Degradation of organically synthesized herbicides by the symbiosis of plants and endophytes.

simmazine[2-氯-4,6-双（乙胺）-s-三嗪]被广泛用于杂草防治，在日本已被检测到作为污染物存在于地表水和地下水中。许多种微生物已被证明可以降解s-三嗪类除草剂。然而，这些微生物在污染土壤中的大部分施用未能促进除草剂的矿化。这可能是由于接种菌难以在土壤中持续存在并从贫营养环境中获取能量。本文报道了从玉米和大豆中分离的一些内生细菌与寄主植物一起有效地降解辛。前一年以2.6 g m^<-2>的供给量在土壤上种植了茶和甘氨酸。从玉米和大豆的表面灭菌根中分别分离到4株放射农杆菌和6株日本慢生根瘤菌。这些分离株生长在含有0.2 mM simmazine作为唯一氮源的基础液体培养基中。这些菌株培养7天后消耗了50%以上的辛。在土壤中接种可降解西马辛的放射杆菌菌株，导致土壤中西马辛的快速消耗。大豆比玉米对辛碱敏感得多。然而，降解辛马辛的日本芽孢杆菌形成的根瘤增加了大豆对辛马辛的抗性。这些结果表明利用内生菌修复除草剂污染土壤或生产抗西玛辛作物系统的可能性。

Simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] is extensively used for the control of weeds, and has been detected as a pollutant in ground and surface water in Japan. Many kinds of microorganisms have been shown to degrade s-triazine herbicides. A majority of applications of these microorganisms to the contaminated soils, however, failed to promote the mineralization of the herbicides. It seems to be because of the difficulty for the inocula in persisting in soils and obtaining energy sources from the oligotrophic environments. This report presents that some of the endophytic bacteria isolated from com and soybean effectively degrade simazine in association with the host plants.Tea may and Glycine max were grown on the soils which had been supplied with simazine at the rate of 2.6 g m^<-2> in the previous year. Four strains of Agrobacterium radiobacter and six strains of Bradyrhizobium japonicum were isolated from the surface-sterilized roots of com and soybean, respectively. These isolates grew in a basal liquid medium containing 0.2 mM simazine as a sole nitrogen source. More than 50% of simazine were consumed after 7 days of culture of these isolates. Inoculation of the simazine-degrading A. radiobacte strains to coms resulted in the rapid consumption of simazine in the soils. Soybean is much more sensitive to simazine than com. Formation of nodules by the simazine-degrading B. japonicum, however, increased resistance of soybeans against simazine. These results suggest a possibility of utilization of endophytes for remediation of herbicide-contaminated soils or production of simazine resistant cropping systems.