May 05, 2006
Sabrina Powell presents her Doctoral Dissertation Defense on Monday, May 8th at 9:30am in 2301 McGavran-Greenberg. Full details follow.Stable Isotope Probing of Salicylate-Degrading Bacteria in Polycyclic Aromatic Hydrocarbon-Contaminated Soil

Polycyclic aromatic hydrocarbons (PAHs) are widespread soil and sediment pollutants, and the carcinogenic nature of some PAHs has led to increased concern over their potential effects on human health and the environment. Salicylate is an inducer of polycyclic aromatic hydrocarbon (PAH) metabolism in many bacteria, and its addition to contaminated soil or sediment has been proposed as a means of stimulating PAH degradation during bioremediation. Stable-isotope probing (SIP), a technique which uses 13C-labeled growth substrates to link microbial function with identity via selective recovery of “heavy” 13C-labeled DNA, was used to identify degraders of salicylate, naphthalene, and phenanthrene in an aerobic slurry-phase bioreactor treating PAH-contaminated soil. Salicylate- and naphthalene-degraders were similar to each other but not to phenanthrene degraders. SIP was also used to identify organisms enriched for by alternative methods of salicylate addition: spike (all at once) or continuous (slow addition throughout the incubation). Spike and continuous salicylate addition were found to select for differing populations of salicylate utilizers. Real-time quantitative PCR primers were designed to quantify the abundances of organisms selected for by each salicylate addition method. To evaluate salicylate as a stimulant of PAH degradation, the effect of spike or continuous salicylate addition on initial mineralization rates of naphthalene, phenanthrene, and benzo[a]pyrene was measured. Spike addition of salicylate was found to increase the mineralization of naphthalene by 50% relative to the unenriched control. The combined results of this study suggest that (1) the method of substrate addition affects the outcome of SIP incubations, and (2) salicylate has the potential to stimulate naphthalene removal in contaminated systems.

Committee members:

Mike Aitken
Fred Pfaender
Steve Whalen
Bob Bourret
Mike Hyman

For further information please contact Rebecca Riggsbee Lloyd by email at Rebecca_Lloyd@unc.edu

 

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