Jump to main content.

Research Project Search
 Enter Search Term:
   
 NCER Advanced Search

2003 Progress Report: Adaptation of Subsurface Microbial Biofilm Communities in Response to Chemical Stressors

EPA Grant Number: R828770C006
Subproject: this is subproject number 006 , established and managed by the Center Director under grant R828770
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: HSRC (2001) - Midwest Hazardous Substance Research Center
Center Director: Banks, M. Katherine
Title: Adaptation of Subsurface Microbial Biofilm Communities in Response to Chemical Stressors
Investigators: Love, Nancy , Stevens, Am
Institution: Virginia Polytechnic Institute and State University , University of Cincinnati
EPA Project Officer: Lasat, Mitch
Project Period: October 1, 2001 through September 30, 2003
Project Period Covered by this Report: October 1, 2002 through September 30, 2003
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (2001)
Research Category: Hazardous Waste/Remediation

Description:

Objective:

The objective of this research project is to determine whether catabolism and microbial stress responses significantly affect how subsurface biofilm communities adapt to dynamic changes in the concentration and type of chemical stressor, and whether the relative contributions of these processes are distinguishable. Effective restoration of contaminated subsurface environments to functioning, healthy ecosystems requires a thorough understanding of how microbiological subsurface communities adapt to the changing concentrations of chemical stressors. We are focusing on a specific stress response, the glutathione-gated potassium efflux (GGKE) system, which is activated in response to electrophilic chemical stressors (see Figure 1). A matrix of environmentally relevant chemical stressors (pentachlorophenol [PCP], cadmium, and benzene) has been selected for this research project so that the relative roles of catabolism versus the GGKE system on biofilm community adaptation during restoration of contaminated sites can be determined.

Approach

Specially designed soil columns were constructed and operated aerobically by exposing the columns to slowly increasing, stable, and then decreasing concentrations of a given contaminant during a 7-month period. The selected contaminants cover a range of properties; two are electrophilic (PCP and Cd), and two are capable of being catabolized (PCP and benzene). Changes in the structure of the soil column microbial communities over space and time will be determined based on biochemical variations and microbial community shifts, and microscopically, using confocal scanning laser microscopy to visualize physical heterogeneities. Changes in function were monitored with microelectrodes targeting key constituents, including dissolved oxygen (DO), oxidation reduction potential (ORP), pH and K+, and by monitoring contaminant fate and bacterial detachment in pore water samples.

Progress Summary:

The column experimental phase of this project took 9 months to complete. During the final phases of the study, perturbation shocks were used to determine both microscale and bulk liquid phase characteristics in response to chemical stress. Soil samples have been stored both at the University of Cincinnati (UC) and at Virginia Polytechnic Institute and State University (VA Tech) for microbial community analysis experiments. The protocols for the community analysis study have been confirmed, and final experiments will commence shortly.

Soil Column Experiments

Columns at UC and VA Tech were put online February 7, 2003, and fed a synthetic mineral salt plus biodegradable feed solution along with one of the following contaminants: PCP, benzene, or cadmium. An unstressed control was maintained in parallel to the other columns (see Figure 1 for a picture and associated schematic for the soil columns). The liquid sampling matrix included contaminant concentration, dissolved organic carbon, potassium, pH, DO, and heterotrophic plate counts. The sand sampling matrix included community profile, proteins, carbohydrates, volatile solids, and heterotrophic plate counts from biofilms. Phase I was comprised of stepwise contaminant concentration increases from 2 to 10 mg/L, Phase II consisted of a constant contaminant loading of 10 mg/L, and Phase III consisted of stepwise concentration decreases from 10 to 3 mg/L contaminant (see Figure 2). At the end of Phase III, spike perturbation experiments were conducted on each column at VA Tech, except the control, and extensively monitored. At UC, spike perturbations were conducted on the mini flow cells and monitored with microelectrodes. As noted earlier, the columns have been disassembled. Prior to this, tracer tests were conducted on each, and a final sample for community analysis was collected from both a set of flow cells and the column.

Data and Results

Brief results are presented in this report. As mentioned previously, the laboratory columns were disassembled, and final data analysis is underway. The student compiling and evaluating the data will be completing her thesis by early January, and a complete report of all results will be submitted at that time. Some results are summarized here from the perturbation experiments that occurred at the end of the experiment, and are the same as the results presented at the 19th Annual International Conference on Soils, Sediments and Water held in Amherst, MA, October 20-23, 2003. The study has yielded the following results:

• Preliminary analysis of the sand column experiment results shows potassium efflux when the perturbating contaminant is seen by the sand column biomass (see Figures 3B and 4B).

• Heterotrophic plate count data show an increase in planktonic bacteria at the beginning of each perturbation (see Figure 3C-Set C and Figure 4C-Sets B and C).

• Benzene perturbation experiment results show potassium uptake and planktonic cell increase during perturbation (data not shown).

Figure 2. Contaminant Concentration Feeding Profile. Red dots reflect times when biomass samples were collected. Perturbation experiments occurred between September 1 and November 5.

Figure 3. (A) Cadmium concentration at each port during perturbation experiment. (B) Normalized potassium concentrations. (C) HPC data showing planktonic bacteria concentration increase in Set B.
Figure 4. (A) PCP concentration at each port during perturbation experiment. (B) Normalized potassium concentrations. (C) HPC data showing planktonic bacteria concentration increase in Set C.
Set A was sampled prior to perturbation, Set B was sampled at beginning of perturbation, Set C was sampled 30 minutes into perturbation, Set D was sampled after perturbation bottle was removed, and Set E was sampled 2 hours after perturbation bottle was removed.

Future Activities:

The protocols for conducting the community analysis work have been tested and confirmed. Those analyses will be initiated on December 1, 2003, and will be completed by January 15, 2004. Those results will be written into a thesis being prepared by Ms. Irina Chakraborty from the University of Helsinki, Finland. At the same time, data analysis from the column studies will be completed and written up in a thesis authored by Ms. Rachelle Rhodes. Ms. Rhodes' thesis will be defended by the end of January. A final report will be compiled and completed shortly afterwards. We anticipate completing a manuscript on the column studies in collaboration with Dr. Paul Bishop and Ms. Denise Gillam this spring. We are hopeful that the community analysis data will yield interesting and important information that also will result in a publication in the spring.

Journal Articles:

No journal articles submitted with this report: View all 4 publications for this subproject

Supplemental Keywords:

pentachlorophenol, PCP, cadmium, benzene, soil, glutathione-gated potassium efflux, GGKE system, fluorescent in situ hybridization, FISH, microelectrodes, confocal laser scanning microscopy, CLSM, microbial biofilm communities, electrophilic chemical stressors, bioavailability, biochemistry, biodegradation, bioremediation of soils, cadmium, cadmium compounds, catabolic biodegradation, contaminants in soil, contaminated sediment, contaminated soil, degradation, genetics, laser scanner microscopy, microbes, microbial biofilm, microbial degradation, phytoremediation. , Toxics, Water, Scientific Discipline, Waste, RFA, Molecular Biology/Genetics, Chemical Engineering, Hazardous Waste, Environmental Engineering, Environmental Microbiology, Environmental Chemistry, Contaminated Sediments, Hazardous, 33/50, Bioremediation, bioavailability, biodegradation, microbial degradation, phytoremediation, laser scanner microscopy, cadmium & cadmium compounds, microbial biofilm, cadmium, contaminated sediment, fluorescent in situ hybridization, PCP, contaminants in soil, contaminated soils, microbiology, contaminated soil, bioremediation of soils, biochemistry, catabolic biodegradation, microbes, toxic chemicals, genetics
Relevant Websites:

http://www.mhsrc.org exit EPA

Progress and Final Reports:
2002 Progress Report
Original Abstract


Main Center Abstract and Reports:
R828770    HSRC (2001) - Midwest Hazardous Substance Research Center

Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R828770C001 Technical Outreach Services for Communities
R828770C002 Technical Outreach Services for Native American Communities
R828770C003 Sustainable Remediation
R828770C004 Incorporating Natural Attenuation Into Design and Management Strategies For Contaminated Sites
R828770C005 Metals Removal by Constructed Wetlands
R828770C006 Adaptation of Subsurface Microbial Biofilm Communities in Response to Chemical Stressors
R828770C007 Dewatering, Remediation, and Evaluation of Dredged Sediments
R828770C008 Interaction of Various Plant Species with Microbial PCB-Degraders in Contaminated Soils
R828770C009 Microbial Indicators of Bioremediation Potential and Success

Top of page

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

Local Navigation

Jump to main content.