2006 Fiscal Year Final Research Report Summary
Behaviors of Viable but Non-culturable Bacteria in Water Environment and Physiological Response to Chlorine Disinfection
| Project/Area Number |
16560488
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Civil and environmental engineering
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| Research Institution | Hachinohe National College of Technology |
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Principal Investigator |
YAGUCHI Junichi Hachinohe National College of Technology, Department of Civil and Environmental Engineering, Professor, 建設環境工学科, 教授 (80342450)
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| Co-Investigator(Kenkyū-buntansha) |
KANEKO Nakaichiro Hachinohe National College of Technology, Department of Civil and Environmental Engineering, Assistant, 建設環境工学科, 助手 (70099761)
FUKUSHI Kensuke The University of Tokyo, Associate Professor, 環境研究安全センター, 助教授 (30282114)
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| Project Period (FY) |
2004 – 2006
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| Keywords | VNC / fluorescent staining / DAPI / BacLight / chlorine / DVC / CTC / disinfection |
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| Research Abstract |
The objectives of this research are to determine the proportion of physiologically viable bacteria in the water environment and estimate the actual efficacy of disinfection with chlorine using several direct microscopic techniques other than plate counting. 4',6-diamidino-2-phenylindole(DAPI) was used to determine total bacterial numbers, and four fluorescent staining techniques were applied to obtain direct visualization of metabolically active bacteria. 5-cyano-2,3-ditolyl tetrazolium chloride(CTC) was chosen for direct fluorescent microscopic detection of respiring bacteria. BacLight^<TM> kit was used to assess bacterial membrane integrity. Bacteria with growth potential were enumerated using micro-colony technique and direct viable counting(DVC). The total bacterial number in river was 8x10^6〜5x10^9cells/mL, whereas colony forming units on R2A media were 1x10^4〜 4x10^5cells/mL. In the case of wastewater treatment plant, 1〜10% of total bacterial cells could form colonies. The propor
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tion of culturable bacteria in wastewater was significantly higher than that in river. Physiologically active bacteria in river and wastewater treatment plant determined by fluorescent staining were much higher than those obtained by plate counting. BacLight staining technique resulted in the highest viable counts of four fluorescent microscopic methods.
The effect of chlorine on the physiological activity of Escherichia coli was investigated using mixed batch reactors in phosphate buffer (pH 7.2) at 20℃. DAPI total counts were not influenced by an increase in chlorine dosages, while viable counts decreased up to 3 log units with increasing chlorine concentrations. Culturable cells were the most sensitive to chlorine, represented a decline of 6 log units at the residual chlorine concentration of 1.2 mg/L. It was found that direct viable cells were even more chlorine resistant than culturable cells. Applying a simple first-order reaction to the microbial inactivation led to the relationship between the inactivation rates and CT values. The inactivation rate coefficients of direct viable bacteria were one-second to third that of culturable bacteria. Less
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Research Products
(14 results)
