PCB) biodegradation was followed for 1year in microcosms containing marine sediments collected from Mar Piccolo (Taranto, Italy) chronically contaminated by this class of hazardous compounds. The microcosms were performed under strictly anaerobic conditions with or without the addition of Dehalococcoides mccartyi, the main microorganism known to degrade PCBs through the anaerobic reductive dechlorination process. Thirty PCB congeners were monitored during the experiments revealing that the biodegradation occurred in all microcosms with a decrease in hepta-, hexa-, and penta-chlorobiphenyls (CBs) and a parallel increase in low chlorinated PCBs (tri-CBs and tetra-CBs). The concentrations of the most representative congeners detected in the original sediment, such as 245-245-CB and 2345-245-CB, and of the mixture 2356-34-CB+234-245-CB, decreased by 32.5, 23.8, and 46.7%, respectively, after only 70days of anaerobic incubation without any bioaugmentation treatment. Additionally, the structure and population dynamics of the microbial key players involved in the biodegradative process and of the entire mixed microbial community were accurately defined by Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) in both the original sediment and during the operation of the microcosm. The reductive dehalogenase genes of D. mccartyi, specifically involved in PCB dechlorination, were also quantified using real-time PCR (qPCR). Our results demonstrated that the autochthonous microbial community living in the marine sediment, including D. mccartyi (6.32E+06 16S rRNA gene copy numbers g(-1) sediment), was able to efficiently sustain the biodegradation of PCBs when controlled anaerobic conditions were imposed.

Coupling chemical oxidation and biostimulation: Effects on the natural attenuation capacity and resilience of the native microbial community in alkylbenzene-polluted soil

Coupling chemical oxidation with bioremediation could be a cost-effective system to cope with soil and groundwater pollution. However, the effects of chemical oxidation on autochthonous microbial communities are scarcely known. A detailed analysis that considers both the efficiency of the two technologies and the response of the microbial communities was performed on a linear alkylbenzene-polluted soil and groundwater samples. The impacts of a modified Fenton’s reaction (MFR) at various dosages and of permanganate on the microbiota over 4 weeks were assessed.The permanganate and MFR negatively affected microbial abundance and activity. However, the resilience of certain microbial populations was observed, with a final increase in potential hydrocarbon-degrading populations as determined by both the alkB gene abundance and the predominance of well-known hydrocarbon-degrading phylotypes such as Rhodococcus, Ochrobactrum, Acinetobacter and Cupriavidus genera as determined by 16S rRNA-based DGGE fingerprinting. The assessment of the chemical oxidant impact on autochthonous microbiota should be considered for the optimization of coupled field remediation technologies.

Fertilization and irrigation practice as source of microorganisms and the impact on nematodes as their potential vectors

The agricultural application of organic fertilizer as well as irrigation with partially treated wastewater is proposed to increase crop yield, but also the incidence of food borne pathogens. Studies have concentrated on the impact of such management practice on soil health, and on spread of pathogens during harvest, transport, and marketing, whereas the role of soil organisms in these processes was largely neglected. Therefore, the objective of the present work was to study microorganisms and nematodes as potential agents in suppression or dissemination of human pathogens. Two experimental field sites were established in semi-arid soils in the West Bank in Palestine. Treatments comprised application of fresh water, wastewater, sewage sludge and chicken manure in three successive crop cycles, and the effects on the microbial and nematode communities were assessed. Microbial biomass was generally fostered by all three organic amendments but the increase was dependent on arable site as well as the type of urban waste. The introduced microorganisms were able to establish in the field environment, indicating that the autochthonous microbial community was not effective in suppressing allochthonous enteropathogens. Nematodes, as potential bacterial vectors, displayed a population increase with organic input across crops and sites. Effects were most distinct by amendment with chicken manure, which additionally resulted in a decrease in diversity, with a distinct increase in bacterial-feeding r-strategists and strongly enriched food web conditions. In contrast, application of treated wastewater and sewage sludge fostered K-strategist, predominantly omnivores. This enhanced biomass at higher trophic levels indicates ample energy flux along the trophic cascade as well as a stable and structured food web, despite possible contaminants introduced via urban residues. The results highlight the potential role that soil biota play in governing soil responses to the application of biosolids and wastes in agricultural management practice.

Change of microbial community structure and functional gene abundance in nonylphenol-degrading sediment.

Biodegradation by autochthonous microbial community is an important way to clean up nonylphenol (NP) from contaminated river sediment. Knowledge of sediment microbial community can aid in our understanding of biological processes related to NP degradation. However, the change in sediment microbial community associated with NP biodegradation remains unclear. The present study investigated the shift in bacterial community structure and NP-degrading gene abundance in response to NP attenuation in river sediment. Sediment microcosms with different levels of 4-NP (0, 100, or 300 μg/g) were constructed. A nearly complete attenuation of NP occurred in the microcosm with 100 μg/g NP after 9 days' incubation, while a residual NP rate of 8.1 % was observed in the microcosm with 300 μg/g NP after 22 days' incubation. Illumina MiSeq sequencing analysis indicated that Gammaproteobacteria, Alphaproteobacteria, and Bacteroidetes predominated in NP-degrading river sediment. Sediment bacterial community structure varied significantly during NP biodegradation and subsequent incubation, which was affected by the level of added NP. The n-alkane biodegradation (alkB) gene abundance showed a significant variation in each NP-amended microcosm (100 or 300 μg/g), while a significant increase in the single component monooxygenase (sMO) gene abundance only occurred in the microcosm spiked with 300 μg/g NP. This study can provide some new insights toward NP-degrading microbial ecology in the environment.

Assessing impacts of unconventional natural gas extraction on microbial communities in headwater stream ecosystems in Northwestern Pennsylvania.

Hydraulic fracturing and horizontal drilling have increased dramatically in Pennsylvania Marcellus shale formations, however the potential for major environmental impacts are still incompletely understood. High-throughput sequencing of the 16S rRNA gene was performed to characterize the microbial community structure of water, sediment, bryophyte, and biofilm samples from 26 headwater stream sites in northwestern Pennsylvania with different histories of fracking activity within Marcellus shale formations. Further, we describe the relationship between microbial community structure and environmental parameters measured. Approximately 3.2 million 16S rRNA gene sequences were retrieved from a total of 58 samples. Microbial community analyses showed significant reductions in species richness as well as evenness in sites with Marcellus shale activity. Beta diversity analyses revealed distinct microbial community structure between sites with and without Marcellus shale activity. For example, operational taxonomic units (OTUs) within the Acetobacteracea, Methylocystaceae, Acidobacteriaceae, and Phenylobacterium were greater than three log-fold more abundant in MSA+ sites as compared to MSA− sites. Further, several of these OTUs were strongly negatively correlated with pH and positively correlated with the number of wellpads in a watershed. It should be noted that many of the OTUs enriched in MSA+ sites are putative acidophilic and/or methanotrophic populations. This study revealed apparent shifts in the autochthonous microbial communities and highlighted potential members that could be responding to changing stream conditions as a result of nascent industrial activity in these aquatic ecosystems.

Fe-oxide grain coatings support bacterial Fe-reducing metabolisms in 1.7-2.0 km-deep subsurface quartz arenite sandstone reservoirs of the Illinois Basin (USA).

The Cambrian-age Mt. Simon Sandstone, deeply buried within the Illinois Basin of the midcontinent of North America, contains quartz sand grains ubiquitously encrusted with iron-oxide cements and dissolved ferrous iron in pore-water. Although microbial iron reduction has previously been documented in the deep terrestrial subsurface, the potential for diagenetic mineral cementation to drive microbial activity has not been well studied. In this study, two subsurface formation water samples were collected at 1.72 and 2.02 km, respectively, from the Mt. Simon Sandstone in Decatur, Illinois. Low-diversity microbial communities were detected from both horizons and were dominated by Halanaerobiales of Phylum Firmicutes. Iron-reducing enrichment cultures fed with ferric citrate were successfully established using the formation water. Phylogenetic classification identified the enriched species to be related to Vulcanibacillus from the 1.72 km depth sample, while Orenia dominated the communities at 2.02 km of burial depth. Species-specific quantitative analyses of the enriched organisms in the microbial communities suggest that they are indigenous to the Mt. Simon Sandstone. Optimal iron reduction by the 1.72 km enrichment culture occurred at a temperature of 40°C (range 20–60°C) and a salinity of 25 parts per thousand (range 25–75 ppt). This culture also mediated fermentation and nitrate reduction. In contrast, the 2.02 km enrichment culture exclusively utilized hydrogen and pyruvate as the electron donors for iron reduction, tolerated a wider range of salinities (25–200 ppt), and exhibited only minimal nitrate- and sulfate-reduction. In addition, the 2.02 km depth community actively reduces the more crystalline ferric iron minerals goethite and hematite. The results suggest evolutionary adaptation of the autochthonous microbial communities to the Mt. Simon Sandstone and carries potentially important implications for future utilization of this reservoir for CO2 injection.

Consequences of anaerobic biotreatments of contaminated sediments on metal mobility

This study deals with anaerobic biotreatments of sediments contaminated with toxic metals carried out in slurry reactor. The sediment samples used for the investigation came from two Italian ports, and they were mainly contaminated with inorganic compounds (zinc, nickel and chromium). The treatments were aimed at assessing the responses of the autochthonous microbial community in relation to the geochemistry of the sediments (mainly organic carbon bioavailability) and the addition of organic and inorganic substrates. It was observed that the bio-available carbon in the sediments can greatly influence microbial growth but without a significant effect on metal mobilization. By contrast, the supply of inorganic nutrients to the sediments did not have a major effect on microbial growth although important changes in metal mobility were observed. Our results provide new insights on the effects of anaerobic biotreatments on changes in metal partitioning in contaminated sediments, highlighting that, under certain conditions, an increase of metals in the more mobile fractions can occur.

Effects of enhanced denitrification on hydrodynamics and microbial community structure in a soil column system

Enhanced heterotrophic denitrification by adding glucose was investigated by means of a soil column experiment which simulated the groundwater flow. The carbon-to-nitrogen ratio was the main factor determining denitrification potential under experimental conditions. The influence of stimulated denitrification on the autochthonous microbial community was investigated by quantitative PCR (qPCR), and denaturing gradient gel electrophoresis (DGGE). The qPCR detection of the nosZ genes encoding nitrous oxide reductase, and the comparison of the abundances of 16S rRNA genes revealed that the addition of glucose enhanced denitrification leading to an increase in both the total eubacteria and, in particular, in the ratio of denitrifying bacteria, which represented the 21% of the total native eubacteria on the basis of nosZ/16S rRNA gene ratio. Microbial community profiling by DGGE indicated that ribotypes closely related to the genera Acidovorax and Hydrogenophaga (Comamonadaceae family) became enriched in the soil column. The effects of biomass occurrence in the column system on soil hydrodynamics, assessed by tracer studies, revealed a reduction of porosity and a significant increase of dispersivity that could be caused by the appearance of new functional microbial biomass in the aquifer material under enhanced denitrifying conditions. The importance of investigating the microbial growth in relation to the hydrodynamic effects, during enhanced denitrification, has been revealed in the column system experiments associated with the bioremediation.Combining microbial characterisation and hydrodynamic data in a soil column system permits us to gain an insight to the limiting factors of different stimulation strategies that can be applied in the field.

Environmental Fate of Trifluralin, Procymidone, and Chlorpyrifos in Small Horticultural Production Units in Argentina

Pesticide biodegradation was studied in soil samples of a representative small periurban production unit (Moreno District, Argentina). The mean periods required for the 50 % dissipation of chlorpyrifos (16 days ± 1 day), procymidone (3.7 days ± 0.6 day), and trifluralin (3.6 days ± 0.6 day) were significantly lower than those measured for reference soil samples of a close location, using doses similar to the manufacturer’s recommendation. A preliminary screening scheme for pesticide-degrading bacteria on horticultural soil allowed the isolation of nine culturable bacterial strains, eight of which belonged to Pseudomonas genus. In order to consider the influence of the variability of soil properties on the biodegradation results, humidity, organic matter, conductivity, pH, water retention volume, density, respiration, and total phosphorous content were studied for different soil samples, finding no significant differences in the performed analysis. Overall, although the horticultural activity alters the natural soil, pesticide contamination effects could be reversed by the autochthonous microbial community.

Integrated modeling of biogeochemical reactions and associated isotope fractionations at batch scale: A tool to monitor enhanced biodenitrification applications

Enhanced in-situ biodenitrification (EIB) is a potential technology for remediating nitrate-polluted groundwater. EIB aims to create optimal biodenitrification conditions through the addition of carbon sources, enabling the autochthonous microbial community to degrade nitrate via different redox pathways. Biogeochemical numerical models are useful tools for predicting and designing such biodenitrification applications. Compound-specific stable isotope analysis (CSIA) is another valuable method for determining the degree of nitrate transformation. Therefore, incorporating isotope fractionation in biogeochemical models combines the two tools and is a key step in the development of reactive transport models of EIB under field conditions. In this work, we developed such an integrated model using the Phreeqc code and calibrated the model with batch scale experimental data using either ethanol or glucose as external carbon sources. The model included the following: microbiological processes —exogenous and endogenous nitrate respiration coupled to microbial growth and decay; geochemical processes —precipitation or dissolution of calcite; and isotopic fractionation —δ15N-NO3−, δ18O-NO3−, and δ13C-DIC, incorporating the full δ13C isotope geochemistry involved in EIB. The modeled results fit well with the hydrochemical and isotopic experimental data. The model also incorporated nitrite accumulation observed during the glucose experiment. The biogeochemical model indicates that, depending on the added carbon source, calcite precipitates (using ethanol) or dissolves (using glucose). In both cases, changes in hydraulic conductivity can be induced for actual and long-term EIB applications. The incorporation of isotope fractionation in the model better enables to account for other natural attenuation processes, such as dilution and dispersion, in EIB applications at field scale. Both calibrated enrichment factors (+8‰ for ethanol and +17‰ for glucose) suggest that an inverse fractionation effect occurred (in which the heavy isotope reacts faster than the light isotope) during their oxidation.

Dynamics of communities of bacteria and ammonia-oxidizing microorganisms in response to simazine attenuation in agricultural soil

Autochthonous microbiota plays a crucial role in natural attenuation of s-triazine herbicides in agricultural soil. Soil microcosm study was carried out to investigate the shift in the structures of soil autochthonous microbial communities and the potential degraders associated with natural simazine attenuation. The relative abundance of soil autochthonous degraders and the structures of microbial communities were assessed using quantitative PCR (q-PCR) and terminal restriction fragment length polymorphism (TRFLP), respectively. Phylogenetic composition of bacterial community was also characterized using clone library analysis. Soil autochthonous microbiota could almost completely clean up simazine (100mgkg−1) in 10days after herbicide application, indicating a strong self-remediation potential of agricultural soil. A significant increase in the proportion of s-triazine-degrading atzC gene was found in 6days after simazine amendment. Simazine application could alter the community structures of total bacteria and ammonia-oxidizing archaea (AOA) and bacteria (AOB). AOA were more responsive to simazine application compared to AOB and bacteria. Actinobacteria, Alphaproteobacteria and Gammaproteobacteria were the dominant bacterial groups either at the initial stage after simazine amendment or at the end stage of herbicide biodegradation, but Actinobacteria predominated at the middle stage of biodegradation. Microorganisms from several bacterial genera might be involved in simazine biodegradation. This work could add some new insights on the bioremediation of herbicides contaminated agricultural soils.

Evaluación de rizobacterias promotoras del crecimiento bajo diferentes esquemas de fertilización en el cultivo de maíz variedad HIMECA-95

Bacteria previously isolated, characterized as diazotrophic and inorganic phosphate solubilizers were evaluated under field conditions as plant growth promoters on the maize production when soil fertility was changed. The strains MF1b and MF5, alone and in consortium, were inoculated on maize seeds (HIMECA-95), and these were sown under the following chemical fertility conditions: K, NK, PN, RK, NPK, and NRK (R: phosphate rock). Total dry weight, and N and P contents of the grain were determined at the end of the experiment; also, the % of relative agronomic efficiency (RAE) was calculated. Results showed that inoculation with the strain MF5 alone and in consortium, with the addition of NK fertilizer increased the % RAE in 130 and 403 for the dry weight, in 463 and 116 for the N content, and in 152 and 376 for the P content, respectively, allowing an increase in both production and grain quality. Moreover, it was observed variations among the evaluated parameters which could be related to the low N and P status of the soil, the soil fertility changes after the addition of the highly soluble chemical fertilizers, and the interaction between autochthonous microbial communities and the introduced

Intrinsic potential for immediate biodegradation of toluene in a pristine, energy-limited aquifer

Pristine and energy-limited aquifers are considered to have a low resistance and resilience towards organic pollution. An experiment in an indoor aquifer system revealed an unexpected high intrinsic potential for the attenuation of a short-term toluene contamination. A 30 h pulse of 486 mg of toluene, used as a model contaminant, and deuterated water (D2O) through an initially pristine, oxic, and organic carbon poor sandy aquifer revealed an immediate aerobic toluene degradation potential. Based on contaminant and tracer break-through curves, as well as mass balance analyses and reactive transport modelling, a contaminant removal of 40 % over a transport distance of only 4.2 m in less than one week of travel time was obtained. The mean first-order degradation rate constant was λ = 0.178 day(-1), corresponding to a half-life time constant T1/2 of 3.87 days. Toluene-specific stable carbon isotope analysis independently proved that the contaminant mass removal can be attributed to microbial biodegradation. Since average doubling times of indigenous bacterial communities were in the range of months to years, the aerobic biodegradation potential observed is assumed to be present and active in the pristine, energy-limited groundwater ecosystems at any time. Follow-up experiments and field studies will help to quantify the immediate natural attenuation potential of aquifers for selected priority contaminants and will try to identify the key-degraders within the autochthonous microbial communities.

Fate of carbamazepine and anthracene in soils watered with UV-LED treated wastewaters

Water disinfection technologies based on ultraviolet (UV) radiations emitted by Light-Emitting Diodes (LED), as a wastewater tertiary treatment, have been shown to be promising for water reuse. Here, we assessed the fate of two ubiquitous pollutants, carbamazepine and anthracene, in soil watered with either UV-LED treated wastewaters or irrigation water. After 3 months, anthracene and carbamazepine were transformed two and three times faster respectively, in soils watered with UV-LED wastewater than in soils watered with tap water (probably because of the addition of organic matter by the effluent). Laccase activity was induced in the presence of the pollutants and anthraquinone was found as anthracene product of oxidation by laccases. Moreover, the addition of these pollutants into soil did not affect the functional diversity of autochthonous microbial communities assessed by Ecolog plates. Cellulase, protease and urease activities increased in soils watered with UV-LED treated wastewaters (UV-LED WW), showing transformation of organic matter from the effluent and lipase activity increased by anthracene addition, confirming the potential role of these enzymes as indicators of hydrocarbon contamination.

Biostimulation of the autochthonous microbial community for the depletion of polychlorinated biphenyls (PCBs) in contaminated sediments

In this study, the effect of the biostimulation of the autochthonous microbial community on the depletion of polychlorinated biphenyls (PCBs) in historically contaminated sediments (6.260 ± 9.3 10(-3) μg PCB/ g dry weight) has been observed. Biostimulation consisted of (1) the amendment of an electron donor to favor the dehalogenation of the high-chlorinated PCBs and (2) the vegetation of sediments with Sparganium sp. plants to promote the oxidation of the low-chlorinated PCBs by rhizodegradation. The effects of the treatments have been analyzed in terms of both PCB depletion and changes of the autochthonous bacterial community structure. The relative abundance of selected bacterial groups with reference to untreated sediments has been evaluated by quantitative real-time PCR. The amendment of acetate determined the enrichment of anaerobic dechlorinators like Dehalococcoides sp. Vegetation with Sparganium sp. plants determined the enrichment of either (3) the dechlorinators, Dehalococcoides and the Chloroflexi o-17/DF-1 strains or (4) the Acidobacteria, β-Proteobacteria, Actinobacteria, α-Proteobacteria, Bacteroidetes, and Firmicutes. The combination of the two biostimulation strategy determined the 91.5 % of abatement of the initial PCB content.

Degradation of Gemfibrozil and Naproxen in a river water ecosystem

Pharmaceuticals are nowadays generally recognized to be environmental micropollutants owing to their ubiquitous occurrence in water bodies at concentrations ranging from ng to μg/L. Since they are molecules designed to be biologically active at very low concentrations, their presence is a source of concern for both human and ecosystem health and the ecological effects on receiving ecosystems remain largely unknown.Incomplete removal during biological wastewater treatments is the main source of surface water contamination. Some of the molecules detected are reported to be persistent in surface water while others, although they are not intrinsically persistent (being rapidly degraded), are being continuously introduced into the aquatic ecosystem, so that they can be considered pseudo-persistent compounds. Degradation of a chemical in the aquatic ecosystem depends on a variety of factors, including the compound's properties, environmental factors and above all the presence of a natural microbial community able to degrade it via metabolic and/or co-metabolic pathways.Naproxen, a non-steroidal anti-inflammatory drug and Gemfibrozil, a fibrate drug used as a lipid regulator, have been found in several natural EU and Italian surface waters, including the River Tiber (Rome). In this context, the present work aims to evaluate if the natural bacterial community of the Tiber was able to degrade Naproxen and Gemfibrozil. Moreover the effects of these chemicals on the bacterial community structure in terms of live bacterial abundances and composition were also assessed.For this purpose, different river water microcosms were set up (in the presence/absence of the natural microbial community) and treated with 100μg/L of Naproxen or Gemfibrozil in order to evaluate the disappearance time of 50% of the initial concentrations (DT50).The overall results show that Gemfibrozil (DT50>70days) was more persistent than Naproxen (DT50=27days) and that the autochthonous microbial community had a key role in their degradation. The fact that Naproxen was found in river samples analyzed in a greater concentration was therefore due not to its persistence, but to its pseudo-persistence linked to the spread in its use among the population.