黑曲霉、荧光假单胞菌去除污水中重金属试验研究

将黑曲霉和荧光假单胞菌引入到传统的卡鲁塞尔氧化沟工艺模型中,参照规范中氧化沟的水力停留时间,分别选取12、16、20、24、28、32和36 h水力停留时间进行试验,研究了不同水力停留时间2种菌种对重金属Cd、Cr、Pb和Cu的吸附降解规律.对水力停留时间为36 h进行了接种对比试验研究.研究发现接种2种菌种后,当水力...     

Pine wilt disease: a short review of worldwide research

This article summarizes the results of the research papers presented at the International Symposium on pine wilt disease (IUFRO Working Party Meeting 4.04.03) held in July 2009, at Nanjing, China. The general topics covered were on pine wilt disease (PWD), its causal organism, the pinewood nematode (PWN) Bursaphelenchus xylophilus, plus other PWN-associated microorganisms that play a significant role in PWD such as bacteria (e.g. Pseudomonas fluorescens). Most of the papers that are reviewed are based on work on PWD-PWN in East Asia and Russia. Specific topics covered include: 1) the fundamental conceptions of PWD development, 2) pathogenicity, 3) host-parasite relationships including the histopathology of diseased conifers and the role of toxins from bacteria-nematode ecto-symbionts, 4) PWN life cycle and transmission, 5) B. xylophilus dissemination models, 6) associations (with other nematodes), 7) diagnostics, 8) quarantine and control of the PWN and 9) biocontrol of the PWN.     

竹炭固定化紫外诱变假单胞菌处理间甲酚废水的研究

用紫外光对假单胞菌株进行诱变,以竹炭为载体,将紫外诱变假单胞菌固定在竹炭上,用竹炭固定化紫外诱变假单胞菌处理间甲酚水样。考察竹炭固定化紫外诱变假单胞菌投加量和水样pH值对间甲酚去除的影响以及进水浓度随反应时间的变化关系,研究竹炭固定化紫外诱变假单胞菌去除间甲酚的反应动力学。结果表明:相对于原菌株,菌株经紫外诱变后,生长周期缩短了6h。经紫外照射120s的假单胞菌可以在竹炭表面及内部孔隙形成明显菌胶团,诱变菌在竹炭上所成的生物量明显较未经诱变菌增加。竹炭固定化紫外诱变假单胞菌能有效地去除水样中间甲酚。竹炭固定化紫外诱变假单胞菌投加量和水样pH值影响到间甲酚的去除效果,pH值在4～6时,间甲酚的去除效果较好。20g竹炭固定化紫外诱变假单胞菌处理100mL初始浓度50,100,120,150,180mg·L-1间甲酚模拟水样42h,去除率依次为90.9%,76.4%,72.9%,64.6%和49.7%。竹炭固定化紫外诱变假单胞菌对间甲酚的去除能较好地符合零级反应方程。     

桉树焦枯病和青枯病的分离鉴定与防治方法

简要概述了危害我国华南地区桉树产业发展的主要病害——桉树焦枯病和青枯病,介绍了两种病害的部分研究方法,分析了两种病害的防治方法及其研究方向,以期为相关研究提供借鉴。     

猕猴桃溃疡病生防芽孢杆菌B2的鉴定及应用

猕猴桃溃疡病是一种毁灭性细菌病害,该病发展迅速,防治难度大,严重制约了猕猴桃产业的发展。为找到一种有效防治该病的方法,针对化学防治易产生抗药性、污染环境、杀伤天敌等特点,从猕猴桃根际土壤中分离共获得25株芽孢杆菌,采用点菌法筛选出4株对猕猴桃溃疡病菌(Pseudomonas syringae pv.actinidiae)具有拮抗效果的菌株(抑菌圈直径达到5 mm以上),其中B2拮抗作用最强。根据菌落(体)形态特征、生理生化鉴定以及16S r DNA序列分析,初步鉴定B2为蜡样芽孢杆菌(Bacillus cereus)。将B2的发酵原液稀释成1×109cfu/m L的发酵液,并在此基础上依次配制50、100、500、1000、2000倍的稀释液,用于盆栽试验。盆栽试验采用喷雾法,30天后的防治效果分别达到了90.45%、86.52%、80.90%、67.98%、47.19%、15.73%,60天后尽管病斑有少量增加,旧病斑有所增大,但与对照相比,病斑增长速度明显减缓。大田试验结果证明,该菌具有较好的生防潜力,喷雾法选择B2发酵液的50倍稀释液,涂抹法选择B2发酵液的100倍稀释液,可有效降低猕猴桃溃疡病的危害。     

菠菜内生固氮菌的分离及其功能特性研究

内生固氮菌具有促生、病原菌的防治及生物固氮等作用,并且占据着植物组织内有利于营养供应和微环境适宜的生态位,是重要的微生物菌种资源。从菠菜根内分离筛选优势内生固氮菌7株,其中假单胞菌属(Pseudomonas)5株,红球菌属(Rhodococcus)和黄杆菌属(Flavobacterium)各1株。菌株Pseudomonas sp.BCE6和Pseudomonas sp.BC-E8固氮酶活性较高,分别为(13.19±0.32)和(12.11±0.96)C2H4nmol/(mg protein·h),与圆褐固氮菌(ACCC11103)的固氮酶活性具有极显著性差异(P0.01);菌株Pseudomonas sp.BC-E7具有固氮酶活性[(8.42±0.03)C2H4nmol/(mg protein·h)]、产IAA能力[(59.58±4.15)μg/m L]、ACC脱氨酶活性[(5.067±0.376)μmol/(mg protein·h)],拮抗立枯丝核菌ACCC36124(Rhizoctonia solani)、麦类赤霉病ACCC36272(Gibberella zeae)等4种常见土传病害。菠菜内生固氮菌Pseudomonas sp.BC-E7是一株多功能内生菌,具有较好的生产应用前景。     

低温热处理对超高温灭菌乳中假单胞菌脂肪酶的活性影响

通过分析不同因素对假单胞菌脂肪酶活性的影响以及假单胞菌脂肪酶活性与超高温灭菌(UHT)乳脂肪上浮的关系,研究了控制UHT乳中假单胞菌脂肪酶活性和延缓脂肪上浮现象的措施。结果表明pH值对假单胞菌脂肪酶的活性有显著性影响(P<0.01),50、55、60℃(20min)的低温热处理能显著降低假单胞菌脂肪酶的活性(P<0.01)。贮藏试验表明低温热处理对控制UHT乳在贮存过程中的假单胞菌脂肪酶活性水平(P<0.01)和脂肪上浮现象(P<0.05)有明显的作用,而55℃和15min的低温热处理对缓解UHT乳在贮藏过程中的脂肪上浮现象最为有效。     

Colonization of wheat seedling (Triticum aestivum) roots by Pseudomonas fluorescens and Bacillus subtilis

Summary Colonization patterns of Pseudomonas fluorescens and Bacillus subtilis on roots of wheat seedlings growing on water agar were studied qualitatively by replica printing and quantitatively by the plate count method. The results indicated a stronger colonization potential for P. fluorescens (up to 10⁷ cfu/cm root) than for B. subtilis (up to 10⁵ cfu/cm root). Although the numbers of both species were lower when inoculated together, the observed colonization patterns on the roots were comparable to those found with single inoculations. For none of these bacteria was active migration along the root surface in any direction observed, indicating that distal positions are reached mainly by a passive displacement on the root tip and elongating cells. Ecological implications of the observed phenomena are discussed.     

Influence of soil properties on the vertical movement of genetically-marked Pseudomonas fluorescens through large soil microcosms

Summary Vertical translocation of the introduced transposon Tn5-tagged Pseudomonas fluorescens cells was studies after irrigation of 50-cm long soil columns of loamy sand. The soil in the columns was slowly brought to saturation using groundwater, and enough water was then slowly added to permit collection of the percolated water. Introduced bacteria were transported to lower soil layers to a significantly higher degree in undisturbed soil cores than in repacked cores; water transport was hampered in both core types due to high soil bulk densities. Soil bulk density affected the degree of transport of the introduced cells; progressively more cells were translocated to deeper soil layers and into the percolation water at decreasing soil bulk densities. Repeated percolation of soil at a bulk density of 1.25 caused an increase in Tn5-tagged cell numbers in the lower soil layers and in the percolated water. Further, cells initially introduced into a dry (5.3% moisture) soil were translocated to a lesser extent than cells introduced into a wetter (13% moisture) soil. Finally, wheat roots enhanced the water-induced transport of introduced cells to the 40- and 50-cm deep soil layers and into the effluent, but not to the remaining soil layers. Large soil columns such as those used in the present study are useful in assessing the transport and survival of introduced bacterial cells in soils under a variety of simulated environmental conditions.     

Suppression of root-knot disease by Pseudomonas fluorescens CHA0 in tomato: importance of bacterial secondary metabolite, 2,4-diacetylpholoroglucinol

The antimicrobial metabolites 2,4-diacetylphloroglucinol (2,4-DAPG) and pyoluteorin contribute to the ability of Pseudomonas fluorescens strain CHA0 to control plant diseases caused by soil-borne pathogens. P. fluorescens strain CHA0 and its derivatives CHA89 (antibiotics-deficient) and CHA0/pME3424 (antibiotics overproducing) were investigated as potential biocontrol agents against Meloidogyne javanica the root-knot nematode. Exposure of root-knot nematode to culture filtrates of P. fluorescens under in vitro conditions significantly reduced egg hatch and caused substantial mortality of M. javanica juveniles. Nutrient broth yeast extract (NBY) medium amended with 2% (w/v) glucose or 1 mM EDTA markedly repressed hatch inhibition activity of the strain CHA0 but not that of CHA0/pME3424 or CHA89. On the other hand, NBY medium amended with glucose significantly enhanced nematicidal activity of the strain CHA0/pME3424. Neither glucose nor EDTA had an influence on the nematicidal activity of the strains CHA0 and CHA89. Under in vitro conditions, antibiotic overproducing strain CHA0/pME3424 and CHA0 expressed phl‘-’lacZ reporter gene but strain CHA89 did not. Expression of the reporter gene reflects actual production of DAPG. In general, CHA0/pME3424 expressed reporter gene to a greater extent compared to its wild type counterpart CHA0. Regardless of the bacterial strains, reporter gene expression was markedly enhanced when NBY medium was amended with glucose but EDTA had no such effect. A positive correlation between the degree of juvenile mortality and extent of phl‘-’lacZ reporter gene expression was also observed in vitro. Strain CHA0 produced zones of 4-6 mm on MM medium containing gelatin while strain CHA0/pME3424 and CHA89 did not. When MM medium containing gelatin was amended with 2% glucose of 1 mM EDTA size of haloes produced by the strain CHA0 reduced to 2 mm. Under glasshouse conditions aqueous cell suspension of the strains CHA0 or CHA0/pME3424 at various inoculum levels (10⁷, 10⁸ or 10⁹ cfu ml⁻¹) significantly reduced root-knot development. CHA89 caused significant reduction in galling when applied at 10⁹ cfu ml⁻¹. To better understand the mechanism of nematode suppression, split root bioassay was performed. Split-root experiments, that guarantee a spatial separation of inducing agent and a challenging pathogen, showed that soil treatment of one half of the root system with cell suspension of CHA0 or CHA0/pME3424 resulted in a significant systemic induced resistance leading to reduction of M. javanica infection of tomato roots in the non-baterized nematode treated half. The results clearly suggest that the antibiotic 2,4-DAPG from P. fluorescens CHA0 act as the inducing agents of systemic resistance in tomato roots. Populations of CHA0 and its derivatives declined progressively by 10-fold between first and fourth harvests (0-21 days after inoculation). However, bacterial populations increased at final harvest (28 days after application).