| The coliform group has been used extensively as an indicator of water quality and historically led to the public health protection concept. The quantitative determination of total and fecal coliforms, as indicators of fecal pollution, is essential for quality control of water. Approved traditional methods for the coliform detection include multiple-tube fermentation (MTF), membrane filter (MF), plate count and nephelometry. These methods are complicated in operation and time-consuming. The counting of microbial colony on the plate medium is widely used method, but it is time-consuming and the incubation period is too long (from 24 to 48 h) when remedial measures must be taken.Nanoparticles (1-100 nm) have many effects, such as quantum size effect, surface effect, minisize effect and macroscopic quantum tunnel effect. So they show many distinctive properties and functions. As an essential species among nano materials, nano oxides play an important role in catalysts and sensors. Nano-peroxied has high oxygen overpotential and other merits, so it has been considered as one of the most valuable electrode in environment application.We prepared a nano-peroxide electrode and applied it to determine the population of E. coli by chronoamperometry. And then, we studied on the mechanism of the fast counting. The dissertation includes three sections.Part 1. Preparation of the Ag2O2-PbO2 Modified Electrode and Its Application towards Escherichia coli Fast Counting in WaterIn this paper, we prepared a novel chemically modified electrode and then characterized it with X-ray and AFM. Afterward, this modified electrode was applied to determine the population of E. coli by chronoamperometry. Because the oxidationcurrent of E. coli on the CME is directly proportional to the number of E. coli, the population of E. coli in water can be calculated conveniently. In addition, when we used some other electrodes for this purpose, no response could be found. Our nano crystalline Ag2O2-PbO2 film chemically modified electrode performs higher sensitivity than other single nano material modified electrodes in determination of E. coli. The simplicity and quickness of this method made the modified electrode very attractive for applications.Part 2. Study on Mechanism of E. coli stimulated by nano Ag2O2-PbO2 modified electrodeEscherichia coli is the most thoroughly common gram-negative bacteria which are the dangerous pathogens and can cause human diseases such as traveler's diarrhea, infant diarrhea and infections of the urinary tract. The drug resistance of E. coli is complicated and adventitia of E. coli has great relation to it. The Cell membranes was destructed and permeability was higer after treated by Ag2O2-PbO2 modified electrode. We determined transudatory protein to research the change of permeability of cell membrane. Hypoxanthine, xanthine and uric acid are all the metabolite of nucleotide that take part in most biochemical process. We used liquid chromatography-electrochemical detection to determinate hypoxanthine, xanthine and uric acid in E. coli inoculum after treated by Ag2O2-PbO2 modified electrode. It is showed that how did Ag2O2-PbO2 modified electrode affect metabolism of E. coli.Part 3. Study on Nano Ag2O2-PbO2 Modified Electrode-Induced DNA Damage of E. coliThe fabrication of a novel nano Ag2O2-PbO2 modified electrode is described. Hydroxide radical could be generated on the electrode under an optimized potential. Study on cell membranes' destruction and DNA damage by using this modified electrode to affect E. coli at a certain potential. Content of lipid peroxidate was detected and TEM was used to show destruction of cell membrane of E. coli. DNA damage of E. coli had been studied in detail with electrophoresis and DNA sequencedetermination. The results show that cracking of plasmid DNA and mutation of gene sequence could be induced by nano Ag2O2-PbO2 modified electrode. |
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