A Study of Purple Nonsulfur Bacteria in Activated Sludge Using Moleculr Biotechnology

• Main Authors: Liang_Chih_Min, 梁志銘
• Other Authors: Hung_Chun_Hsiung
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/51466784103581404580

碩士 === 國立中興大學 === 環境工程學系 === 91 === Wastewater phosphorus removal using engineering strategies is one of the important subjects on eutrophication control. In all the available methods, biological phosphorus removal becomes very popular because its low cost, good reliability, and high efficiency. Even though several groups of microorganisms had been isolated from the enhanced biological phosphorus removal (EBPR) process and their ability on accumulating polyphosphate had been confirmed, there is no conclusion on what microorganism plays the major role on the biological phosphorus removal process. From the literatures, more than 80% bacteria in some acetate-feeding phosphorus removal reactors were found to be closely related to Rhodocyclus (belonging to purple non-sulfur phototropic bacteria). Furthermore, the number of these Rhodocyclus - related microorganisms were found to be above 10% in some full-scale wastewater treatment plant. However, the role of purple non-sulfur phototropic bacteria or these Rhodocyclus — related bacteria in the full-scale EBPR process as well as their ability on polyphosphate accumulating is still not clear. The objectives of this study are to understand the possible roles of purple non-sulfur phototropic bacteria or these Rhodocyclus — related bacteria in the full-scale EBPR processes. Traditional isolation and numeration methods for purple non-sulfur bacteria were applied first to compare the difference between sludge samples from normal activated sludge process and EBPR process. After that, molecular methods including fluorescence in situ hybridization (FISH)、polymerase chain reaction (PCR)、agrose gel electrophoresis、denauring gradient gel electrophoresis (DGGE) were used for further bacterial community comparisons. It was shown that the number of purple non-sulfur bacteria is 100 times lower than the previously reported 100,000 cfu/mL. Absorption spectrums of isolated pure cultures showed that more than 90% of purple non-sulfur bacteria isolated were similar to Rhodopseudomonas. Furthermore, numeration result combined with DGGE analysis demonstrated that sludge sample from EBPR process had more purple non-sulfur bacteria (3,000 cells/ml — 6,000 cells/ml) than from normal activated sludge (lower then 1,000 cells/ml). Furthermore, even though normal activated sludge sample had fewer purple non-sulfur bacteria, the composition of these bacteria were more complicated than sample from EBPR process. Isolated purple non-sulfur bacteria were identified by gene extraction and sequencing. Four major species were found in the isolated pure cultures : Rhodopseudomonas palustris、Rhodoplanes elegans、Rhodobacter blasticus and Rhodobacter capsulatus. Among them, Rhodopseudomonas palustris is the most frequently isolated one. One purple sulfur bacteria identified as Allochromatium vinosum was also isolated by the same method used for culturing purple non-sulfur bacteria. However, no pure culture of Rhodocyclus or organisms closely relate to Rhodocyclus were isolated.