Showing papers by "Pedro J. J. Alvarez published in 2007"
TL;DR: These findings represent the first demonstrated physiological adaptation response of bacteria to a manufactured nanomaterial, and they show that response inlipid composition and membrane phase behavior depends on both the nC60 concentration and the cell wall morphology.
Abstract: Several fullerene-based nanomaterials generate reactive oxygen species that can damage cells. In this study, we investigated the effect of buckminsterfullerene (C60) introduced as colloidal aggrega...
244 citations
TL;DR: Toxicity was mitigated by adding an antioxidant (glutathione), which suggests that a free radical—induced mechanism or another form of oxidative stress played a role in developmental toxicity.
Abstract: The present paper summarizes, to our knowledge, the first study regarding the developmental toxicity of stable buckminsterfullerene aggregates suspended in water (nC60) using zebrafish (Danio rerio) as a vertebrate model. Zebrafish embryo survival, hatching rate, heartbeat, and pericardial edema were noted and described within 96 h of exposure. Fullerol (a hydroxylated C60 derivative, C60(OH)16-18) at 50 mg/L did not exert toxicity to zebrafish embryos. In contrast, nC60 at 1.5 mg/L delayed zebrafish embryo and larval development, decreased survival and hatching rates, and caused pericardial edema. Toxicity was mitigated by adding an antioxidant (glutathione), which suggests that a free radical-induced mechanism or another form of oxidative stress played a role in developmental toxicity.
207 citations
TL;DR: The production of two reactive oxygen species through UV photosensitization of polyhydroxylated fullerene (fullerol) is shown to enhance viral inactivation rates, suggesting a potential for fullerenes to impact virus populations in both natural and engineered systems ranging from surface waters to disinfection technologies for water and wastewater treatment.
Abstract: The production of two reactive oxygen species through UV photosensitization of polyhydroxylated fullerene (fullerol) is shown to enhance viral inactivation rates. The production of both singlet oxygen and superoxide by fullerol in the presence of UV light is confirmed via two unique methods: electron paramagnetic resonance and reduction of nitro blue tetrazolium. These findings build on previous results both in the area of fullerene photosensitization and in the area of fullerene impact on microfauna. Results showed that the first-order MS2 bacteriophage inactivation rate nearly doubled due to the presence of singlet oxygen and increased by 125% due to singlet oxygen and superoxide as compared to UVA illumination alone. When fullerol and NADH are present in solution, dark inactivation of viruses occurs at nearly the same rate as that produced by UVA illumination without nanoparticles. These results suggest a potential for fullerenes to impact virus populations in both natural and engineered systems rangi...
148 citations
TL;DR: The pilot-scale tank experiment provides the first hydrocarbon and ethanol concentration measurements (and thus, quantification of impacts to groundwater quality) from a subsurface spill of E95 in a well-characterized system with aWell-defined source and the first quantitative near-field-scale evidence that capillarity can significantly retard the vertical dispersion and horizontal advection of ethanol.
54 citations
TL;DR: A 16S rRNA biomarker was developed to estimate the concentration of putative benzene degraders in a methanogenic consortium that has been enriched on benzene for several years and the utility of this primers and probe set to assess anaerobic benzene degradation potential was demonstrated.
Abstract: Summary Benzene is a common groundwater pollutant that is often recalcitrant under the anaerobic conditions that prevail at hydrocarbon-contaminated aquifers. Thus, determining the potential for anaerobic benzene degradation is important to assess the feasibility of intrinsic bioremediation. In this work we developed a 16S rRNA biomarker to estimate the concentration of putative benzene degraders in a methanogenic consortium that has been enriched on benzene for several years. Primers were designed based on phylogenetic information from this consortium. The primers and probe were obtained by sequencing the dominant denaturing gradient gel electrophoresis band of this consortium, which corresponded to Desulfobacterium sp. clone OR-M2. No hybridization was observed with DNA samples from negative controls (i.e. toluene-degrading and dehalorespiring methanogenic consortia that do not degrade benzene). Samples from an anaerobic aquifer column that was bioaugmented with this benzene-degrading consortium showed a strong correlation between benzene degradation activity and the concentration of the target organism. Although our data do not prove that Desulfobacterium sp. is a benzene degrader, its enrichment as a result of benzene consumption and its correlation to anaerobic benzene degradation activity suggest that it either initiates benzene degradation or is a critical (commensal) partner. Therefore, the utility of this primers and probe set to assess anaerobic benzene degradation potential was demonstrated. This is the first report of the use of real-time quantitative PCR for forensic analysis of anaerobic benzene degradation. Whether this biomarker will be adequately selective and broadly applicable to assess benzene degradation potential under
54 citations
TL;DR: Results suggest that indigenous microbial communities are likely to experience population shifts when Z VI-PRBs are installed to exploit several metabolic niches that evolve when ZVI corrodes, whether such population shifts enhance ZVI-PRB performance requires further investigation.
Abstract: Phylogenetic analyses of micro-organisms in groundwater samples from within and around a zero-valent iron (ZVI) permeable reactive barrier (PRB) identified several bacteria that could utilize H2 produced during anaerobic ZVI corrosion and residual guar biopolymer used during PRB installation. Some of these bacteria are likely contributing to the removal of some groundwater constituents (i.e., sulfate). Bacteria concentrations increased from � 10 1 cells mL � 1 at 2 m upgradient to � 10 2 cells mL � 1 within the PRB and � 10 4 cells mL � 1 at 2 to 6 m downgradient. This trend possibly reflects increased substrate availability through the PRB, although a corrosion-induced increase in pH beyond optimum levels within the iron layer (from pH 7 to 9.8) may have limited microbial colonization. Micro-organisms that were detected using quantitative PCR include (iron reducing) Geobacter sp. (putative methanogenic) Archaea, and (sulfate reducing) � -proteobacteria such as Desulfuromonadales sp. Sequencing of DGGE bands also revealed the presence of uncultured dissimilatory metal reducers and Clostridia sp., which was dominant in a sample collected within the ZVI-PRB. These results suggest that indigenous microbial communities are likely to experience population shifts when ZVI-PRBs are installed to exploit several metabolic niches that evolve when ZVI corrodes. Whether such population shifts enhance ZVI-PRB performance requires further investigation.
24 citations
Journal Article•
Abstract: Fe-microorganisms interactions in and around permeable reactive barriers, for reduction of perchloroethylene and hexavalent chromium in polluted aquifers were examined. Biostimulation was done by the addition of a co-substrate for microbial communities already present in the soil. An hydrogen release compound (HRC), a commercial cosubstrate which releases lactic acid at slow rates in presence of water was selected. Results show that HRC addition increases (>100 %) the reduction of PCE in iron-containing systems. Nevertheless, reductive dechlorination was not complete and caused accumulation of toxic metabolites such as trichloroethylene. For chromium reduction, bioestimulation enhanced reduction capability of the systems by 20 %. In this case, the effect was not stimulation of Cr-reducers, but the improvement of redox conditions.
09 Jul 2007