Microbial and soil parameters in relation to N mineralization in soils of diverse genesis under differing management systems

 Oregon soils from various management and genetic histories were used in a greenhouse study to determine the relationships between soil chemical and biological parameters and the uptake of soil mineralized nitrogen (N) by ryegrass (Lolium perenne L.). The soils were tested for asparaginase, amidase, urease, β-glucosidase, and dipeptidase activities and fluorescein diacetate hydrolysis. Microbial biomass carbon (C) and N as well as metabolic diversity using Biolog GN plates were measured, as were total soil N and C, pH, and absorbance of soil extracts at 270 nm and 210 nm. Potentially mineralizable N (N₀) and the mineralization rate constant (k) were calculated using a first order nonlinear regression model and these coefficients were used to calculate the initial potential rate of N mineralization (N₀ k). Except for Biolog GN plates, the other parameters were highly correlated to mineralized N uptake and each other. A model using total soil N and β-glucosidase as parameters provided the best predictor of mineralized N uptake by ryegrass (R ² =0.83). Chemical and biological parameters of soils with the same history of formation but under different management systems differed significantly from each other in most cases. The calculated values of the initial potential rate of mineralization in some cases revealed management differences within the same soil types. The results showed that management of soils is readily reflected in certain soil chemical and biological indicators and that some biological tests may be useful in predicting N mineralization in soils. Received: 31 January 1997     

红壤区油茶根际解磷细菌的筛选、鉴定及其解磷能力

研究油茶根际解无机磷细菌的解磷能力对提高红壤丘陵区土壤磷素利用效率具有重要的指导意义.本研究从油茶根际分离筛选出97株具有解无机磷能力的菌株,采用NBRI-BPB培养基进行复筛获得5株解磷能力较强的解无机磷细菌,并测定其在NBRIP培养基中有效磷含量,采用形态特征、生理生化、Biolog系统和16SrDNA序列分析鉴定细菌种类,确定WB38为耳假单胞菌(Pseudomonas auricularis),WB39(WB75)为杓兰果胶杆菌(Pectobacterium cpripedii),WB53(WB68)为路德维希肠杆菌(Enterobacter ludwigii).研究了解磷菌株WB38在不同条件对解磷能力的影响,结果表明:不同因子对该菌株解磷能力均有显著影响,其中温度对其解磷能力影响最大;该菌株培养的最适碳源和氮源分别为葡萄糖和NH4NO3;解磷细菌WB38解磷的最佳培养条件为A2B1C1D1,即温度28℃,初始pH值6.5,接种量1％,溶氧量25 mL.     

Effects of sulfamethoxazole on soil microbial communities after adding substrate

The effect of the antibiotic sulfamethoxazole (SMX) on soil bacteria was studied using two methods (leucine incorporation and Biolog plates) of estimating pollution-induced community tolerance (PICT). SMX was added to an agricultural soil in a microcosm setup. The addition of different substrates (manure and alfalfa), and a non-amended soil, were also studied over 5 weeks. PICT measurements were validated by comparison with other measurements. Community structure was assessed using phospholipid fatty acid (PLFA) analysis and community-level physiological profiling (CLPP), and bacterial growth was estimated using leucine incorporation. Increased PICT was found at SMX concentrations of 20 and 500 mg SMX kg⁻¹ soil in samples containing manure and alfalfa, and at 500 mg SMX kg⁻¹ soil in non-amended soil (only concentration tested) using leucine incorporation. No effect was seen at 1 mg SMX kg⁻¹ soil. It was not necessary to add any substrate to increase the microbial activity in order to detect the effects of a bacteriostatic toxicant such as SMX when using measures based on bacterial growth. Direct inhibition of bacterial growth 2 days after SMX addition was correlated to PICT. No major changes in PICT due to SMX addition were found when using Biolog plates. However, there was a tendency towards increased PICT at the higher SMX concentrations in the manure-amended soil. Thus, different methods of detecting PICT have different sensitivities in detecting the toxic effects of SMX. The effects of substrate amendment were reflected by changes in the microbial community, estimated using both PLFA and CLPP. SMX was found to have a clear effect at the two highest levels of SMX in the manure- and alfalfa-amended soils, with an increase in fungal and a decrease in bacterial PLFAs. Little difference in the PLFA composition was found in the non-amended soil. CLPP was only affected at the highest SMX concentration. Although different variables showed different sensitivities to the effects of SMX, the results were consistent with an initial decrease in bacterial growth rates of sensitive species, which eventually transformed into more tolerant species, altering the community composition.     

含油污泥的堆肥处理对微生物群落结构的影响

采用堆肥方法处理含油污泥,评价堆肥处理对含油污泥中石油烃的去除效果,并采用Biolog方法和构建16SrRNA基因克隆文库的方法对处理过程中微生物碳源利用特征和微生物群落结构进行了研究。结果表明,含油污泥经过90d的堆肥处理,石油烃降解率达53.3%±9.5%,显著高于对照处理。堆肥处理可以显著促进石油烃降解,是一种处理含油污泥的有效措施。Biolog分析结果表明,堆肥处理的孔的平均颜色变化率（AWCD）显著高于对照处理,堆肥处理提高了土壤微生物代谢活性。主成分分析结果表明,对照处理和堆肥处理的微生物碳源利用特征明显不同,堆肥处理改变了含油污泥中微生物的代谢功能特征。对照处理和堆肥处理的16SrRNA基因克隆文库之间存在显著差异,对照处理的优势类群是γ-Proteobacteria,堆肥处理的优势类群是Bacteroidetes,堆肥处理显著改变了含油污泥中的微生物群落结构。Marinobacter和Alcanivorax是对照处理中的优势菌,可能与石油烃的自然降解过程有关,而Pusillimonas和Agrobacterium可能对堆肥处理中石油烃的降解起一定作用。     

河南鸡公山自然保护区典型森林类型土壤微生物群落功能多样性

Biolog EcoTM微平板技术是研究微生物群水平多样性的一种重要方法。通过该方法对河南鸡公山自然保护区3种主要森林类型(落叶阔叶林、针阔混交林、杉木林)的土壤微生物群落多样性进行研究,结果显示:土壤微生物对单一碳源利用强度随着培养时间的增加呈递增的趋势,落叶阔叶林土壤微生物活性高于其他两种森林类型。3种森林类型土壤微生物对碳源利用差异性显著(p<0.01),森林植被类型直接影响土壤微生物功能多样性。分析表明,氨基酸是研究区域森林土壤微生物敏感碳源。     

不同农业措施对草莓连作土壤微生物群落特征的影响

[目的]探讨不同农业措施对草莓连作土壤微生物区系、活性、功能多样性及酶活性的影响。[方法]通过田间小区试验,利用土壤酶学方法、微生物培养方法和Biolog微生物自动分析系统,分析了土壤微生物群落特征。[结果]与不施肥相比,莓-稻水旱轮作、米糠＋日晒和石灰氮均显著提高草莓连作土壤细菌所占比例、细菌/真菌、土壤微生物总数、AWCD、土壤脱氢酶活性、Shannon指数、Simpson指数和Mcintosh指数;莓-稻水旱轮作和米糠＋日晒还能提高土壤脲酶活性。与习惯施肥相比,莓-稻水旱轮作、米糠＋日晒可显著提高草莓连作土壤AWCD、Mcintosh指数,莓-稻水旱轮作和米糠＋日晒分别显著提高土壤脲酶和脱氢酶的活性。主成分分析表明,莓-稻水旱轮作、米糠＋日晒和石灰氮条件下草莓连作土壤微生物群落碳源利用特征与习惯施肥及不施肥显著不同。[结论]莓-稻水旱轮作和米糠＋日晒是控制草莓连作土壤生物退化的有效农业措施。     

Effects of glyphosate on rhizosphere soil microbial communities under two different plant compositions by cultivation-dependent and -independent methodologies

We studied, under two different plant compositions, the short-term effects of glyphosate on rhizosphere soil microbial communities through the utilization of cultivation-dependent and -independent techniques. A short-term pot study was carried out using factorial treatments that included two different compositions of forage plant species (triticale versus a mixture of triticale and pea) and two concentrations of glyphosate (50 and 500 mg active ingredient kg⁻¹ soil, as a commercial formulation, Roundup Plus) arranged in a completely randomized design experiment with four replicates. Control plants (no glyphosate added) were clipped in an attempt to compare two methods of weed control (manual = clipping; chemical = herbicide treatment). Rhizosphere soil was sampled 15 and 30 days after glyphosate treatment and the following soil components were determined: potentially mineralizable nitrogen, ammonium content, community-level physiological profiles using Biolog Ecoplates™, DNA microbial biomass and genotype diversity by means of PCR-DGGE. Fifteen days after herbicide treatment, a glyphosate-induced stimulation of the activity and functional diversity of the cultivable portion of the heterotrophic soil microbial community was observed, most likely due to glyphosate acting as an available source of C, N and P. On the other hand, 30 days after herbicide treatment, both the activity and diversity of the rhizosphere soil microbial communities showed an inconsistent response to glyphosate addition. Apart from its intended effect on plants, glyphosate had non-target effects on the rhizosphere soil microbial community which were, interestingly, more enhanced in triticale than in “triticale + pea” pots. Biolog™ was more sensitive than PCR-DGGE to detect changes in soil microbial communities induced by glyphosate and plant composition.     

转基因大豆对根际土壤微生物群落功能多样性的影响

采用大田试验结合Biolog技术比较分析了种植转基因大豆PAT与其亲本PAT1、转基因大豆ALS与其亲本ALS1及当地主栽大豆中黄13对根际土壤微生物群落功能多样性的影响。结果表明,由平均颜色变化率(AWCD)反映的土壤微生物活性呈现以下变化规律:在整个温育过程中,两种转基因大豆根际土壤微生物活性均高于相应亲本,当地品种中黄13根际土壤微生物活性介于转基因大豆和非转基因亲本大豆之间;两种转基因大豆根际土壤微生物群落物种均一度(J)和优势度指数(D)较对应亲本均无显著差异(P>0.05),转基因大豆PAT根际土壤微生物群落香农-维纳指数(H)与亲本相比差异不显著(P>0.05),而转基因大豆ALS根际土壤微生物群落香农-维纳指数(H)显著高于其亲本ALS1(P<0.05)。主成分分析结果表明,转基因大豆PAT、亲本PAT1、非转基因亲本大豆ALS1以及中黄13土壤微生物群落碳源利用类型相似,仅转基因大豆ALS土壤微生物碳源利用类型表现出差异。对不同碳源的分析结果表明,土壤微生物利用的主要碳源为糖类、氨基酸类、羧酸类和聚合物。     

Biolog方法在区分城市土壤与农村土壤微生物特性上的应用

通过利用环境微生物研究中比较可靠有效的Biolog方法研究了英国阿伯丁市城市土壤与邻近农村土壤的微生物群落结构和功能多样性,结果表明在重金属元素胁迫下,城市土壤的微生物群落结构与农村土壤相比已经发生了显著的改变,从而导致城市土壤微生物在利用能源碳方面包括消耗量、消耗速度、能源碳的利用种类等发生了一系列改变,使城市土壤显著区别于农村土壤。     

Characterization of soil microbial communities under different potato cropping systems by microbial population dynamics, substrate utilization, and fatty acid profiles

The effects of 11 different 2- and 3-yr potato crop rotations on soil microbial communities were characterized over three field seasons using several techniques. Assessments included microbial populations determined by soil dilution plate counts on various general and selective culture media, microbial activity by fluorescein diacetate (FDA) hydrolysis, single carbon source substrate utilization (SU) profiles, and fatty acid methyl ester (FAME) profiles. Potato rotation crops evaluated in research plots at Newport, ME, included barley/clover, canola, green bean, millet, soybean, sweet corn, and a continuous potato control. Soil populations of culturable bacteria and overall microbial activity tended to be highest following barley, canola, and sweet corn rotations, and lowest with continuous potato. Differences among rotations were less apparent during the potato phase of the rotations. Populations of actinomycetes and fluorescent pseudomonads tended to be greater in barley rotations than in most other rotations. SU profiles derived from BIOLOG GN2 plates indicated that certain rotations, including barley, canola, and sweet corn tended to have higher overall microbial activity, and barley and sweet corn rotations averaged higher substrate richness and diversity. Soybean and potato rotations tended to have lower substrate richness and diversity. Principal component analyses of SU data revealed differences among rotation soil communities in their utilization of individual carbon sources and substrate guilds, including carbohydrates, carboxylic acids, amines/amides, and amino acids. Analyses of soil FAME profiles demonstrated distinct differences among all the rotation soils in their relative composition of fatty acids, indicating differences in their microbial community structure. Fatty acids most responsible for differentiation among rotation soils included 16:1 ω5c, 16:1 ω7c, 18:2 ω6c, 18:1 ω9c, 12:0, and 13:0 anteiso, with 16:1 ω5c being the single greatest determinant. Overall, monounsaturated fatty acids, particularly 16:1 ω5c, were most prevalent in sweet corn rotations and polyunsaturates were highest in barley and millet rotations. Straight chain saturated fatty acids comprised the greatest proportion of fatty acids in soils under continuous potato. FAME biomarkers for microorganism groups indicated barley and millet rotations had the highest ratio of fungi to bacteria, and soybean and continuous potato had the lowest ratio. This research has demonstrated that different crop rotations have distinctive effects on soil microbial communities that are detectable using a variety of techniques. Further studies will identify more specific changes associated with particular rotations and relate these changes to potential effects on disease management, crop health, and crop productivity.