Isolation And Characteristics Of Phosphorus-accumulating Organisms In The Sediments Of Eutrophic Lakes

Under the dual effects of natural factors and human factors, lake eutrophication becomes an increasing crisis in China. Most of large lakes, reservoirs involve the phenomenon of eutrophication. Phosphorus plays a crucial role on the process of eutrophication and so how to reduce the content of phosphorus becomes a key point in the control of eutrophication in lake water body. Phosphate-accumulating Organisms (PAOs) were abundant in the sediment of eutrophic lake and have the ability to transform the soluble phosphorus to its insoluble form. In this regard, it is helpful to investigate the influence of environmental and nutrient factors on the growth and phosphorus-reducing process of PAOs. This paper is expected to offer helpful reference for further study on the elucidation of the mechanism of biological phosphorus removal and the control of lake eutrophication.In this research, eight strains of bacterial were isolated and purified from the collected sediments from different points in those eutrophic lakes, such as Dianchi Lake, MeiLiang and Er'hai Lake. After comparing their ability of phosphorus removal efficiencies, strains of bacteria B and H, which have higher removal efficiencies, were chosen for further research. First, Morphological observation and 16s rDNA identification were performed. The sequence analysis indicated that strains B and H belonged to Arthrobacter and Micrococcus Cohn respectively.Furthermore, the growth characteristics and phosphorus accumulation efficiencies were studied. Specifically, the original content of phosphorus, culture time, oxygen demand, inoculation amount of bacteria, pH value, shaker's rotating speed and temperature, and nutritional factors (carbon and nitrogen sources) were investigated respectively to the growth of bacteria B and H and their effectiveness in phosphorus accumulation.The optimal culture and phosphorus accumulation conditions of these two bacterial were obtained. Strain B has the following optimal condition:culture time 12h, volume of medium 50mL, inoculation amount 2.0%, pH 6-7, rotating speed 120r/min, carbon source was glucose and nitrogen source was peptone; Strain H has the optimal culture condition (culture time 24h, volume of medium 75mL, inoculation amount 2.0%, pH 5-7, rotating speed 120r/min, carbon source was ethanol and nitrogen source was peptone). Strain B was found to grow better and have higher phosphorus accumulation efficiency when cultured on those carbon sources except xylose, ethanol and lactose. Relatively, the requirement of carbon source of Strain B was higher than that of strain H. In general, both of them can grow better and exhibited higher phosphorus accumulation efficiencies on the organic nitrogen source than on the inorganic nitrogen source.