Darryl Carstensen's MSENV technical report final defense
| December 06, 2005 | |
| Darryl Carstensen presents his MSENV technical report final defense on Wednesday, December 7th at 10:00AM in 2304 McGavran-Greenberg.Culture-independent Identification of Phenol-degrading Bacteria in Activated Sludge by Stable Isotope Probing
(Under the direction of Michael Aitken) Molecular methods in microbiology have provided more detailed insight of the activated sludge process in recent years. However, most of these methods still rely upon culturing of isolates for characterization of the physiology of an organism and extrapolation of those characteristics to more complex systems for the study of environmental samples. Stable isotope probing (SIP) is a method which circumvents the requirement of culturing isolates in order to identify functionally relevant organisms in a system. SIP involves incubating a microbial community with a 13C-labeled carbon source, then recovering 13C-enriched nucleic acids by density-gradient ultracentrifugation. In this study, SIP was applied to a phenol-degrading activated sludge and followed by denaturant gradient gel electrophoresis (DGGE) fingerprinting and construction of 16S rRNA gene clone libraries for identification of phenol degraders by phylogenic analysis. The effects on SIP results of pulse (spike) addition of phenol were compared to those of slow, continuous addition of phenol. Also, the effects of chemostat enrichment of the activated sludge community with phenol as a sole carbon source were examined. Sequences of major phenol-degrading bacteria closely related to two _-proteobacterial sequences previously implicated in phenol-degrading activated sludge were recovered. However, the most abundant sequence associated with phenol degradation was related to organisms in the _-proteobacteria which have not been previously implicated phenol degradation in waste treatment systems. The method of [U-13C]phenol addition in SIP incubations affected the degree of 13C-labeling in the SIP experiment, with the spike-fed samples being more heavily labeled than the continuously fed samples. This finding can have implications for the design and interpretation of future SIP experiments. Committee Members: For further information please contact Rebecca Riggsbee Lloyd by email at Rebecca_Lloyd@unc.edu |
