Impact of fertilizers on total microbiological flora in planted and unplanted soils of long-term fertilization experiment

Microbial population both in diversity as well as numbers in soil is influenced by the amount and type of various compounds entering soil through plant litter, root exudates and management factors like mineral and organic fertilizers under various climatic conditions. This in turn affects crop production and sustainability of soil health. Therefore, we tested total and number of various groups of microflora and also substrate use by Biolog to assess the metabolic capabilities of various groups of microbes from soils of long term fertilization experiment, Halle (Germany) having different mineral and organic fertilizer treatments in unplanted and planted soils with two crops viz., Secale cereale and Medicago sativa . High number of total microorganisms, nitrogen fixers and phosphate solubilizers were observed in the rhizosphere of Medicago sativa and Secale cereale compared to bulk soils. Microbial counts were specially higher in treatments of NPK+FYM (farmyard manure) and NPK in Secale. Medicago had more P solubilizers in yearly addition of phosphatic fertilizers compared to three yearly treatment. During substrate utilization test (Biolog) maximum utilization was found for sugars followed by amino acids in Secale whereas in Medicago sugars were followed by carboxylic acids.     

秦岭山区无机磷细菌筛选及其Biolog和分子生物学鉴定

为获得具有高解磷活性,可用于微生物肥料研制和生产的无机磷细菌菌株资源,采用平板溶磷圈法,从秦岭山区植物根际土壤样品中筛选获得3株高效无机磷细菌,命名为NO.9、NO.15、NO.17,根据钼锑抗比色法,培养5 d后,检测菌株发酵液,确定3株细菌的可溶性磷含量分别为98.12、80.37 mg/L和104.91 mg/L,微生物量磷含量分别为62.85、53.61、36.59 mg/L。生理生化特征、Biolog和16S rDNA鉴定结果表明,3株细菌均属于革兰氏阴性非肠道菌,NO.9菌株为Inquilinus ginsengisoli,NO.15菌株为醋酸钙不动杆菌(Acinetobacter calcoaceticus),NO.17菌株为荧光假单胞菌(Pseudomonas fluorescens)。     

生物复混肥对土壤微生物群落功能多样性的影响

在温室盆栽条件下,利用Biolog微平板技术,研究玉米施用无机复混肥、有机无机复混肥和生物复混肥后土壤微生物群落功能多样性的变化。结果表明,不同施肥处理土壤微生物群落AWCD、Shannon多样性指数(H)和Shannon均匀度指数(E)以生物复混肥处理最高,CK处理最低;土壤微生物群落利用6类碳源的能力随玉米生长期的延长而降低,但是中后期各处理的土壤微生物对6类碳源的利用率差异不显著,土壤微生物利用的碳源主要是糖类、多胺类、氨基酸类和多聚物类。土壤微生物群落主成分分析表明,不同处理土壤微生物碳源利用特征出现分异:生物复混肥处理主要分布在第1主成分正方向,其他处理主要分布于第1主成分的负方向,起分异作用的主要碳源是糖类、羧酸类和氨基酸类。生物复混肥处理能够提高土壤微生物代谢活性和土壤微生物群落功能多样性,无机肥和CK处理土壤微生物碳源利用特征相似。     

生防细菌C 3的鉴定及对魔芋软腐病的防效研究

从魔芋根际土壤中分离得到一株具有强烈抑菌活性,并具有较广抑菌谱的革兰氏阳性生防细菌菌株C3.经形态特征、常规生理生化特征和Biolog鉴定,发现该菌株与解淀粉芽孢杆菌Bacillus amyloliquefaciens特征很相似.采用细菌通用引物27f和1 492r扩增16SrDNA基因片段,得到1 105bp DNA片段,其序列与已报道的解淀粉芽孢杆菌FZB42的同源性高达100%,故将生防细菌菌株C3鉴定为解淀粉芽孢杆菌B.amyloliquefaciens.田间防效测试结果显示,在对照病情指数为41.20的情况下,生防细菌C3对魔芋细菌性软腐病的控制效果达到了57.76%.     

沙坡头生物结皮中微生物多样性初探

以沙坡头生物结皮(BSC)为研究对象,采用Biolog鉴定系统,通过碳源利用分析、功能多样性分析和聚类分析,对BSC微生物的多样性进行了研究。结果表明:BSC微生物群落代谢的平均颜色变化率(AWCD)在培养初期(0～24h)值很小处于适应期,中后期(24～168 h)AWCD值逐渐增强处于指数期,可能由于监测时间不是足够长,所以稳定期和衰亡期表现得不明显;BSC微生物能够利用羧酸类、聚合物类、碳水化合物类、酚类化合物类、氨基酸类和胺类6类碳源,其中对羧酸类碳源的利用率最高,对胺类碳源的利用率最低;BSC中微生物群落多样性指数为3.99,微生物群落均匀度指数为1.44;指纹聚类分析表明,当聚合水平>8.6时,BSC微生物可分为6类。研究表明,Biolog技术能够简便、快速、有效地反映BSC中的微生物活性及其变化情况。     

First isolation and characterization of Lactococcus garvieae from Brazilian Nile tilapia, Oreochromis niloticus (L.), and pintado, Pseudoplathystoma corruscans (Spix & Agassiz)

Lactococcus garvieae infection in cultured Nile tilapia, Oreochromis niloticus (L.), and pintado, Pseudoplathystoma corruscans (Spix & Agassiz), from Brazil is reported. The commercial bacterial identification system, Biolog Microlog^®, confirmed the identity of L. garvieae . Infectivity trials conducted in Nile tilapia using Brazilian Nile tilapia L. garvieae isolates resulted in a median lethal dose-50 of 1.4 × 10⁵ colony-forming units (CFU)/fish. This is the first evidence of the presence of this pathogen from Brazilian fish. In addition, this is the first report of L. garvieae infection in either Nile tilapia or pintado. Collectively, this evidence expands the geographical range of fish hosts, number of fish hosts harbouring L. garvieae and carbon source utilization by L. garvieae fish isolates. Furthermore, the Biolog system may be an alternative technique to polymerase chain reaction for the identification of L. garvieae and discrimination between closely related bacterial species.     

一株降解PCBs嗜盐菌的筛选及产酶条件研究

从深海底泥中提取出一株生长盐度在15％的降解PCBs的嗜盐菌，并将其命名为B2．6。此菌株能以PCBs为惟一碳源和能源生长．72h的降解率可达90％以上。对其进行了形态观察、革兰氏染色及各项生理生化指标鉴定，并和Biolog细菌鉴定系统鉴定的结果进行了比对。研究结果表明，菌株B2．6合成PCBs降解酶的模式为延续合成型；主族的一价离子Na^＋．K^＋能够提高PCBs降解酶的酶活，过渡金属离子Co^2＋, Mn^2＋, Cu^2＋, Fe^2＋和Fe^3＋酶活则有一定程度的抑制；此酶的最适温度和pH值分别为25～35℃和pH6-8。     

广东省不同区域菜园土壤微生物群落功能多样性比较

【目的】了解广东省不同区域菜园土壤微生物碳代谢功能群落结构的特点与差异.【方法】采用Biolog生态微平板方法分析广东的粤北、粤东、粤西和粤中4个不同区域菜园土壤微生物碳代谢群落结构.【结果和结论】4个不同区域的土壤微生物平均颜色变化率(AWCD)、Shannon指数、Simpson指数、Mc Intosh指数变化趋势均不同,反映微生物活性的AWCD表现为:粤北粤东粤西粤中,表明不同区域菜园土壤微生物在碳源利用能力、微生物丰度等方面存在差异.4个区域土壤微生物对6类31种碳源的利用程度存在差异;主成分分析显示,4个区域土壤微生物代谢基质主成分1的贡献率为54.76%,主成分2为13.25%;主成分1载荷0.18以上的基质有22种,主成分2有15种;碳源在主成分分离中起主要贡献作用的是氨基酸类、羧酸类、酚类和碳水化合物类碳源.表明不同区域菜园土壤微生物群落碳源利用模式及代谢功能不同,即土壤微生物群落功能多样性有差异.     

Assessing CLPPs using MicroResp™

Background, Aims and Scope  Soil microbial community diversity has been suggested as a way of assessing the ‘health’ or ‘quality’ of soils. While molecular (genetic) or biochemical (phenotypic) measurements of microbial diversity have their place, functional diversity is popular in that it relates to the activity of the soil microflora, particularly in the carbon cycle. Community Level Physiological Profiles (CLPPs) are usually assessed by carbon substrate utilization. The aim here is to review the various methods available for CLPP assessment. Main Features  The original method for CLPP determination was based upon the Biolog plate with its range of 95 carbon substrates and many studies have been employing this over the past 15 years. However, a number of criticisms have been leveled at the method, principally that it relies upon the growth of an extracted microbial population, which may not represent the true functioning of the whole soil. A multiple carbon-source, substrate induced respiration method (multi-SIR) was developed that did measure the response of the whole soil community without the need for growth but it did not have the convenience of the microtitre plate format. MicroResp™ was designed to overcome the deficiencies in both methods and we have applied it to a range of media including mineral and organic soils, sediments and litter. In addition we have adapted the method to the testing of a wide range of carbon substrates such as hydrocarbons, terpenes and pesticides. Results  The MicroResp™ technique covers the middle road of relevance and convenience, being a ‘whole soil’ method in a flexible microtitre plate format. It also has the advantage that it can be adapted for the use of radiolabelled (¹⁴C) substrates, which increases the specificity and sensitivity of the assay. A few direct comparisons between MicroResp™ have been made. We have found that its discriminatory ability compares favourably with Biolog while other users have reported it to be superior to the multiple SIR approach. A number of laboratories around the world are now utilizing MicroResp™ and reporting good sensitivity to changes to the microbial community due to such varied factors as age of forest rehabilitation, heavy metal treatment, hydrocarbon exposure, salinity, peatland vegetation, cropping system and tree clone type. Discussion  A comparison of the available methods reveals that each has its advantages and drawbacks. The choice of method may depend upon the particular hypotheses or questions. Conclusions  MicroResp™ offers a convenient, rapid and sensitive method for the determination of Community Level Physiological Profiles. Its application in a number of case studies has demonstrated its utility and advantages over other methods though its full potential for characterizing soil activity is yet to be realized. Perspectives  Increasing awareness of the environmental pressures on soils and the need to monitor soil health has resulted in a range of potential indicators. Microbial functional diversity is one such indicator that seeks to characterize a core soil attribute. The availability of rapid methods for its assessment will aid our understanding of such pressures on basic soil functioning. ESS-Submission Editor: Jizheng (Jim) He, PhD (jzhe@rcees.ac.cn)     

Impact of root herbivory by insect larvae on soil microbial communities

Bentgrass (Agrostis capillaris) and clover (Trifolium repens) were grown as pure swards and mixtures in pots containing soil from the NERC Soil Biodiversity field site located in Scotland. Six weeks after plant establishment leatherjacket larvae (Tipula paludosa) were added at field density to half the pots and the impacts of their feeding on plant shoot and root biomass and soil microbial communities was determined after 10 days. Plate counts and community level physiological profiles (CLPP) were used to characterise the microbial communities. Larval herbivory had a significant negative effect on shoot growth of both grass and clover and root biomass of grass. In mixed swards, larvae preferentially fed on clover. Soil microbial community structure was altered in the presence of larvae with populations of pseudomonads being significantly increased. These community differences may be attributed to increased quantity and qualitative changes in carbon flux to the soil as a result of root herbivory, as indicated by differences in the CLPPs of microbial communities in the presence and absence of larvae. This was mainly due to increased utilisation of some sugars, carboxylic and amino acids in the presence of larvae.