Characterization of Cu-resistant bacterial communities in Cu-contaminated soils

Bacterial communities in a spoil heap in a copper mine, a forest soil with high Cu contamination, and an agricultural soil with low Cu contamination were characterized in terms of Gram-staining, plasmid frequency, pigmentation, Cu-resistance system, and predominant Cu-resistant bacterial species. Similarity existed in that the ratio of green colonies for sorbing Cu and Gram-negative bacteria increased with the increase of the Cu content of the medium regardless of the characteristics of the bacterial communities. It was found that the plasmid was not present in most of the Cu-resistant bacteria of the soils. Curesistant genera including Burkholderia, Alcaligenes, and Methylobacterium species were isolated from the Cu contaminated soils using YG agar plates treated with 2 mM Cu. Furthermore, the bacterium with the highest Cu resistance (MIC = 5.5 mm Cu) was identified as a Gram-positive bacterium Bacillus sp., though most of the Cu-resistant bacteria were Gram-negative.     

生物黑炭对玉米苗期根际土壤氮素形态及相关微生物的影响

生物黑炭被作为土壤改良剂应用逐渐被认可,但其应用机制特别是生物黑炭对氮素形态和根际微生物的影响机理尚不明确,影响其推广。本文采用盆栽试验,研究了玉米和水稻秸秆烧制的生物黑炭按不同量施入土壤后,对玉米苗期株高、生物量和根际土壤氮素形态及相关微生物的影响。结果表明,施入60 g·kg-1玉米黑炭和40~60 g·kg-1水稻黑炭均对玉米苗期株高有显著(P0.05)降低作用,其中水稻黑炭的降低效果更为明显;分别施入60 g·kg-1玉米黑炭和20~60 g·kg-1水稻黑炭后,玉米植株地上部生物量均显著降低。施入60 g·kg-1玉米黑炭后根际土壤含水量和微生物量氮显著提高。随两种生物黑炭施入量的不断增加,玉米苗期根际土壤全氮、硝态氮含量以及固氮作用强度也显著增加,且均在60 g·kg-1施用量下达最大值。施用40 g·kg-1玉米黑炭可显著提高玉米苗期根际土壤氨态氮含量。同时,施用两种生物黑炭后,均不同程度地抑制了玉米根际土壤中细菌总体数量,促进了固氮菌和纤维素降解菌的生长,其中施入60 g·kg-1玉米黑炭的效果最为明显。综上,玉米和水稻秸秆生物黑炭的适量施用,可以促进玉米根际土壤氮素的循环转化,影响相关微生物的群落结构,且与水稻秸秆相比,玉米秸秆生物黑炭的施用效果更加明显。本文针对作物生长、土壤氮素形态及相关微生物数量3个方面研究生物黑炭施入土壤对氮有效性的影响,能够更全面、更准确地将生物黑炭如何影响土壤氮素转化展现出来,促进生物黑炭的深入开发利用,对黑土肥力保护具有一定意义。     

覆盖模式及小麦根系对土壤微生物区系的影响

采用平皿分离培养法研究了5种栽培模式和小麦根系对土壤细菌、真菌及放线菌数量的影响。连续2年的定位测定结果表明:覆膜有利于土壤微生物数量增加。5种栽培模式中,小麦根区、根外土壤细菌数量均以覆膜模式下最高,分别为116.8×106cfu·g-1和86.7×106cfu·g-1;土壤真菌和放线菌数量均以垄沟覆膜(垄上覆膜、垄沟播种)模式下最高,分别为3.0×103cfu·g-1、1.4×103cfu·g-1和18.9×105cfu·g-1、19.7×105cfu·g-1。不同模式下小麦根系对土壤细菌和真菌数量影响较大,表现为根区高于根外;而根系对放线菌影响较小,只有补灌和覆膜2种模式为根区高于根外。多重比较结果显示,覆膜与其他模式之间细菌数量差异极显著,根区土壤细菌和真菌数量与根外存在显著差异。覆盖和根系能大幅度增加根区细菌、真菌和放线菌的数量,强化小麦根区根外细菌和真菌的数量差异。     

Identification of organically bound iodine in soil humic substances by size exclusion chromatography / inductively coupled plasma mass spectrometry (SEC / ICP-MS)

Abstract

Sulfur transformation in riee rhizosphere was investigated. Soil enzyme arylsulfatase in rhizosphere and non-rhizosphere soil, whieh is responsible for mineralization of organic sulfur to sulfate sulfur, was studied. The Michaelis constants of arylsulfatase from Maahas c1ay and Pila c1ay loam were 3.04 × 10^-4 M and 3.97 × 10^-4 M, respectively. The arylsulfatase of rhizosphere soil showed higher activity than that of non-rhizosphere soil. Applieation of sulfate had no marked elTect on the enzyme aetivity either in rhizosphere or non-rhizosphere soil under the submerged condition. This indieates that arylsulfatase activity under the submerged condition is not inhibited by applieation of sulfate. The amount of HI-reducible sulfur in the rhizosphere and non-rhizosphere soi! inereased with time. However, rhizosphere soil had a higher amount of HI-reducible sulfur than did non-rhizosphere. Thc ditl'erence in arylsulfatase activity between the rhizosphcre and non-rhizosphere soil was not directly associated with thc number of sulfur-redueing and -oxidizing bacteria.     

Nitrification mineralisation and inorganic-N uptakein evergreen forests of the central Himalayas

Nitrogen mineralisation and available nitrogen (NO₃^– + NH₄⁺) in two evergreen forests species, viz. Quercus leucotrichophora and Pinus roxburghii, were examined. The plant available N ranged from 7.7–35.8 μg·g^–1·m^–1 with maximum values in March and minimum in November. The trend for N-mineralisation was opposite to that of the size of the available N-pool. N-Mineralisation rates ranged from 1.7–30.3 μg·g^–1·m^–1 within an annual cycle. Inorganic-N uptake was calculated for each incubated period, and for an entire year showed that in an oak forest site, nitrate-N was the dominant form of mineral nitrogen taken up by plants from soil. However, in a chir pine forest, nitrate-N and ammonium-N are equally taken up by plants from the soil. In both oak and pine forest sites, the nitrate-N uptake was maximum in the month of July and ranged between 2.4–11 μg·g^–1·m^–1 in the pine forest site and from 0–25 μg·g^–1·m^–1 in the oak forest site. In addition, ammonium-N varied from 0–12 μg·g^–1·m^–1 in the pine forest site and from 1–20 μg·g^–1·m^–1 in the oak forest site. N-Mineralisation was greater in N-rich forests and was moisture (soil) dependent and inversely related to bulk density.     

铜胁迫对白茅根际和非根际土壤酶活性影响的研究

通过盆栽实验研究了重金属Cu递进胁迫对白茅根际和非根际土壤酶活性的影响。结果表明,随着Cu浓度的增加,根际和非根际土壤的pH值下降、土壤酸化,而电导率呈持续上升,但根际土壤的pH值持续高于非根际土壤且更接近于中性。在梯度浓度的重金属Cu胁迫下,根际和非根际蔗糖酶活性随Cu浓度增加均表现出先升后降的趋势,但根际土壤的蔗糖酶活性在Cu浓度为1000 mg kg-1时达到峰值,而非根际土壤则在Cu浓度为500 mg kg-1时已到达峰值。白茅根际和非根际土壤中磷酸酶、脲酶和过氧化氢酶活性受Cu离子的影响均表现出持续下降的趋势,但各酶受抑制率各不相同。对梯度浓度Cu胁迫下的白茅根际和非根际土壤酶活性而言,四种酶在根际土壤中的活性普遍高于非根际土壤,且Cu2+对根际酶活性的抑制率也大于非根际土壤酶。对重金属单Cu污染敏感的土壤酶类依次为磷酸酶>蔗糖酶>脲酶>过氧化氢酶,其中磷酸酶可作为检测污染土壤的指示酶。     

Methods to evaluate pesticide damage to the biomass of the soil microflora

Respiratory methods to estimate the amount of C in the soil microbial biomass and the relative contributions of procaryotes and eucaryotes to the biomass were used to evaluate the influence of pesticides on the soil microflora. Experiments were conducted with 5 and 50 μg·g^?1 of three fungicides, captan, thiram and verdasan. At 5 μg·g^?1 they caused significant decreases (40%) in the biomass; the organomercury fungicide verdasan also caused a shift from fungal to bacterial dominance. Within 8 days, biomass in captan- and thiram-amended soils had recovered to that of the controls. Although the fungal to bacterial balance was restored in verdasan-amended soils, biomass recovery was not complete. At 50 μg·g^?1 the fungicides caused long-term decreases in the biomass and altered the relative proportions of the bacterial and fungal populations. Verdasan had the greatest effect on soil microbial biomass and composition.     

两株抗铜细菌的筛选、鉴定及对碳酸铜的溶解作用

本研究从长期受铜污染的铜矿废弃地土壤中分离得到两株对重金属铜具有较强抗性的菌株F16a和Fw17a。对菌株形态、生理生化特性及其16S rDNA系统进化进行分析,将F16a鉴定为肠杆菌属(Enterobacter),Fw17a鉴定为假单胞菌属(Pseudomona)。F16a和Fw17a对氨苄青霉素、头孢他啶均有抗性;此外,Fw17a还对氯霉素、四环素及低浓度的卡那霉素具有抗性。在有氮培养基(含500 mg/L CuCO3)液体培养48 h后,F16a使培养基上清液中铜浓度增加了300%左右;相反,Fw17a使培养基上清液中铜浓度降低了60%左右。     

黄土丘陵沟壑区典型林地土壤微生物、酶活性和养分特征

通过对陕西吴起县黄土沟壑区退耕还林地不同林分(沙棘、刺槐、油松、小叶杨)根际与非根际土壤养分、酶活性和微生物特征进行研究,比较4种典型林分及退耕草地“根际效应”及根际对养分的截留效应,评价根际效应对土壤特性产生不同改良效果,为黄土沟壑区退耕地人工林科学选择造林树种提供理论支持。研究表明:1根际与非根际土壤中有机质含量、有效磷含量、碱解氮含量和速效钾含量表现出显著差异,有机质、有效磷、速效钾含量均呈现明显的根际聚集现象。2根际土壤微生物数量和土壤酶活性总体高于非根际,仅油松样地中过氧化氢酶活性和小叶杨样地中脲酶活性根际低于非根际。3根际土壤中脲酶活性与细菌和真菌数量相关性达到显著水平,过氧化氢酶活性与真菌相关性达到显著水平;有机质含量与细菌、放线菌数量和脲酶活性相关性达到显著水平;碱解氮、有效磷含量均与细菌、真菌数量和脲酶活性相关性达到显著水平。在非根际土壤中,土壤养分含量与土壤微生物、土壤酶活性的相关性明显降低。4从土壤肥力综合水平看,根际土壤肥力水平综合得分总体上大于非根际土壤,其中根际土壤中沙棘小叶杨油松刺槐草地。沙棘能大幅度提高土壤肥力,具有较好的土壤改良效果。     

Responses of soil microbial communities to manure and biochar in wheat cultivation of a rice-wheat rotation agroecosystem in East China

Soil contamination in agroecosystems remains a global environmental problem. Biochar has been suggested as an organic amendment to alleviate soil pollution, sequester carbon(C), and improve soil fertility. However, information on how bacterial and fungal communities in acidic bulk and rhizosphere soils respond to swine manure and its biochar is still lacking. In this study, biochar and swine manure were applied at two rates of 1.5 and 3 t ha^-1 in a rice-wheat rotation field to assess ...     

稻鸭生态种养系统直播水稻根表和根际土壤营养特性研究

采用田间小区试验对比分析了直播方式下稻鸭生态种养系统和水稻单一种植系统水稻根表和根际土壤的氮、磷、钾和有机碳含量及pH的变化。结果表明:与水稻单一种植系统相比,稻鸭生态种养系统水稻根表和根际pH分别升高4.41%、0.85%,全氮含量分别降低0.11g·kg-1、0.11g·kg-1,全磷和全钾含量变化不明显。水稻根表速效氮和速效钾含量分别增加30.80mg·kg-1、17.93mg·kg-1,速效磷含量降低8.66mg·kg-1;水稻根际速效氮和速效钾含量分别减少15.13mg·kg-1、7.61mg·kg-1,速效磷增加9.66mg·kg-1。稻鸭生态种养系统水稻根表活性有机碳和高活性有机碳分别增加2.17g·kg-1、0.56g·kg-1,全有机碳含量减少0.99g·kg-1;根际土壤全有机碳、活性有机碳和中活性有机碳含量分别减少2.39g·kg-1、2.64g·kg-1、0.72g·kg-1。稻鸭生态种养改变了速效磷、速效钾和活性有机碳在水稻根域土壤的相对富集部位,即速效钾和活性有机碳富集部位主要在根表土壤,速效磷则主要在根际土壤。表明稻鸭生态种养明显改善了水稻根表和根际土壤营养状况,这可能对水稻根系吸收和利用土壤养分具有积极意义。     

间作五指毛桃土壤和根主要中微量元素含量及其相关性

为了解在成龄胶园间作的五指毛桃根际与非根际土壤及其根中主要中、微量元素含量情况，测定了实验区根际与非根际土壤各30个和对应五指毛桃根的钙、镁、铁、锰、铜和锌含量，分析了两者之间的关系，并评价了根际与非根际土壤中、微量元素丰缺状况。结果表明，非根际土壤钙、镁、铁、锰含量的平均值都高于根际土壤的，而铜、锌含量的平均值都低于根际土壤的。土壤钙、镁含量80%以上处于缺水平，而铁、锰含量处于丰或很丰水平，铜和锌含量处于适中水平。五指毛桃根际与非根际土壤中、微量元素存在空间上的广泛变异。五指毛桃根中、微量元素的平均值从大到小的排序是钙>镁>锰>铁>锌>铜。土壤中、微量元素与五指毛桃根中相对应的中、微量元素的相关性不强，且表现复杂。本研究结果揭示，在成龄胶园间作五指毛桃应当适量施用钙肥、镁肥和喷施一些铜元素叶面肥，并实行科学施肥，减少养分淋失。     

中国主要湖泊重金属来源及生态风险评估

探究外源有机酸对滇水金凤根际和非根际土壤中重金属解吸量和酶活性的影响,为滇池重金属污染修复提供理论依据。

模拟滇水金凤根系分泌物,研究不同浓度（0、0.005、0.01、0.05、0.1 mol L⁻¹）的乙酸、丙酸、丁酸、戊酸、酒石酸对滇水金凤根际和非根际土壤铅（Pb）、铜（Cu）、锌（Zn）解吸量和酶活性的影响。

5种有机酸均能显著促进土壤中Cu和Zn的解吸,且随有机酸浓度增加其解吸量增大,根际土壤中重金属解吸量大于非根际土壤。根际土壤中以0.1 mol L⁻¹丁酸对Pb、0.1 mol L⁻¹酒石酸对Cu和Zn的解吸量最大,分别为19.41、22.40和22.97 mg kg⁻¹。Cu和Zn的解吸分配系数（Kd）随5种有机酸浓度的增加而降低,Kd均在纯水处理时达最大值,分别为360.79和6592.64 L kg⁻¹;非根际土壤中仅0.1 mol L⁻¹丙酸能解吸Pb,乙酸浓度为0.005、0 mol L⁻¹时Cu、Zn的Kd最大,分别为11079.68、3452.75 L kg⁻¹。5种有机酸处理均能显著提高滇水金凤根际和非根际土壤中α-葡萄糖苷酶、β-葡萄糖苷酶、纤维二糖酶、木糖苷酶、乙酰氨基葡萄糖苷酶、亮氨酸氨基肽酶和磷酸酶活性,以0.1 mol L⁻¹戊酸、酒石酸分别处理根际和非根际土壤磷酸酶活性最高,分别为1181.88 ± 2.54和717.34 ± 6.64 nmol h⁻¹ g⁻¹。土壤酶活性与有机酸浓度、Cu和Zn解吸量呈极显著正相关（P < 0.01）,有机酸处理下滇水金凤根际土壤酶活性高于非根际土壤。

有机酸处理能增加滇水金凤根际和非根际土壤中Pb、Cu、Zn的解吸量和土壤酶活性,解吸后的重金属Cu、Zn能激活土壤酶活性。

     

铜胁迫对抗虫转基因水稻根际土壤微生物的影响

根际土壤微生物群落是联系土壤环境与作物生长的重要纽带,也是转基因作物环境安全评价的主要指标,而Cu胁迫对转基因水稻根际土壤微生物的影响目前尚不清楚。本研究基于盆栽试验,采用高通量测序等技术研究Cu胁迫(Cu含量100mg/kg)对抗虫转基因水稻华恢1号(HH)及其亲本非转基因水稻明恢63(MH)农艺性状及成熟期根际土壤微生物的影响,并以不施加Cu胁迫处理为对照。结果显示:Cu胁迫显著降低了水稻株高、生物量及产量;Cu胁迫改变了水稻根际土壤总氮、铵态氮含量及氧化还原电位值,而种植转基因水稻仅降低了根际土壤氧化还原电位值;Cu胁迫没有影响水稻根际土壤细菌丰度,但降低了细菌群落Alpha-多样性,改变了水稻根际土壤细菌群落组成和群落结构;相同Cu含量胁迫下,HH和MH水稻生长指标及根际土壤细菌群落结构及组成差异较小。上述研究表明,Cu胁迫抑制了水稻农艺性状及根际土壤细菌群落,但种植抗虫转基因水稻没有影响水稻植株及根际土壤细菌群落对Cu胁迫的抗性。     

Rhizosphere isoflavones (daidzein and genistein) levels and their relation to the microbial community structure of mono-cropped soybean soil in field and controlled conditions

Despite an increase in the understanding of the soybean isoflavones involved in root-colonizing symbioses, relatively little is known about their levels in the rhizosphere and their interactions with the soil microbial community. Based on a 13-year experiment of continuous soybean monocultures, in the present study we quantified isoflavones in the soybean rhizosphere and analyzed the soil microbial community structure by examining its phospholipid fatty acid (PLFA) profile. Two isoflavones, daidzein (7, 4′-dihydroxyisoflavone) and genistein (5,7,4′- trihydroxyisoflavone), were detected in the rhizosphere soil of soybean plants, with the concentrations in the field varying with duration of mono-cropping. Genistein concentrations ranged from 0.4 to 1.2 μg g⁻¹ dry soil over different years, while daidzein concentrations rarely exceeded 0.6 μg g⁻¹ dry soil. PLFA profiling showed that the signature lipid biomarkers of bacteria and fungi varied throughout the years of the study, particularly in mono-cropping year 2, and mono-cropping years 6-8. Principal component analysis clearly identified differences in the composition of PLFA during different years under mono-cropping. There was a positive correlation between the daidzein concentrations and soil fungi, whereas the genistein concentration showed a correlation with the total PLFA, fungi, bacteria, Gram (+) bacteria and aerobic bacteria in the soil microbial community. Both isoflavones were easily degraded in soil, resulting in short half-lives. Concentrations as small as 1 μg g⁻¹ dry soil were sufficient to elicit changes in microbial community structure. A discriminant analysis of PLFA patterns showed that changes in microbial community structures were induced by both the addition of daidzein or genistein and incubation time. We conclude that daidzein and genistein released into the soybean rhizosphere may act as allelochemicals in the interactions between root and soil microbial community in a long-term mono-cropped soybean field.     

基于高通量测序的两种植被恢复类型根际土壤细菌多样性研究

为研究库布齐沙地生态恢复过程中不同植被恢复类型土壤微生物细菌群落结构、多样性的变化特征,以流动沙地为对照,运用高通量测序技术,对自然恢复的油蒿群落、人工种植的中间锦鸡儿群落根际和非根际土壤细菌多样性进行了研究,并分析了土壤理化性质对其分布的影响。结果表明:(1)与流沙对照相比,两种植被恢复类型对细菌多样性产生了正效应,细菌群落丰度、多样性和均匀度明显增加。其中,自然恢复的油蒿群落土壤细菌丰度高于人工种植的中间锦鸡儿群落;(2)变形菌门、酸杆菌门和放线菌门为研究区土壤中的优势细菌类群,其中变形菌门在各样地丰度比例最高,变形菌的4个亚群变化趋势一致,α-变形菌相对含量在油蒿和中间锦鸡儿群落根际土壤中明显增加,尤其是自然恢复的油蒿群落根际土壤中α-变形菌得到了很好的恢复;(3)土壤有机质、全氮、速效氮、速效钾含量和土壤含水量是影响土壤细菌群落丰度和多样性的主要土壤因子,典型相关分析表明土壤有机质、全氮、全钾、速效钾、速效氮含量对于研究区土壤细菌群落遗传多样性的变化起着重要作用。     

The effect of rhizosphere of various plants on the growth of Rhizobium

As elucidated in the previous paper¹⁾, the rhizosphere of the host plant maintains more abundant root nodule bacteria than non-rhizosphere soil. The success of seed inoculation of the root nodule bacteria is supported by the multiplication in the vicinity of the host plant.     

几种植物在模拟污水处理湿地中根际微生物功能群特征的研究

以美人蕉、香蒲、垂穗莎草、玉带草为材料,研究了在模拟人工湿地条件下水生植物根际与非根际土壤中的微生物数量、种群、土壤酶活性特征。结果表明,不同水生植物根际、非根际间的细菌数量无明显差异,而真菌与放线菌的根际与非根际间差异较显著。根际硝化细菌数和反硝化细菌数最多的水生植物都是香蒲,分别为2．17×10^2 个·g-1干土和6．17×10^2个·g-1干土,有机磷细菌数最多的是美人蕉为5．68×10^4 个·g-1干土,无机磷细菌数最多的是玉带草为3．72×10^3 个·g-1干土。4种不同水生植物的根际土壤脲酶、磷酸酶、硝酸还原酶、亚硝酸还原酶活性都较非根际土壤高,湿地植物的根际效应显著。     

Additions of maize root mucilage to soil changed the structure of the bacterial community

The organic compounds released from roots (rhizodeposits) stimulate the growth of the rhizosphere microbial community. They may be responsible for the differences in the structure of the microbial communities commonly observed between the rhizosphere and the bulk soil. Rhizodeposits consists of a broad range of compounds including root mucilage. The aim of this study was to investigate if additions of maize root mucilage, at a rate of 70 μg C g⁻¹ day⁻¹ for 15 days, to an agricultural soil could affect the structure of the bacterial community. Mucilage additions moderately increased microbial C (+23% increase relative to control), which suggests that the turnover rate of microorganisms consuming this substrate was high. Consistent with this, the number of cultivable bacteria was enhanced by +450%. Catabolic (Biolog^® GN2) and 16S-23S intergenic spacer fingerprints exhibited significant differences between control and mucilage treatments. These data indicate that mucilage can affect both the metabolic and genetic structure of the bacterial community as shown by a greater catabolic potential for carbohydrates. We concluded that mucilage is likely to significantly contribute to differences in the structure of the bacterial communities present in the rhizosphere compared to the bulk soil.     

Impacts of soybean growth on Cu speciation and distribution in two rhizosphere soils

The effects of soybean growth on Cu speciation and distribution in two artificially Cu-contaminated soils (phaiozem, a Mollisol, and burozem, an Alfisol) were investigated using a rhizobox culture system followed by the sequential chemical extraction technique. The rhizosphere soils in the rhizobox were separated with nylon cloth into 11 sections: a central zone (4 mm in width) and ten side rhizosphere subzones (1 mm in width). The Cu fractions in Cu-contaminated phaiozem could be ranked as EXCH (exchangeable Cu)<ACID (HAc extractable Cu)< FeMnOX (bound to Fe–Mn oxides)<OM (bound to organic matter)<RES (residual Cu), and in Cu-contaminated burozem as EXCH< FeMnOX< OM< ACID< RES. Soybean growth resulted in an obvious increase of EXCH-Cu in the rhizosphere soil in the first 4 weeks of incubation, with the biggest increase in the central zone. Compared with the unplanted control soil, the content of ACID-Cu in soybean rhizosphere increased in the first 2–3 weeks of incubation and then decreased towards the end of the experiment (6 weeks). The increasing tendency was also observed in the FeMnOX-Cu fraction during the first 3 weeks and the OM-Cu fraction during the first 4 weeks, and their increments were obviously larger than those of the EXCH-Cu and ACID-Cu fractions. This suggested that more RES-Cu activated by the action of soybean roots was partitioned into the less phytoavailable forms, FeMnOX-Cu and OM-Cu. This may be of a benefit to the normal growth of soybean in Cu-contaminated soils. By the end of cultivation, the content of FeMnOX-Cu decreased, but only a small part of Cu was absorbed by soybean, being most of the Cu loss partitioned into the RES-Cu fraction.