Structural and functional analysis of anaerobic biofilm communities: An integrated molecular and modeling approach
Raskin, Lutgarde
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Permalink
https://hdl.handle.net/2142/19489
Description
Title
Structural and functional analysis of anaerobic biofilm communities: An integrated molecular and modeling approach
Author(s)
Raskin, Lutgarde
Issue Date
1993
Doctoral Committee Chair(s)
Freedman, David L.
Department of Study
Civil and Environmental Engineering
Discipline
Civil Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Microbiology
Engineering, Civil
Engineering, Sanitary and Municipal
Environmental Sciences
Language
eng
Abstract
Eight oligonucleotides, complementary to conserved tracts of 16S ribosomal RNA from phylogenetically-defined groups of methanogens, were designed and characterized for use as hybridization probes for studies in environmental and determinative microbiology. Using these probes, it was determined that Methanosarcina-species, Methanobacteriales, and Methanosaeta-species were the most abundant methanogens present in laboratory acetate-fed chemostats, laboratory municipal solid waste digestors, and full-scale sewage sludge digestors, respectively.
The sensitivity and precision of RNA quantification during nucleic acid hybridization were evaluated by using different nylon membranes and different methods of RNA isolation and denaturation. Magna Charge membranes were found to be superior with respect to sensitivity and precision.
The structure and function of anaerobic microbial communities maintained in laboratory fixed-bed biofilm reactors were tracked for substantial periods of time before and after a major perturbation. This perturbation involved the addition of sulfate to the influent of a reactor which had previously been fed only glucose (reactor MB), while sulfate was withheld from a reactor which had been fed glucose and sulfate (reactor SB). Both reactors contained methanogens and sulfate-reducing bacteria (SRB). Following the addition of sulfate to reactor MB, the process of sulfate reduction started immediately and SRB levels increased; methane production decreased immediately and was later followed by a decrease in the relative concentration of methanogens. Following the changeover to sulfate-free medium in reactor SB, methane production and a substantial increase in the relative levels of methanogens were observed only after approximately 50 days.
A dynamic, relatively structured, biofilm model was developed to simulate the behavior of the reactors after the perturbation described above. For reactor MB, the effluent glucose and sulfate concentrations, as well as the relative concentrations of the different microbial groups were predicted fairly accurately by the model. However, there was a discrepancy between the measured and modeled effluent acetate and methane concentrations. For reactor SB, the same discrepancies were observed. In addition, the model predicted a sharp decrease in the concentrations of the SRB immediately after the change-over as a consequence of an assumption regarding sulfidogenic growth of SRB; in reality, this decrease was much less significant.
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