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

西玛津[2-氯-4，6-双（乙氨基）-s-三嗪]广泛用于杂草控制，在日本已被检测为地下水和地表水的污染物。多种微生物对均三嗪类除草剂有降解作用。然而，这些微生物对污染土壤的大多数应用未能促进除草剂的矿化。这可能是由于接种体难以在土壤中持续存在，也难以从贫营养环境中获得能量来源。本文报道了从玉米和大豆中分离到的一些内生细菌能有效地降解西玛津，并与寄主植物联合作用<-2>。从玉米和大豆表面灭菌的根中分别分离到4株辐射农杆菌和6株大豆慢生根瘤菌。这些分离株生长在含有0.2 mM西玛津作为唯一氮源的基础液体培养基中。这些菌株培养7天后，超过50%的西玛津被消耗。西玛津降解菌A.放射性细菌菌株到玉米导致土壤中西玛津的快速消耗。大豆比玉米对西玛津更敏感。西玛津降解菌B形成结核。而大豆根瘤菌则增强了大豆对西玛津的抗性。这些结果表明，利用内生菌修复除草剂污染的土壤或生产西玛津抗性种植系统的可能性。

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.