Progress 07/01/05 to 09/30/09
Outputs
OUTPUTS: Activities: This is the termination report for Hatch Project "Microbial Dynamics of Biodegradation and Transport of Contaminants in Soil". The overall goal of the proposed project was to enhance our understanding of the effect of soil and microbial heterogeneities on the in-situ dynamics of contaminant biodegradation activity. There were two focal areas for this project. The first involved examination of the application of biosurfactants to enhance biodegradation of organic contaminants in soil. Sorption of rhamnolipid biosurfactants to various soil constituents was studied to help predict amounts of rhamnolipid that would be needed for remediation applications based on soil properties. The second focal area involved characterization of the distribution and activity of the microbial populations responsible for biodegradation. This research focused on an actual chlorinated solvent-contaminated field site in Tucson, Arizona and illustrated the use of an integrated, multiple-method approach for assessing natural attenuation at a complex chlorinated solvent-contaminated site. Products: This research was used to help develop informational materials on chlorinated solvents including two Sci-Transfer bulletins targeted to professionals and remedial project managers "Chlorinated Solvent Contaminants in Arizona Aquifers, Parts I and II (Part I: Sources, Properties, Health Effects and Fate, Part II: Innovative Remediaiton Methods and Site Characterization Strategies). Further, an information sheet "What is TCE" was developed for the general public. These materials can be found on the webpage: http://superfund.pharmacy.arizona.edu/prof_comm_info.php PARTICIPANTS: Raina Maier, PhD, is the project PI and guides the direction of the research work in collaboration with the co-PI. The is an interdisciplinary project and Dr. Maier brings expertise in environmental microbiology to the questions being asked. Mark Brusseau, PhD, is the project co-PI and co-directs the research work. Dr. Brusseau brings expertise in environmental chemistry and hydrology that is complementary to the environmental microbiology discipline represented by Dr. Maier. This project has provided opportunities for professional development for several PhD students including Francisco Ochoa-Loza (working with Maier) and Concepcion Carreon-Diazconti (working with Brusseau). Both students have gone on take positions in Mexico : Ochoa-Loza with SEMARNAT (the Mexican equivalent of EPA) and Carreon-Diazconti with Universidad Autonoma de Baja California. TARGET AUDIENCES: The target audiences for this research include a scientific audience for whom we have provided knowledge through publishing the results of research outcomes for this project as well as professionals and remedial project managers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The research from this project has had several major impacts. First, the data generated from the biosurfactant studies were used to obtain a major NSF Collaborative Research in Chemistry grant. This was possible in part because this project helped provide evidence of the unique surface and interfacial properties of rhamnolipids. This major award was made to study these properties and obtain an understanding of how to make these materials more relevant to bioremediation specifically and biotechnology more generally. The data generated from the chlorinated solvent field study have been used to help inform site owners and remedial project managers about behavior of chlorinated solvents in field sites. This information has been useful across a wide range of stakeholders including the general public through participation in Community Advisory Board meetings and production of information materials, remedial project managers through publication of information materials, and scientists through peer-reviewed publications.
Publications
- Neilson, J.W., L. Zhang, T.A. Veres, K.B. Chandler, C.H. Neilson, J.D. Crispin, J.E. Pemberton, and R.M. Maier. 2010. Heavy metal effects on transcriptional expression of rhlB/rhlC genes and dirhamnolipid/monorhamnolipid ratios. Appl. Microbiol. Biotechnol., in review.
|
Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Biodegradation is one of the major processes influencing the transport and fate of organic contaminants in subsurface systems. An understanding of biodegradation properties is critical for determining contamination potential and the feasibility for remediation. We have continued our focus on two aspects of understanding biodegradation. One aspect is to gain a better understanding of biosurfactants, specifically rhamnolipids, and their role in enhancing the biodegradation of slightly soluble compounds in soil systems. Biosurfactants impact not only the solubility of contaminants but also can profoundly modify soil surface properties and thus the interaction between soil and contaminants. Biosurfactants are made in complex mixtures that can exceed 40 congeners and each congener has its own unique properties. In order to explore whether there are environmental controls on congener production we have examined the impact of metals on the relative production of monorhamnolipid and dirhamnolipid the major types of rhamnolipids produced. Our work has focused on the control of the biosynthetic genes for rhamnolipid production. Specifically, we have examined the effect of metals on transcriptional regulation of the rhlB and rhlC genes that control the production of monorhamonlipid (rhlB) and dirhamnolipid (rhlC). Most isolates that produce rhamnolipid make a mixture of these two surfactants but their chemical and surface properties are quite different. The second area we have worked in involves characterization of the distribution and activity of the microbial populations responsible for biodegradation. This is especially true for evaluating biodegradation at the field scale, where it is well known that both contaminant distribution in the subsurface and the subsurface itself are heterogeneous and that this heterogeneity, may exert significant impacts on system properties ranging from water flow to solute transport to microbial distribution, and, thus, on contaminant bioavailability. This research has focused on a chlorinated-solvent contaminated field site in Tucson, Arizona. Isotopic analysis and molecular-based bioassay methods were used in conjunction with geochemical data to assess the intrinsic reductive dechlorination potential in this site. Groundwater samples were obtained from monitoring wells within a contaminant plume that contains tetrachloroethene and its metabolites trichloroethene, cis-1,2-dichloroethene, vinyl chloride, and ethene, as well as compounds associated with free-phase diesel present at the site. Compound specific isotope (CSI) analysis was performed to characterize biotransformation processes influencing the transport and fate of the chlorinated contaminants. DNA-PCR analysis was used to assess the presence of indigenous reductive dechlorinators. The target regions employed were the 16s rDNA sequences of Dehalococcoides sp. and Desulfuromonas sp., and DNA sequences of genes pceA, tceA, bvcA, and vcrA, which are encoded by reductive dehalogenase enzymes. PARTICIPANTS: Raina Maier, PhD, is the project PI and guides the direction of the research work in collaboration with the co-PI. The is an interdisciplinary project and Dr. Maier brings expertise in environmental microbiology to the questions being asked. Mark Brusseau, PhD, is the project co-PI and co-directs the research work. Dr. Brusseau brings expertise in environmental chemistry and hydrology that is complementary to the environmental microbiology discipline represented by Dr. Maier. This project has provided opportunities for professional development for several PhD students including Francisco Ochoa-Loza (working with Maier) and Concepcion Carreon-Diazconti (working with Brusseau). Both students have gone on take positions in Mexico : Ochoa-Loza with SEMARNAT (the Mexican equivalent of EPA) and Carreon-Diazconti with Universidad Autonoma de Baja California. TARGET AUDIENCES: The target audience for this research is primarily a scientific audience for whom we have provided knowledge through publishing the results of research outcomes for this project. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Results from biosurfactant studies show that while metals such as cadmium, copper, and zinc do not impact bacterial growth or the amount of rhamnolipid produced, they do significantly increase the relative amounts of dirhamnolipid produced. Dirhamnolipids are chemically different from monorhamnolipids; they have higher solubility and interact with both contaminants and degrading cells differently. The fact that the chemical environment surrounding a cell can influence the type of rhamnolipid produced has implications not only for remediation purposes but also for production of these materials as fine chemicals. A manuscript is in preparation describing this work. Results from the chlorinated-solvent contaminated field site indicate that relevant chlorinated solvent-degrading microbial populations are present and that reductive dechlorination is presently occurring at the site. The results further show that potential degrader populations as well as biotransformation activity is non-uniformly distributed within the site. The compound specific isotope analysis provided a conservative estimate of 14 to 20% for the average extent of dichloroethene biodegradation, which has become the major chlorinated contaminant within the plume. The results of laboratory microcosm studies conducted using microorganisms collected from the field site confirmed the reductive dechlorination of tetrachloroethene. This study illustrates the benefits associated with employing an integrated, multiple-method approach to the assessment of natural attenuation for chlorinated-solvent contaminated sites. Isotopic analyses for complex field sites such as the focus of this study are influenced by uncertainty to a significantly greater extent than typical laboratory studies. Potential sources of uncertainty include the presence of organic liquid, spatial variability, and simultaneous production and consumption of multiple compounds. To partly address this uncertainty, a second isotopic data set was collected from the same location more than two years after the first. Comparing the two data sets, it is evident that DCE has become further enriched in 13C while the aqueous concentrations have declined. The results obtained for the two sampling rounds are very consistent, supporting the robustness of the CSI analysis.
Publications
- Carreon-Diazconti, C., J. Santamaria, J. Berkompas, J.A. Field, M.L. Brusseau. 2009. Assessment of In-situ Reductive Dechlorination Using Functional Gene PCR, Compound-specific Stable Isotopes, and Geochemical Data. Environ. Sci Technol. (in press). DOI: 10.1021/es8020827.
|
Progress 01/01/07 to 12/31/07
Outputs
Biodegradation is one of the major processes influencing the transport and fate of organic contaminants in subsurface systems. An understanding of biodegradation properties is critical for determining contamination potential and the feasibility for remediation. We have worked on two aspects of understanding biodegradation during the past year. First, we have worked on characterization of the sorption behavior of bacterially produced surfactants (biosurfactants) to better understand their role in enhancing the biodegradation process in soil systems. It is well-known that these molecules enhance the ability of bacteria to sequester and degrade hydrophobic contaminants. The second area we have worked in involves characterization of the distribution and activity of the microbial populations responsible for biodegradation. This is especially true for evaluating biodegradation at the field scale, where it is well known that both contaminant distribution in the subsurface and
the subsurface itself are heterogeneous and that this heterogeneity, may exert significant impacts on system properties ranging from water flow to solute transport to microbial distribution, and, thus, on contaminant bioavailability. This research has focused on a chlorinated-solvent contaminated field site in Tucson, Arizona. Isotopic analysis and molecular-based bioassay methods were used in conjunction with geochemical data to assess the intrinsic reductive dechlorination potential in this site. Groundwater samples were obtained from monitoring wells within a contaminant plume that contains tetrachloroethene and its metabolites trichloroethene, cis-1,2-dichloroethene, vinyl chloride, and ethene, as well as compounds associated with free-phase diesel present at the site. Compound specific isotope analysis was performed to characterize biotransformation processes influencing the transport and fate of the chlorinated contaminants. DNA-PCR analysis was used to assess the presence of
indigenous reductive dechlorinators. The target regions employed were the 16s rDNA sequences of Dehalococcoides sp. and Desulfuromonas sp., and DNA sequences of genes pceA, tceA, bvcA, and vcrA, which are encoded by reductive dehalogenase enzymes.
Impacts
Results from biosurfactant studies have described the effect of different soil constituents on the sorption of a rhamnolipid biosurfactant. Results showed that monorhamnolipid (R1) sorption is concentration dependent. At low R1 concentrations that are relevant for enhancing organic contaminant biodegradation, R1 sorption followed the order: hematite > kaolinite > MnO2 = illite = Ca-montmorillonite > gibbsite > humic acid-coated silica. At high R1 concentrations, relevant for use in complexation/removal of metals or organics, R1 sorption followed the order: illite >> humic acid-coated silica > Ca-montmorillonite > hematite > MnO2 > gibbsite = kaolinite. These results allowed prediction of R1 sorption by a series of six soils. Further, a comparison of R1 and R2 (dirhamnolipid) showed that the R1 form sorbs more strongly alone than when in a mixture of both the R1 and R2 forms. This information can be used to estimate, on an individual soil basis, the extent of
rhamnolipid sorption. This is important for determining: (1) whether rhamnolipid addition is a feasible remediation option and (2) the amount of rhamnolipid required to efficiently remove the contaminant. Results from the chlorinated-solvent contaminated field site indicate that relevant chlorinated solvent-degrading microbial populations are present and that reductive dechlorination is presently occurring at the site. The results further show that potential degrader populations as well as biotransformation activity is non-uniformly distributed within the site. The compound specific isotope analysis provided a conservative estimate of 14 to 20% for the average extent of dichloroethene biodegradation, which has become the major chlorinated contaminant within the plume. The results of laboratory microcosm studies conducted using microorganisms collected from the field site confirmed the reductive dechlorination of tetrachloroethene. This study illustrates the benefits associated with
employing an integrated, multiple-method approach to the assessment of natural attenuation for chlorinated-solvent contaminated sites. A manuscript describing this work is in preparation.
Publications
- Lebron-Paler, A., J.E. Pemberton, W.C. Otto, B.K. Becker, C.K. Larive and R.M. Maier. 2006. Determination of the acid dissociation constant of the biosurfactants monorhamnolipid in aqueous solution by potentiometric and spectroscopic methods. Anal. Chem. 78:7649-7658.
- Ochoa-Loza, F.J., W.H. Noordman, D.B. Jannsen, M.L. Brusseau, and R.M. Maier. 2007. Effect of clays, metal oxides, and organic matter on rhamnolipid biosurfactant sorption by soil. Chemosphere, 66:1634-1642.
|
Progress 01/01/05 to 12/31/05
Outputs
Biodegradation is one of the major processes influencing the transport and fate of organic contaminants in subsurface systems. An understanding of biodegradation properties is critical for determining contamination potential and the feasibility for remediation. The standard approach for characterizing biodegradation has been to conduct batch dissipation studies. While this method has provided useful information, it is limited by several constraints. For example, several investigators have shown that biodegradation rates measured in static batch experiments differ from those measured under dynamic flow and transport conditions, the latter being more representative of actual field systems. Furthermore, there has been little focus on characterizing the microbial dynamics inherent to biodegradation processes occurring under transport conditions. Clearly, an accurate characterization of contaminant biodegradation would require an understanding of the distribution and
activity of the microbial populations responsible for biodegradation. This is especially true for evaluating biodegradation at the field scale, where it is well known that both contaminant distribution in the subsurface and the subsurface itself are heterogeneous and that this heterogeneity, may exert significant impacts on system properties ranging from water flow to solute transport to microbial distribution, and, thus, on contaminant bioavailability. Thus, the goal of the proposed project is to enhance our understanding of the effect of soil, contaminant, and microbial heterogeneities on the in-situ dynamics of contaminant biodegradation activity. The results of the proposed research will enhance our understanding of how coupled physical and microbial processes influence the transport and fate of contaminants in soil. In the past year, we have investigated the influence of microbial variability on contaminant transport behavior showing that variability inherent to natural microbial
systems can cause variability in transport behavior even under controlled laboratory conditions and concomitantly enhance the uncertainty of biokinetic parameters obtained from laboratory studies. We have also examined the impact of a nonaqueous phase liquid (NAPL) on biodegradation of a model contaminant, phenanthrene. Results show that partitioning of phenanthrene into the NAPL phase limits bioavailability at high NAPL mass. Further experiments showed that the presence of NAPL resulted in a lower cell yield (less cell growth) during phenanthrene biodegradation due to NAPL-induced changes in phenanthrene metabolism.
Impacts
Results from this project will provide information useful for predicting transport and fate, for evaluating groundwater contamination potential, and for the manipulation of contaminated subsurface systems to enhance the effectiveness of remediation techniques. Such information would clearly have significance for maintaining the long-range sustainability of soil and subsurface environments in the US.
Publications
- Brusseau, M.L., S.K. Sandrin, L. Li, I. Yolcubal, F.L. Jordan, and R.M. Maier. 2006. Biodegradation during contaminant transport in porous media: the influence of microbial system variability on transport behavior and parameter determination. Water Res. Res. 42:
- Sandrin, T.R., W.B. Kight, W.J. Maier, and R.M. Maier. 2006. Influence of a nonaqueous phase liquid (NAPL) on biodegradation of phenanthrene. Biodegrad., DOI: 10.1007/s10532-005-9013-y.
|
|