微生物降解磺酰脲类除草剂的研究进展

磺酰脲类除草剂是一种高效、广谱、高选择性的除草剂,但其长期广泛使用对生态环境造成了严重破坏,因此对于如何科学合理使用磺酰脲类除草剂、有效防治作物药害和降低对人类的危害等问题成为近年来的研究热点。磺酰脲除草剂在土壤中以化学降解和生物降解方式为主,生物降解是自然界本身具有的一种降解污染物的方式,是一种可行性高、副作用小的方法。近年来,很多学者已经开始研究并利用真菌、细菌等微生物来降解磺酰脲类除草剂,取得了许多重要结果。本文总结了磺酰脲类除草剂的性质、结构以及降解机理、可降解该类除草剂的微生物种类和影响微生物降解效率的因素;最后指出了现阶段存在的问题并对磺酰脲类除草剂的未来发展趋势进行展望。     

三酮类除草剂微生物降解的研究进展

三酮类除草剂是一类高效、广谱、高选择性的除草剂,能够有效地防除玉米地多种阔叶杂草和禾本科杂草。该类除草剂在土壤、水体中残留,易造成地表和地下水污染。有关研究表明,微生物降解有望成为解决该类除草剂残留的有效措施。本文分析了2种三酮类除草剂带来的生态效应,总结了已报道的微生物降解资源,简述了降解基因/酶的研究进展及可能的降解途径,为深入研究三酮类除草剂的生物降解提供一定的信息支撑。     

二硝基苯胺类除草剂微生物降解研究进展

二硝基苯胺类除草剂是一类广谱、高效且广泛使用的除草剂,微生物的降解代谢作用是其在环境中消解的最主要因素。分离筛选除草剂的高效降解菌株、分析其降解途径并阐明其微生物降解机制,可为除草剂残留污染的微生物降解修复提供理论依据和优良的降解菌株、降解基因和酶资源。本文简述了二硝基苯胺类除草剂的微生物降解菌株、降解代谢途径和降解基因/酶的研究进展,为进一步研究该类除草剂的微生物降解及其污染生物修复提供理论依据和资源。     

二苯醚类除草剂的微生物降解研究进展

二苯醚类除草剂是一类广谱、高效、高选择性的除草剂,广泛应用于大豆、花生等农田一年生和多年生阔叶杂草的防除。由于该类除草剂不易降解,多年连续使用会导致其在土壤环境中的大量积累。本文概述了二苯醚类除草剂的基本结构及其对生物的影响,总结了降解二苯醚类除草剂的微生物种类、降解途径和降解过程中关键酶及其基因,分析了影响微生物降解二苯醚类除草剂的因素,对二苯醚类除草剂微生物降解未来的研究方向进行了展望,为深入研究二苯醚类除草剂的生物降解提供参考。     

磺酰脲类除草剂残留的微生物降解研究进展

磺酰脲类除草剂是一类高效、低毒和高选择性的除草剂, 此类除草剂能有效地防除阔叶杂草, 其中有些品种对禾本科杂草也有抑制作用。由于该类除草剂易残留药害及容易对地表水造成污染, 因而其在环境中的持久性和环境安全性备受人们关注。本文综述了磺酰脲类除草剂的应用概况及其作用机理、降解磺酰脲类除草剂的常见微生物种类及影响微生物降解效率的因素, 最后展望了微生物修复技术与抗除草剂的转基因作物是解决除草剂残留药害的最佳途径。     

除草剂对桉树人工林下植物及土壤微生物群落的影响

除草剂在桉树人工林中的应用越来越普遍,但关于除草剂对桉树人工林林下植物和土壤微生物群落的影响知之甚少。通过桉树人工林低剂量高频率（LHF）、中剂量中频率（MMF）、高剂量低频率（HLF）除草剂喷施试验,并与人工除草（MT）为对照,比较分析不同剂量、不同频率除草剂施用对林下植物和土壤微生物群落的影响。结果表明,施用除草剂导致桉树人工林林下植物种类和功能群组成发生显著变化,但并未显著降低林下植物群落物种丰富度和多样性,随除草剂施用频率的降低及恢复时间的增加,物种丰富度及多样性指数呈恢复趋势。除草剂施用也导致土壤养分含量降低。除草剂通过对林下植物群落和土壤养分的负面影响间接影响土壤微生物群落。LHF显著降低藤本植物而显著提高蕨类植物功能群的重要值,从而显著降低了微生物群落、真菌和放线菌的磷脂脂肪酸（PLFA）含量。MMF显著降低木本和藤本植物而显著提高禾草植物功能群的重要值,导致土壤微生物群落和放线菌的PLFA含量显著降低。HLF未显著影响林下植物及土壤微生物群落,但土壤全磷含量显著降低,速效磷含量也大幅下降。施用除草剂显著降低了土壤微生物生物量碳、氮的含量。因此,生产上应减少除草剂的施用,以减少对林下植物和土壤微生物群落的负效应。     

除草剂的微生物降解研究进展

微生物降解是环境中农药消解的重要因素,分离筛选纯培养的农药降解微生物并阐述其降解机制为微生物修复环境的应用提供重要的菌株资源和理论依据。本文简述了广泛使用的8类除草剂(包括有机磷类、磺酰脲类、氯乙酰胺类、均三嗪类、芳氧基苯氧基丙酸酯类、苯氧乙酸类、二硝基苯胺类和硫代氨基甲酸酯类除草剂)的降解微生物资源及其降解途径和降解基因的研究进展,并分析了目前除草剂污染修复存在的问题及未来的发展方向。     

丁草胺对水稻土甲烷释放和厌氧细菌的影响

近年来,我国水稻田的化除面积增加很快,除草剂的使用已成为一种必不可少的手段。因而除草剂大量使用的环境污染问题日益突出,对生态系统的平衡产生威胁性影响,引起农产品农药含量超标,或者即使不超标也由于食物链的生物富集最终进入人体危害健康。除草剂致癌、致突变和致畸胎的事实不胜枚举。除草剂在水稻田使用,至少有70％进入土壤,直接影响土壤微生物的生长和代谢。     

化学除草剂对农田生物群落的影响

从直接作用和间接作用两个方面,在个体、种群和群落3个水平上综述了化学除草剂对农田植物、动物和微生物群落的影响,并提出了今后需要加强研究的几个问题(1)残留在作物和杂草植株内的除草剂及其代谢产物通过食物链和生物富集作用对农田动物群落各级消费者造成的影响;(2)非作物生境使用化学除草剂对毗邻作物生境天敌群落的影响,以及作物生境使用除草剂对邻近非作物生境天敌群落的影响;(3)由除草剂长期使用引起的杂草群落演替、多样性下降、地表覆盖物和地下生物量减少对土壤动物和微生物群落的物种组成、分布、丰富度及其生态功能的影响;(4)化学除草剂与杀虫剂和化肥等其他农用化学品对农田生物群落的联合作用。     

生物除草剂的销售

日本烟草产业(JT)开始实用化本公司第一种微生物农药.它是选择地作用于草坪杂草早熟禾的来自细菌的除草剂.该除草剂是与美国Mycogen公司共同开发的.从1997年5月23日起已由代理店销售.     

Differential effects of the sulfonylurea herbicides chlorsulfuron and sulfometuron methyl on microorganisms

The sulfonylurea herbicides exert their effects on cells via their inhibition of the acetohydroxy acid synthase (AHS) enzymes. Although chlorsulfuron and sulfometuron methyl often affected microbial growth differently their effects on the AHS activities of toluenised cells were similar. Sulfometuron methyl was always a more potent inhibitor than chlorsulfuron. We have postulated that sulfometuron methyl penetrated into microbial cells more readily then did chlorsulfuron. The effect of the herbicides on microbial growth was altered by the composition of the medium and in particular by valine or valine plus isoleucine. Different microorganisms had different complements of AHS isoenzymes which together with differences in permeability were the most likely explanations for the different responses observed. It was pointed out that application of these sulfonylurea herbicides would have significant effects on the microbial ecological balance of soil, and particularly so in alkaline soils. The consequences would be most evident in agricultural situations where the microbial population played an important role in maximising the productivity of crops.     

Effect of phenylurea herbicides on soil microbial communities estimated by analysis of 16S rRNA gene fingerprints and community-level physiological profiles

The effect of three phenyl urea herbicides (diuron, linuron, and chlorotoluron) on soil microbial communities was studied by using soil samples with a 10-year history of treatment. Denaturing gradient gel electrophoresis (DGGE) was used for the analysis of 16S rRNA genes (16S rDNA). The degree of similarity between the 16S rDNA profiles of the communities was quantified by numerically analysing the DGGE band patterns. Similarity dendrograms showed that the microbial community structures of the herbicide-treated and nontreated soils were significantly different. Moreover, the bacterial diversity seemed to decrease in soils treated with urea herbicides, and sequence determination of several DGGE fragments showed that the most affected species in the soils treated with diuron and linuron belonged to an uncultivated bacterial group. As well as the 16S rDNA fingerprints, the substrate utilization patterns of the microbial communities were compared. Principal-component analysis performed on BIOLOG data showed that the functional abilities of the soil microbial communities were altered by the application of the herbicides. In addition, enrichment cultures of the different soils in medium with the urea herbicides as the sole carbon and nitrogen source showed that there was no difference between treated and nontreated soil in the rate of transformation of diuron and chlorotoluron but that there was a strong difference in the case of linuron. In the enrichment cultures with linuron-treated soil, linuron disappeared completely after 1 week whereas no significant transformation was observed in cultures inoculated with nontreated soil even after 4 weeks. In conclusion, this study showed that both the structure and metabolic potential of soil microbial communities were clearly affected by a long-term application of urea herbicides.     

Impact of the ahas transgene and of herbicides associated with the soybean crop on soil microbial communities

Although Brazil has recently reached the position as the second largest producer of genetically modified soybean [Glycine max (L.) Merr.], there are few reports on the effects of transgenic crops and the associated use of specific herbicides on soil microbial communities, both under the edaphoclimatic conditions in Brazil, and in other producer regions in the southern hemisphere. The aim of this study was to evaluate the effects of transgenic soybean containing the ahas gene conferring resistance to herbicides of the imidazolinone group, and of the herbicides associated with transgenic soybeans on the soil microbial community. Twenty field experiments were carried out during three growing seasons (summer of 2006/2007, short-season of 2007 and summer of 2007/2008), in nine municipalities located in six Brazilian states and in the Federal District. The experiments were conducted using a completely randomized block design with four replicates and three treatments: (1) conventional (non-transgenic) soybean cultivar Conquista with conventional herbicides (bentazone + acifluorfen-sodium and other herbicides, depending on the level of infestation in each region); (2) near-isogenic transgenic Cultivance (CV127) containing the ahas gene, with conventional herbicides; (3) transgenic Cultivance with specific herbicide of the imidazolinone group (imazapyr). As the objective of the study was to verify impacts of the transgene and herbicides on the soil microbial community of the whole area and not only a punctual rhizospheric effects, samples were taken at the 0–10 cm layer prior to cropping and at R2 soybean growth stage, between plant rows. Quantitative (microbial biomass C and N, MB-C and MB-N) and qualitative (DGGE of the 16S rDNA region) parameters of soil microbial community were evaluated. No qualitative or quantitative differences were found that could be attributed to the transgene ahas. A comparison of Cultivance soybean with conventional and imidazolinone-group herbicides applications also failed to reveal differences that could be attributed to the specific use of imazapyr, even after three consecutive croppings at the same site. Finally, no differences were detected between conventional (Conquista and conventional herbicides) and transgenic soybean managements (Cultivance and imazapyr). However, marked differences were observed in MB-C and MB-N between the different sites and times of year and, for the 16S rDNA-DGGE profiles, between different sites. In conclusion, microbial community evaluations were found to be sensitive and viable for monitoring different technologies and agricultural management methods, but no differences could be attributed to the ahas transgene for three consecutive cropping seasons.     

Positive plant microbial interactions

Problems and concerns in relation to the use of inorganic fertilisers, irrigation, herbicides and pesticides have led to the search for alternative strategies to combat limiting soil nutrient and water levels and the effect of weeds and pests on crops. Greater utilisation of microorganisms in agricultural systems could possibly allow reductions in the use of inorganic fertilisers, water, herbicides and pesticides with no impact on crop yield. Positive plant microbial interactions which are currently under study are considered here.     

Effect of foliar application of herbicides,Benthiocarb, 2,4-D and Fluchloralin on phyllosphere microflora of potato

Three herbicides, Benthiocarb, 2,4-D and Fluchloralin were evaluated for their effect on leaf surface microflora of potato. In general, the application of herbicides resulted into a drop in the microbial population. Throughout the study herbicide treated leaves harboured less population compared to the untreated ones.     

Impact of an Herbicide Combination of Bromoxynil and Prosulfuron on Soil Microorganisms

Soil microcosm experiments were used to investigate the effects on growth and activity of soil microorganisms of an herbicide combination (60% bromoxynil + 3% prosulfuron) frequently used to provide a broad spectrum control of weed species. Culturable aerobic bacteria, fungi, and actinomycetes, the fundamental groups of heterotrophic microorganisms, and nitrifiers, considered a very sensitive group to these compounds, were evaluated. Since herbicides have been found to inhibit decomposition of cellulose in soil, the effects on cellulolytic bacteria and fungi were determined. Dehydrogenase activity as a measure of microbial activity was another parameter considered. The results emphasized a tendency of reversible stimulatory/inhibitory effects of the tested compounds on soil microorganisms, with fungi as an exception. A long-lasting negative action on the activity of the dehydrogenase (DHA), commonly used as an index of the overall microbial activity in soil, was found. The magnitude of these effects were dependent on the assayed concentrations of the herbicides mixture. We concluded that the presence of bromoxynil + prosulfuron could induce significant changes in the microbial populations of the soil, concerning the activity and balance of microbial community. Possible environmental risks must be considered. Dehydrogenase activity was shown to be an important indicator of side-effects attributed to these herbicides.