Effect of Disinfectant on Bacterial Community Structure of Pond Microcosm:A Temperature Gradient Gel Electrophoresis (TGGE) Analysis

Six pond microcosms were constructed to simulate aquatic ecosystems, including one as control. Sodium hypochlorite was added to five experimental microcosms every 24 hours for 13 consecutive days, and then the microcosms were observed for 10 days. The doses of sodium hypochlorite added were 1.0 mg/L, 2.5 mg/L, 5.0 mg/L, 10.0 mg/L and 20.0 mg/L, respectively. Water samples were collected from each microcosm for 8 times during the experiment. All the samples were incubated at 37 ℃ and the total genomic DNA of bacteria was extracted. The 16S rDNA V3 region fragments were amplified from the total DNA and TGGE analysis of 16S rDNA V3 region was conducted. Several major bands from TGGE profiles were recovered from gel, the recoved DNA was reamplified and cloned, and libraries were constructed. Four clones were picked from each library and sent to invitrogen (Shanghai) for sequencing. Sequence analysis was performed to study the polymorphism of TGGE bands and diversity of bacterial community in the microcosms. These results indicated that disinfectant would affect bacterial community structure in environment, but the effects caused by disinfectant in different doses varied markedly. There was a clear dose-effect relationship between disinfectant doses and bacterial community change in the microcosms. The effects of disinfectant at low doses on bacterial community structure were limited and reversible. After microcosm system was gradually adapted to disinfectant, the community structure would be recovered. However, the destructions of disinfectant at high doses to bacterial community structure were severe and irreversible. The community structure would be impossible to recover even if the addition of disinfectant was stopped. All the above suggested that blind and excessive application of disinfectant would destroy microbial ecology in environment severely. Fig 4, Tab 1, Ref 10