For suspended growth activated sludge systems, the growth of bacteria is necessary to avoid washout due to intentional sludge wasting, overflow from secondary clarifiers, and endogenous biomass decay. The central anabolic process, ribosome genesis, is the key to the growth of bacteria, and previous research has described the relationship between cellular ribosome levels and growth rate. Ribosome genesis starts with the expression of rrn operons to produce a polycistronic transcript, which is then processed in two steps by RNases to produce precursor rRNAs and then mature rRNAs. The rRNAs are finally combined with ribosomal proteins to produce a ribosome.
Chloramphenicol is an antibiotic which inhibits the secondary processing of precursor rRNA and leads to abnormally high levels of precursor rRNA. Previously, fluorescence in situ hybridizations (FISH) were used to determine the level of precursor 16S rRNA with unprocessed 3' termini (pre16S-3' rRNA). The results suggested that an unidentified growth inhibitor is present in municipal wastewater that affects a fraction of an Acinetobacter calcoaceticus T microbial population, and this finding formed the basis of my research. The main objective of my research was to determine whether the growth of bacteria in activated sludge systems is inhibited by wastewater.
For this research, two molecular biology methods were utilized to determine whether the secondary processing of precursor 16S rRNA was inhibited. FISH was used to investigate the secondary processing of pre16S-3' rRNA in individual cells, while a novel reverse transcription (RT) method was developed to investigate the secondary processing of the 5' end of precursor 16S rRNA (pre16S-5' rRNA) for an entire population by determining the ratio of pre16S-5' rRNA to 16S rRNA (pre16S-5'/16S). These methods were applied to samples from pure cultures and activated sludge exposed to defined growth media and wastewater. The results of combining these methods with respirometry suggest that a high pre16S-5'/16S is an indication of growth inhibition for A. calcoaceticus T grown in domestic wastewater and the secondary processing of pre16S-5' rRNA is more sensitive than pre16S-3' rRNA. Finally, the RT method was modified to provide a sensitive measure of the growth state of bacterial populations in activated sludge systems.
|School:||University of Cincinnati|
|Department:||Engineering : Environmental Engineering|
|School Location:||United States -- Ohio|
|Source:||DAI-B 79/10(E), Dissertation Abstracts International|
|Keywords:||Bacteria, Confirms, Domestic, Exposed, Inhibition, Novel, Reverse, Transcription, Wastewater|
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