Showing papers by "Daniel B. Oerther published in 2005"

Use of 16S rRNA Gene Terminal Restriction Fragment Analysis To Assess the Impact of Solids Retention Time on the Bacterial Diversity of Activated Sludge

Abstract: Terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA genes was used to investigate the reproducibility and stability in the bacterial community structure of laboratory-scale sequencing batch bioreactors (SBR) and to assess the impact of solids retention time (SRT) on bacterial diversity. Two experiments were performed. In each experiment two sets of replicate SBRs were operated for a periods of three times the SRT. One set was operated at an SRT of 2 days and another set was operated at an SRT of 8 days. Samples for T-RFLP analysis were collected from the two sets of replicate reactors. HhaI, MspI, and RsaI T-RFLP profiles were analyzed using cluster analysis and diversity statistics. Cluster analysis with Ward's method using Jaccard distance and Hellinger distance showed that the bacterial community structure in both sets of reactors from both experimental runs was dynamic and that replicate reactors were clustered together and evolved similarly from startup. Richness (S), evenness (E), the Shannon-Weaver index (H), and the reciprocal of Simpson's index (1/D) were calculated, and the values were compared between the two sets of reactors. Evenness values were higher for reactors operated at an SRT of 2 days. Statistically significant differences in diversity (H and D) between the two sets of reactors were tested using a randomization procedure, and the results showed that reactors from both experimental runs that were operated at an SRT of 2 days had higher diversity (H and D) at the 5% level. T-RFLP analysis with diversity indices proved to be a powerful tool to analyze changes in the bacterial community diversity in response to changes in the operational parameters of activated-sludge systems.

Investigating Student Interest in Post-Secondary STEM Education

Abstract: In a world of rapidly changing technology, knowledge explosion, and globalization, there is a fundamental shift in the type of workforce America needs to remain competitive in a complex and integrated global market. Trends and projections of enrollment and degree production suggest a shortfall in scientific and technical capabilities. For example, from 1993 to 2000, the number of public high school graduates went up by 14.6%, but engineering degree production went down by 6.1%. This decline is particularly disturbing given the changing demographics of the US. American children are falling behind in STEM skills; they are simply not “world-class learners” in science and math. The Third International Mathematics and Science Study tested the students of 41 nations. Children from the U.S. were among the leaders in the fourth grade assessment, but by high school they were almost last 1 . Interest in scientific and mathematical ideas is declining, and students are not being instructed to a level of competence they will need to perform challenging jobs productively.

Paraffin surfaces for culture-based detection of mycobacteria in environmental samples

Abstract: In this paper, we describe the development of paraffin surfaces for culture-based detection of mycobacteria in environmental samples. The surfaces use the well-described paraffinophilic nature of mycobacteria to rapidly and selectively differentiate them from non-target microorganisms. New methods of depositing and patterning paraffin were developed, including using butanol or a heat gun to generate molten paraffin that was subsequently deposited by spin coating and patterned by wet and dry etching techniques. Using these techniques, 18 mm glass wafers with paraffin films of 10–70 µm were fabricated and subsequently etched to form different patterns. Prototype paraffin surfaces were experimentally tested to demonstrate the concept of rapid and selective detection of mycobacteria in environmental samples collected from a municipal sewage treatment plant. Our successful demonstration of the culture-based detection on paraffin substrates presents an alternative approach for tracking microorganisms in complex environmental samples.

Dynamic growth rates of microbial populations in activated sludge systems

Abstract: Results of mathematical modeling and whole cell 16S ribosomal RNA-targeted fluorescence in situ hybridizations challenge the widely held perception that microbial populations in “steady-state” activated sludge systems share a common net growth rate that is proportional to the inverse of the mean cell residence time. Our results are significant because they encourage bioprocess engineers to appreciate the differences in growth physiology among individual microbial populations in complex mixed microbial communities such as suspended growth activated sludge bioreactor systems.