普施特降解菌Bacillus sp.zx2和zx7生长及降解特性

芽孢杆菌zx2和zx7是普施特高效降解菌,研究其生长和降解特性旨在为普施特污染土壤的生物修复提供科学依据。采用瓶培养法,对芽孢杆菌zx2和zx7的生长特性及单菌和复合菌对普施特的降解特性进行了研究。结果表明,zx2和zx7均可在普施特初始浓度≤200mg·L-1的无机盐培养液中生长良好,zx2在温度25～35℃和pH4.0～7.0时生长良好,而zx7适宜在温度30～35℃和pH5.0～8.0时生长,可见在适应性上二者互补。在最佳条件（温度32℃、pH6.0和普施特初始浓度为200mg·L-1）下,zx2和zx7在无机盐培养液中对普施特降解动态均符合阻滞动力学,半衰期分别为3.8d和2.8d,培养6d时普施特降解率分别为85.81%和90.27%。在培养过程中,zx2的pH是降低的,而zx7的pH基本不变,可初步表明二者降解机理不同;zx2和zx7复合菌（1∶1）对普施特降解率比单菌低,为82.70%,这可能是因为zx2或zx7降解普施特的过程中利用了对方产生的降解产物。

Growth and Degradation Characteristics of Imazethapyr- degrading Bacillus sp. zx2 and zx7

Bacillus sp. zx2 and zx7 are two effective degradation strains for imazethapyr. Study of their growth and degradation characteristics will provide a scientific basis for the practical bioremediation of soil contaminated by imazethapyer, reduce the harmful effect of imazethapyer on environment and human health and contribute to agricultural sustainable development. Bottle culture method was applied to research the growth characteristics of strains zx2, zx7 and their degradation characteristics for imazethapyr with single and mixed strains. The results showed that both of zx2 and zx7 could grow well in inorganic salt medium when the initial concentration of imazethapyr ≤200 mg.L-1. Strain zx2 showed good growth at the condition ：Temperature of 25-35℃ and pH of 4.0-7.0, while the suitable condition for zx7 was temperature of 30-35℃ and pH of 5.0-8.0. Adaptation of the two strains was complementary to each other. Under the optimal growth conditions （temperature 32 ℃, pH 6.0, and initial imazethapyr concentration of 200 mg·L-1）, degradation of imazethapyr by zx2 and zx7 in inorganic salt medium was conformed to the retardation kinetic model. Half-life of imazethapyr degradation was 3.8 days and 2.8 days respectively, and the degradation rates were 85.81% and 90.27% after 6 days culture. In the process of cultivation, pH of zx2 decreased, while pH of zx7 unchanged. It preliminarily showed that the degradation mechanism of zx2 was different from that of zx7. Degradation rate of the mixed strains of zx2 and zx7 was 82.7% which was lower than that of the single strain. It may be due to the reason that zx2 or zx7 utilized the degradation products of each other during their degradating imazethapyr process.