昆虫病原线虫共生菌杀虫蛋白的研究进展

昆虫病原线虫共生菌杀虫蛋白对许多农业害虫都有很明显的毒杀作用,作为一种新型的具有开发潜力和应用前景的生物防治资源,已经引起科学家们的关注并成为国内外研究的热点之一.综述了昆虫病原线虫共生菌杀虫蛋白基因的结构和功能及其杀虫机制方面的研究进展.     

昆虫病原线虫共生菌杀虫毒素研究进展

对昆虫病原线虫共生菌杀虫毒素的种类、与口服毒性有关的杀虫毒素以及口服毒性与杀虫毒素基因的关系等研究进展进行了综述,并对未来的研究方向提出了作者的见解。     

昆虫病原线虫与其共生细菌共生关系的研究进展

昆虫病原斯氏和异小杆线虫与共生细菌的共生关系是这类线虫作为害虫生物防治因子的基础。从线虫共生细菌的信息、营养、抗菌和病原作用,以及线虫对共生细菌的保护和媒介作用综述昆虫病原线虫与其共生细菌的共生关系;描述这一共生关系的影响因子;同时,讨论了未来的研究方向和应用前景。     

昆虫病原线虫的共生细菌

昆虫病原线虫与其共生细菌二者互惠共生 :共生细菌需要昆虫病原线虫作为载体以寄生寄主昆虫并做为自己的营养来源 ,而昆虫病原线则需要依靠共生细菌来杀死昆虫。综述了共生细菌的病原作用、抗菌作用与杀虫作用 ,评述了共生细菌的基因工程进展 ,讨论了昆虫共生细菌在昆虫病原线虫致病性的作用。     

不同昆虫寄主对昆虫病原线虫共生菌的敏感性比较

用菜青虫、棉铃虫、甜菜夜蛾、玉米螟、粘虫、黄粉虫等 6种昆虫对 1 0株昆虫病原线虫共生菌进行了敏感性测定。结果表明 :供试菌株对 6种昆虫都有胃毒活性 ,不同菌株对同一种昆虫的毒力差别较大 ,同一菌株对不同昆虫差别也很大。 1 0株菌在 1 2 0h对菜青虫的校正死亡率和体重抑制率均最高 ,显然是最敏感的寄主。在 1 0株共生菌中 ,XenorhabdusnematophilaHB3 1 0 5 9菌株的胃毒活性最高。     

昆虫病原线虫共生细菌致病机理的研究进展

昆虫病原线虫共生细菌是寄生于昆虫病原线虫肠道内的一种细菌,革兰氏染色呈阴性,属肠杆菌科(Ｅｎｔｅｒｏｂａｃｔｅｒｉａｃｅａｅ)细菌[1]。它包含两个属———嗜线虫致病杆菌属(Ｘｅｎｏｒｈａｂｄｕｓ)和发光杆菌属(Ｐｈｏｔｏｒｈａｂｄｕｓ),它们分别与斯氏线虫(Ｓｔｅｉｎｅｒｎｅｍａ)和异小杆线虫(Ｈｅｔｅｒｏｒｈａｂｄｉｔｉｓ)共生。这两种线虫由于杀虫能力强,是最有应用潜力的昆虫病原线虫。它们之间的共生关系可以概括为:共生菌存在于线虫的肠道内,线虫携带共生菌进入寄主昆虫体内,并将共生菌释放到昆虫的血腔中;共生菌在昆…     

昆虫病原线虫共生细菌共生性的分子生物学研究进展

嗜线虫致病杆菌属Xenorhabdus和发光杆菌属Photorhabdus细菌隶属肠杆菌科Enterobacteriaceae,对多种害虫致病能力强,分别与斯氏属Steinernema和异小杆属Heterorhabditis昆虫病原线虫互惠共生。该两属共生细菌既存在对昆虫寄主的病原性,又存在与线虫寄主的共生性。共生细菌与其线虫寄主的共生性主要表现以下4方面：（1）细菌产生食物信号诱导滞育不取食的感染期线虫恢复;（2）细菌为线虫生长与繁殖提供营养;（3）细菌能于感染期线虫的肠道定殖与生长;（4）细菌产生杀线虫毒素杀死非共生线虫。本文综述了共生菌以上4方面的共生性及其相关的分子机制。     

昆虫病原线虫共生细菌的分子生物学鉴定

对来自全国各地的23个未鉴定的共生菌菌株和本室保存的5个菌株的部分16S rDNA序列进行PCR扩增和测序,与GenBank中已知种的共生菌及4个其它肠杆菌的同源序列比较,利用DNAstar软件绘制系统树,初步确定了这28个共生菌的分类地位。其中品系0396Y与Xenorhabdus bovineii的相似值为100%,可能是该种的一个品系;品系0312-4与X.beddingii的相似值为100%,可能是该种的一个品系。     

七种我国昆虫病原线虫共生菌的分离与鉴定

昆虫病原线虫共生菌是一类具有广阔发展前景的生物防治资源, 由于这类菌的分类鉴定工作起步晚, 存在分类混乱和不系统的现象, 在本土资源十分丰富的我国尤为突出。本文对本实验室分离的7个共生菌菌株进行了分类描述, 建立了以生理形态, 生化特征为分类基础, 结合16S rDNA序列分析的有效鉴定方法。     

Extracellular protease production fromXenorhabdus nematophilus, a symbiotic bacterium of entomopathogenic nematodes

Effects of nutrients and growth temperature on the production of an extracellular protease fromXenorhabdus nematophilus, a symbiotic bacterium of entomopathogenic nematodes were studied for batch culture. Tryptone and fructose were most effective nitrogen and carbon sources to produce high level of the protease within 24–28 hr of incubation. The stability of protease was poor during the incubation of the bacteria. The protease activity increased in parallel with cell growth then decreased significantly for extended culture periods of the bacteria over 48 hr at 22–30°C. Autolysis of the protease was not a major cause for the decreased protease activity since no decrease in the protease activity was observed for the whole culture broth of the bacteria which was stored up to 80 hr at 4°C.     

Immune defence components of Spodoptera exigua larvae against entomopathogenic nematodes and symbiotic bacteria

The current work investigated the immune response of Spodoptera exigua Hübner (Lepidoptera: Noctuidae) when challenged with two entomopathogenic nematodes (EPNs), Steinernema carpocapsae (Weiser) and Heterorhabditis bacteriophora (Poinar). The cellular and humoral defences were considered in this study. The haemocytes were observed around H. bacteriophora, but no haemocyte was found around S. carpocapsae. In larvae treated with H. bacteriophora and S. carpocapsae, total haemocyte counts (THCs) reached maximum levels at 4 and 12 hours post-injection (hpi), respectively, but decreased with the proliferation of symbiotic bacteria. In the humoral defence, there was no significant difference between EPNs on phenoloxidase (PO) activity. Phospholipase A₂ (PLA₂) and protease activity levels in the initial time post-injection were higher in the larvae treated with S. carpocapsae than in H. bacteriophora. In the following, the roles of symbiotic bacteria and axenic infective juveniles (IJs) in suppressing the immune system were studied separately. Maximum THC levels were observed in larvae treated with axenic nematodes and minimum THC levels were recorded in the live Xenorhabdus nematophila treatment. In the humoral defence, PLA₂ activity with axenic S. carpocapsae was suppressed at 4 hpi, while in monoxenic S. carpocapsae the PLA₂ level was increased to the maximum amount at 8 hpi. PO activity with monoxenic S. carpocapsae decreased gradually by 4 hpi; in live X. nematophila, it decreased from 0.5 to 16 hpi, while in axenic S. carpocapsae, it increased slowly from 0.5 to 16 hpi. The current work showed the synergistic effect of nematode and its bacterium in the suppression of the immune system and highlighted the role of the symbiont in inhibition of immune responses.     

昆虫病原线虫与环境生物、非生物因素关系的研究进展

昆虫病原线虫(Entomopathogenic nematodes)是业已商业化的昆虫寄生性天敌,对农林和卫生等重要害虫具有安全和有效的控制作用.这类线虫与环境生物和非生物因素存在密切的联系.影响昆虫病原线虫的环境生物因素包括同类线虫、共生细菌、寄主昆虫、寄生真菌以及其它昆虫病原物等;影响昆虫病原线虫的环境非生物因素主...     

Partial purification and characterization of an extracellular protease from<Emphasis Type="Italic">Xenorhabdus nematophilus</Emphasis>, a symbiotic bacterium isolated from an entomopathogenic nematode,<Emphasis Type="Italic">Steinernema glaseri</Emphasis>

Entomopathogenic nematodes are used for insect control. Herein, an extracellular protease was partially purified from a culture supernatant ofXenorhabdus nematophilus, a symbiotic bacterium of an entomopathogenic nematode,Steinernema glaseri, using precipitation with 80% v/v isopropyl alcohol followed by gel permeation chromatography with a packed Sephacryl S-300 HR media. The partially purified protease exhibited maximal activity at pH 7 in the presence of 1 mM CaCl₂. The protease was identified as a metallo-protease based on the inhibition of its activity by the metal chelating agent, EDTA.     

Insecticidal toxin fromXenorhabdus nematophilus, symbiotic bacterium associated with entomopathogenic nematodeSteinernema glaseri

Entomopathogenic nematodes are being used for insect control. We purified a toxin secreted by the insect-pathogenic bacterium,Xenorhabdus nematophilus, which lives in the gut of entomopathogenic nematodes. Culture broth ofX. nematophilus was separated by centrifugation and concentrated by ultrafiltration. The concentrated culture broth was applied to a DEAE Sephadex A-50 column, and proteins were eluted stepwise with increasing concentrations of KCl. Fractions with insect toxicity were further concentrated and then applied to a HPLC with a gel filtration column. The molecular weight of purified toxin was 39 kDa on SDS-PAGE, and Fourier transformed infrared (FTIR) spectroscopy indicated that this toxin could be a new protein exhibiting the characteristics of C=O stretching peak near 1650 cm⁻¹.     

人体共生菌及其抗菌分子研究进展

随着耐药细菌的出现和广泛传播,开发新型抗菌药迫在眉睫。分布在人体不同部位的共生菌能够产生多种抗菌分子以抑制病原菌的定植和感染。人体共生菌的抗菌分子为研发全新结构和作用机制的药物提供了潜在的资源宝库,随着生物信息学、合成生物学、基因组学等组学技术的进一步发展,对人体共生菌抗菌分子的挖掘也会更加深入,为解决耐药问题提供了有效的途径。文中回顾了目前所发现的人体共生菌产生的抗菌分子,并介绍了几种用于挖掘人体共生菌这一天然抗菌药物的资源宝库的方法。随着现代生物工程技术的发展,人体共生菌的抗菌分子将会得到更加全面、系统的探索和应用。     

昆虫病原线虫液体培养研究概况

综述昆虫病原线虫液体培养的研究概况。包括液体培养的研究历史,不同培养基组分对昆虫病原线虫产量的影响,营养源的选择,培养参数在昆虫病原线虫液体培养过程中的作用,感染期昆虫病原线虫脂肪酸含量,以及昆虫病原线虫应用前景等。