It is nearly always assumed that phosphorus (P) occurs exclusively as phosphate (with an oxidation state of +5) in the environment. Little is known about the redox cycle of P in the environment. However, recent evidence suggested that other less oxidized forms of P (namely reduced P, with an oxidation state lowerthan +5) that were more soluble and active play a critical role in P bioavailability. A bacterial strain (which was named PI) capable of utilizing phosphite (+3) as the sole P source was isolated and screened firstly from sediment of Lake Taihu. It was identified preliminarily as an unknown bacterium according to its physiological-biochemical analysis and the similarity analysis of its 16S rDNA gene sequence. The optimum conditions of pH and temperature for P1 growth were 6.8-7.0 and 30 °C, respectively. The concentrations of 60 mg P/L, 80 mg P/L and 100 mg P/L were set to obtain the optimum phosphite concentration for PI growth. 100 mg P/L phosphite was the optimum P concentration for P1 growth, the rates of the decrease of phosphite and the increase of phosphate in the medium were 11% and 1.6%, respectively. The lower the phosphite concentration, the higher the activity of bacterial alkaline phosphatase (BAP) in the medium. The highest activity of BAP of 1.86 mol PNP/(L·h) was obtained under 60 mg P/L phosphite was added. Phosphite might be changed into the bioavailable P source for Plthrough the oxidation process of BAP. This study just simply found that phosphite can be utilized as a P source by a kind of bacteria. Further research should be carried out to investigate the role of phosphite in the lake P biogeochemical cycle.%从太湖底泥中筛选出一株能够利用亚磷酸盐(+3价)的细菌Pl.通过生理生化实验及16S rDNA基因序列分析鉴定,P1菌与所有已知菌的同源性都很低,属于未知的新菌株.P1菌的最适培养条件为:pH6.5～7.0、温度30℃.Pl菌能以亚磷酸盐为唯一磷源生长,在60～100mg P/L的初始亚磷酸盐培养条件下,100mgP/L的亚磷酸盐培养基中亚磷酸盐减少量最大(1 1％),培养基中生成正磷酸盐的比例最高1.6％.初始亚磷酸盐浓度越低,碱性磷酸酶(BAP)活性越高,60mgP/L的亚磷酸盐培养基中BAP的最高活性为1.86mol PNP/(L菌液·h).P1菌可能通过BAP将亚磷酸盐转化成生物体内所需的磷源.
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