Showing papers by "Daniel B. Oerther published in 2004"

Bacterial Competition in Activated Sludge: Theoretical Analysis of Varying Solids Retention Times on Diversity

Abstract: A mechanistic model for activated sludge sewage treatment was developed to predict exploitative competition of six aerobic heterotrophic bacterial species competing for three essential resources. The central hypothesis of the model is that in a multispecies/limiting resource system the number of coexisting bacterial species, N, exceeds the number of limiting resources, K, available for them. The explanation for this is that for certain species combinations, the dynamics of the competition process generate oscillations in the abundances of species, and these oscillations allow the coexistence of greater number of species than the number of limiting resources (N > K). This result is a direct contradiction of an existing activated sludge steady state competition theory, “the principle of competitive exclusion,” which states that the competition process proceeds to equilibrium, allowing only N ≤ K species to coexist. The model was used to investigate the effect of varying solids retention times on the diversity of species using the conventional, completely mixed activated sludge configuration. The results of model simulations showed that for a certain range of solids retention times (2.28–5.66 days) the competition of six species for three essential resources produces oscillations within the structure of the bacterial community allowing for the sustained growth of more than three species on three resources.

Developing rapid detection of mycobacteria using microwaves

Abstract: In this paper, we describe the development of a culture-based biochip device for rapid detection of mycobacteria in environmental samples Individual biochips rely upon the unique paraffinophilic nature of mycobacteria to rapidly and selectively adhere to the surface of the device We used prototype biochips to experimentally demonstrate the concept of rapid and selective detection of mycobacteria by testing pure cultures and using epifluorescence microscopy to visualize microorganisms on the surface As an alternative, rapid approach for identifying the biomass on the biochip surface, we used microwaves in the 10 to 26 GHz frequency range The results of this study indicate that different microorganisms are responsible for specific shifts in resonance frequencies of a microwave cavity By combing the semi-selective paraffin surface of the biochip with the microorganism-specific response to the microwaves, we have developed an improved analytical system with the potential to rapidly identify and enumerate mycobacteria in environmental samples in as little as 2 h

Culture-Based Biochip for Environmental Monitoring

Abstract: In this paper, we describe the development of a culture-based biochip for detecting mycobacteria in environmental samples. The biochips use the paraffinophilic nature of mycobacteria to rapidly detect and differentiate them from non-target micro-organisms. New methods of depositing and patterning paraffin were developed to fabricate prototype biochips. Biochips were experimentally tested to demonstrate rapid detection of mycobacteria in environmental samples collected from a municipal sewage treatment plant. Our successful demonstration of the culture-based biochip technology presents an alternative approach for developing new technology to track microorganisms in complex environmental samples.