ADAPTION OF SUBSURFACE MICROBIAL BIOFILM COMMUNITIES IN RESPONSE TO CHEMICAL STRESSORS
Soil remediation projects rely on the ability of subsurface microbial communities to adapt to varying concentrations of pollutants and to provide effective treatment. The microorganisms have many types of chemical and physical reactions to chemical pollutants that alter their ability to adapt. Two seemingly competitive biological mechanisms, catabolism and the glutathione-gated potassium efflux (GGKE) stress response, were examined to determine the effect they have on the chemical and physical adaptation of subsurface microbial communities during environmental restoration. Catabolism enhances soil remediation efforts by supporting the growth of organisms while degrading the contaminants. The GGKE stress response causes metabolic inactivity, thus preventing any remediation. Lab-scale reactors simulating an aerobic, sandy aquifer were used to support the growth of heterogeneous biofilms that were contaminated with varying concentrations of three environmental pollutants (benzene, pentachlorophenol, and cadmium). Benzene and pentachlorophenol can be catabolized. Cadmium and pentachlorophenol are known to cause the microbial GGKE stress response. Each reactor was contaminated with a varying concentration of one of the chemical stressors over a 30-week period to simulate the onset and washout of a contaminated plume. Changes in the biofilm function and structure were monitored. The occurrence of GGKE was determined by monitoring the bulk liquid potassium concentration with microelectrodes. The biofilm was able to degrade benzene without exhibiting the GGKE mechanism. The biofilm was not able to degrade cadmium, and cadmium did induce the GGKE mechanism. The biofilm was able to degrade up to 20% of the PCP, but a concentration of 10 mg/L did not induce the GGKE mechanism. Soil biofilms will be able to degrade benzene in groundwater contamination quickly. They may not be able to degrade PCP or it will take a much longer time. Cadmium groundwater contamination limits biofilm activity and causes a potassium efflux that may possibly lead to biofilm detachment and washout.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:glutathione gated potassium efflux bioremediation biofilm
Date of Publication:01/01/2003