土壤: 微生物的最后栖息地?

The question is asked whether soils can be regarded as extreme environments with respect to microorganisms. After defining some extreme environments in a general sense, special properties of extreme environments are compared to soil habitats, with special emphasis laid on time frame and localities. In relation to water availability, nutrients and other properties, such places as aggregates can show properties of extreme habitats. These features, which can act at different levels of the system from the community level down to the cellular level, are summarized as stress factors. The latter, where many switches are located leading to different strategies of survival, is described as the most important one. This raises the question of how organisms have adapted to such conditions. The soil system demands a broad spectrum of adaptations and/or adjustments for a highly variable environment. The soil microorganisms' adaptation can thus be seen as the highest kind of flexibility and is more useful than any other special adaptation.     

Cell-Associated Adsorption of Thorium or Uranium from Aqueous System Using Various Microorganisms

The cell-associated adsorption of thorium or uranium from the solution containing each metal only at pH 3.50 using various microorganisms was examined. Among the species tested, high thorium adsorption abilities were exhibited by strains of the gram-positive bacteria Arthrobacter nicotianae IAM12342, Bacillus megaterium IAM1166, B. Subtilis IAM1026, Micrococcus luteus IAM1056, Rhodococcus erythropolis IAM1399, and Streptomyces levoris HUT6156. And high uranium adsorption abilities were found in some gram-positive bacterial strains S. albus HUT6047, S. levoris HUT6156, and A. nicotianae IAM12342. Among these highly efficient thorium and uranium adsorbing microorganisms, S. levoris, which could adsorb the largest amount of uranium from the aqueous solution at pH 3.50, could adsorb about 383 mol thorium and 390 mol uranium per gram dry weight of microbial cells from the solution containing thorium or uranium at pH 3.50. The amount and time course of thorium adsorbed were almost unaffected by co-existing uranium; however, the adsorption of thorium was faster when carried out after the adsorption of uranium. Thorium adsorption also became faster when uranium was added after thorium adsorption. The effect of pH on thorium adsorption was also discussed.     

Long‐term effects of fertilization on some soil properties under rainfed soybean‐wheat cropping in the Indian Himalayas

This study aims to examine the effects of long‐term fertilization and cropping on some chemical and microbiological properties of the soil in a 32 y old long‐term fertility experiment at Almora (Himalayan region, India) under rainfed soybean‐wheat rotation. Continuous annual application of recommended doses of chemical fertilizer and 10 Mg ha^–1 FYM on fresh‐weight basis (NPK + FYM) to soybean (Glycine max L.) sustained not only higher productivity of soybean and residual wheat (Triticum aestivum L.) crop, but also resulted in build‐up of total soil organic C (SOC), total soil N, P, and K. Concentration of SOC increased by 40% and 70% in the NPK + FYM–treated plots as compared to NPK (43.1 Mg C ha^–1) and unfertilized control plots (35.5 Mg C ha^–1), respectively. Average annual contribution of C input from soybean was 29% and that from wheat was 24% of the harvestable aboveground biomass yield. Annual gross C input and annual rate of total SOC enrichment from initial soil in the 0–15 cm layer were 4362 and 333 kg C ha^–1, respectively, for the plots under NPK + FYM. It was observed that the soils under the unfertilized control, NK and N + FYM treatments, suffered a net annual loss of 5.1, 5.2, and 15.8 kg P ha^–1, respectively, whereas the soils under NP, NPK, and NPK + FYM had net annual gains of 25.3, 18.8, and 16.4 kg P ha^–1, respectively. There was net negative K balance in all the treatments ranging from 6.9 kg ha^–1 y^–1 in NK to 82.4 kg ha^–1 y^–1 in N + FYM–treated plots. The application of NPK + FYM also recorded the highest levels of soil microbial‐biomass C, soil microbial‐biomass N, populations of viable and culturable soil microbes.     

土壤微生物生态学在农业中的应用研究综述

土壤微生物生态学是陆地生态系统研究中最重要的组成部分,是土壤学、微生物学和生态学相互渗透、相互结合的一门新兴学科。本文从研究方法、农业施肥、农业种植制度、生态防治及应用展望等方面对土壤微生物生态学的应用研究现状作了综述,加强土壤微生物生态学在农作物生长和调控应用等领域的研究具有巨大的潜在应用前景和重要意义。     

土壤微生物多样性实验研究方法概述

对有关土壤微生物多样性,包括微生物类群多样性、群落结构多样性、功能多样性以及基因多样性等的描述与表征方法进行了探讨,同时,对当前国内外土壤微生物多样性的一些实验研究方法,包括土壤微生物分离培养方法、Biolog 微平板方法、FAME 分析方法和分子生物学方法等进行了介绍和评述。并指出在土壤微生物多样性研究中,如果可能的话,需要将各种方法结合起来使用,方可得到有关土壤生物多样性的较为全面的信息和理解。     

碳酸钙和根际作用对酸性红壤解磷微生物丰度的影响

选用玉米品种郑单958为试验材料,设置不添加碳酸钙(CK)、每千克土添加0.3g碳酸钙(Ca-0.3)和0.5g碳酸钙(Ca-0.5)3个碳酸钙处理,以相应处理未种植物土壤为非根际对照土壤,研究了碳酸钙和根际作用对酸性红壤磷酸酶活性及解磷微生物相关功能基因phoC和phoD丰度的影响。结果表明:碳酸钙添加能有效改善玉米生长,促进地上部氮、磷、钾和钙的吸收。土壤酸性磷酸酶(ACP)活性显著高于碱性磷酸酶(ALP)活性,表明酸性土壤中ACP在矿化有机磷方面占主导地位。根际土壤ACP、ALP活性和phoD基因拷贝数均显著高于非根际,而仅Ca-0.5处理ALP活性和phoD基因拷贝数显著高于CK,说明根际效应强于碳酸钙处理。phoC基因拷贝数与土壤铵态氮、硝态氮含量存在显著相关性,ALP活性和phoD基因拷贝数与土壤pH及铵态氮、硝态氮、有效磷、交换性钙含量均存在显著相关性。可见,碳酸钙和根际作用均影响酸性土壤解磷微生物功能和丰度,但根际效应更加明显,这些作用与土壤理化因子的改变密切相关。     

土壤频繁应用杀虫剂的降解动力学统一模型

This paper deduces a kinetic model for microbial degradation of pesticides in soils:x=x0(M/[M-m0 m0exp(μt)])^kM/μ where x is the concentration of pestcide at time t,x0 the initial concentration of the pesticide,m0 the initial number of pesticide-degrading microogranisms,M the carrying capacity for the microorganisms,μ the specific growth rate of the microorganisms,and k the rate constant for the pesticide degradation.In periodic applications of pesticides,this model can be used to continumously describe every degradation curve.Whether a lag phase occurs or not,we can obtain the minimum residue of the pesticide(xe): xc=xdexp(-kMτ)/[1-exp(-kMτ)]where τ the regular time intervals between applications ,and xd the dosage of the pesticide.     

施肥对日光温室土壤微生物与酶活性变化的影响

在日光温室内,采用田间试验的方法,研究不同施肥处理对西红柿土壤酶活性和土壤微生物数量的影响。结果表明:施有机肥、化肥、有机肥 叶面肥处理土壤磷酸酶活性增加,施化肥 叶面肥处理比施化肥处理土壤磷酸酶活性增加;施有机肥处理土壤脲酶活性增强;施化肥 叶面肥处理土壤磷酸酶活性比施有机肥 叶面肥处理降低;施肥对蔗糖酶和过氧化氢酶活性的影响较小。施有机肥处理土壤细菌、真菌和放线菌数量增加,施化肥处理土壤细菌数量降低,土壤真菌和放线菌数量增加。     

根分泌物对根际微生物生态分布的影响

本文从根分泌概念着手 ,依据近 2 0年来国内外有关根分泌研究的一些成果 ,就根分泌物的概念、产生机制进行了综合论述 ,并重点讨论了植物根分泌物对根际微生物代谢、生态分布、病原微生物抑制作用的影响以及土壤环境对根分泌物的影响。     

Regulation of urease production in soil by microbial assimilation of nitrogen

Summary Studies of the effects of different forms of N on urease production in soils amended with organic C showed that although microbial activity, as measured by CO₂ production, was stimulated by the addition of NH₄ ⁺ or NO₃ ^- to C-amended soils (200 mol glucose-C g^–1 soil), urease production was repressed by these forms of N. The addition of L-methionine sulfoximine, an inhibitor of inorganic N assimilation by microorganisms, relieved the NH₄ ⁺ and NO₃ ^- repression of urease production in C-amended soil. The addition of sodium chlorate, an inhibitor of NO₃ ^- reduction to NH₄ ⁺ by microorganisms, relieved the NO₃ ^- repression of urease production, but did not eliminate the repression associated with NH₄ ⁺. These observations indicate that microbial production of urease in C-amended soils is not directly repressed by NH₄ ⁺ or NO₃ ^-, but by products formed by microbial assimilation of these forms of N. This conclusion is supported by our finding that the biologically active L-isomers of alanine, arginine, asparagine, aspartate, and glutamine, repressed urease production in C-amended soil, whereas the D-isomers of these amino acids had little or no influence on urease production. This work suggests that urease synthesis by soil microorganisms is controlled by the global N regulon.