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Nine distinctive bacteria were isolated from a diclofop-methyl-degrading-consortium biofilm and their genomic DNA extracted for genetic characterization. With one exception, all the isolates contained plasmid(s). The consortium degrades diclofopmethyl producing a number of metabolites that are intermediates or substrates for bacteria that degrade chlorinated aromatic compounds. Accordingly, specific catabolic gene PCR primers for chlorinated degradation pathways were designed and tested to determine if these genes are involved in diclofop-methyl degradation. DNA homology analysis between the PCR products and the known catabolic genes investigated by Southern hybridization analysis and by sequencing, suggested that novel catabolic genes are functioning in the isolates. Specific fluorescent oligonucleotides were designed for two of the isolates following the 16S rDNA sequencing and the identification of each of the isolates. These probes were successfully used in whole cell hybridization and will be used in subsequent studies of the microbial ecology of the consortium.

A major cause for dental resin composite restoration replacement is secondary caries attributed to Streptococcus mutans. Salivary esterases were shown to degrade resin composites. Hypothesis: S. mutans contain esterase activities that degrade dental resin composites and adhesives. Esterase activities of S. mutans were measured using synthetic substrates. Standardized specimens of resin composite (Z250), total-etch (Scotchbond-Multipurpose, SB), and self-etch (Easybond, EB) adhesives were incubated with S. mutans UA159 for up to 30 days. Quantification of a bisphenol-glycidyl-dimethacrylate (BisGMA)-derived biodegradation by-product, bishydroxy-propoxy-phenyl-propane (BisHPPP) was performed using high performance liquid chromatography. Results: S. mutans were shown to contain esterase activities in levels comparable to human saliva. A trend of increasing BisHPPP release throughout the incubation period was observed for all materials and was elevated in the presence of bacteria vs. control for EB and Z250 (p<0.05) but not SB. Conclusion: biodegradation by cariogenic bacteria could compromise the resin-dentin interface and reduce the longevity of the restoration.

A major cause for dental resin composite restoration replacement is secondary caries attributed to Streptococcus mutans. Salivary esterases were shown to degrade resin composites. Hypothesis: S. mutans contain esterase activities that degrade dental resin composites and adhesives. Esterase activities of S. mutans were measured using synthetic substrates. Standardized specimens of resin composite (Z250), total-etch (Scotchbond-Multipurpose, SB), and self-etch (Easybond, EB) adhesives were incubated with S. mutans UA159 for up to 30 days. Quantification of a bisphenol-glycidyl-dimethacrylate (BisGMA)-derived biodegradation by-product, bishydroxy-propoxy-phenyl-propane (BisHPPP) was performed using high performance liquid chromatography. Results: S. mutans were shown to contain esterase activities in levels comparable to human saliva. A trend of increasing BisHPPP release throughout the incubation period was observed for all materials and was elevated in the presence of bacteria vs. control for EB and Z250 (p<0.05) but not SB. Conclusion: biodegradation by cariogenic bacteria could compromise the resin-dentin interface and reduce the longevity of the restoration.

Study of a database of 350 giant oilfields show these to be dynamic short lived phenomena, with a median age of 35 Ma. A third show evidence of post-entrapment destructive processes, particularly erosion, fault leakage and gas flushing. Biodegradation is a destructive process most active during oil entrapment. Re-entrapment of oil released from spilling or breached traps is common. These processes are illustrated with case examples from SE Asia and throughout the world. The main controls on oilfield preservation are post-entrapment tectonism and seal type, with temperature and hydrodynamic regimes being secondary factors. Destructive processes are concentrated in shallow and deep zones and in seepage-prone traps such as compressional anticlines. Such factors strongly influence the distribution of preserved light oilfields, with preservation potential maximised in tectonically quiescent basins with evaporite or thick mudstone seals e.g. the Middle East and the Permian Basin, or in basin centres distant from inverted or uplifted zones e.g. Central Sumatra. More attention is required in prospect and regional evaluations to models involving post-entrapment leakage and re-migration.

The impact of different atrazine concentration on a chitinolytic actinomycete and the biodegradation of atrazine by this microbe was examined.Isolates were grown in pure culture in Chitin Mineral Salts Broth with and without addition of atrazine for a two month incubation at room temperature on a rotary shaker. Visual observations, analysis by High Performance Liquid Chromatography (HPLC) and radioisotope methodology were used to determine this impact on chitinolytic activity. Analysis by HPLC and Gas Chromatography with Electron Capture Detector (GC with ECD) were used to determine the breakdown of atrazine.No atrazine derivatives were determined by HPLC and GC analysis. Only the 0.1 ppm atrazine concentration with the actinomycete culture demonstrated tolerance to the atrazine and showed chitinolytic activity in the radioactive assay and chitin derivatives by HPLC. SEM and TEM work determined that the actinomycete was actually a Streptomyces sp. / Department of Biology

Like other aromatic hydrocarbons, benzene is a common soil and groundwater contaminant. It is recognized as a human carcinogen. Exposure of benzene can cause serious negative impacts on human health. Benzene is of major concern due to its toxicity and relatively high water solubility. Benzene is easily biodegraded by ubiquitous bacteria with the presence of free oxygen. However, soil and groundwater contamination with petroleum hydrocarbon often results in the development of anaerobic zones. Bioremediation has been considered as an advantageous alternative in terms of fairly low cost, process flexibility, and on-site utility for the treatment of contaminated soil and groundwater. However, benzene is particularly persistent under anaerobic condition even in the enhanced anaerobic biodegradation process. Although studies have shown that benzene biodegradation could occur under several reducing conditions, the in situ activities of anaerobic benzene degradation are generally low. Bioaugmentation rather than biostimulation may be applicable to accelerate biodegradation process. Successful bioaugmentation requires the inoculation of contaminated soil and groundwater with the strains or consortia of specific degrading capabilities. However, information of dominant species within the microorganisms for anaerobic benzene degradation is still limited. To address this problem, in this study, a benzene-degrading nitrate-reducing culture was established with soil contaminated by gasoline. A nitrate-reducing medium with sulphate, phosphate and other inorganic nutrient was employed to enhance anaerobic benzene degradation. BioSep BioTrap coupled with stable isotope probing and other molecular biological methods were used to identify key anaerobic benzene degraders. Members of genus Dokdonella spp., Pusillimonas spp., and Advenella spp. were found to be the dominant microorganisms during anaerobic benzene degradation, and were hypothesized to be benzene degrader under nitrate-reducing condition.

To ensure oil sands process water (OSPW) is suitable for discharge into the environment, advanced water treatment technologies are required. In this study, integrated ozonation-biodegradation was investigated as a potential treatment option for OSPW. The treatment efficiency was evaluated in terms of naphthenic acid (NA) degradation, chemical oxygen demand (COD), carbonaceous Biological oxygen demand (CBOD), and acute toxicity reduction. Degradation of NAs of more than 99% was achieved using a semi-batch ozonation system at a utilized ozone dose of 80 mg/L combined with subsequent biodegradation. The results also show that ozone decreased the amount of COD while increasing the biodegradability of COD. It was noted that the carbon number and number of NA rings influenced the level of NA oxidation. With a utilized ozone dose of approximately 100 mg/L, the ozonated and biodegraded treated OSPW showed no toxic effect towards bacterium Vibrio fischeri. The results of this study indicate that integrated ozonation-biodegradation is a promising treatment technology for OSPW. / Environmental Engineering

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Kurtis, Kimberly; Committee Member: Kahn, Lawrence; Committee Member: Sobecky, Patricia.