The proline-activating activity of the multienzyme gramicidin S synthetase 2 can be recovered on a 115-kDa tryptic fragment

The multienzyme gramicidin S synthetase 2 was treated with trypsin to obtain fragments capable of activating proline. Three different active fragments were detected. The course of proteolysis was simulated by using a concentration range of trypsin; the cleavage pattern indicated that one of the fragments was particularly stable. This fragment was purified and shown to have a molecular mass of 115 kDa. It was compared chromatographically, by SDS/PAGE, and enzymatically to a Pro-activating fragment produced by a gramicidin-S-negative mutant. It can be concluded that the proteolytic fragment represents a structure which is contained on a continuous part of the polypeptide chain of gramicidin S synthetase 2 and has a relatively compact structure. This provides evidence that the multienzyme gramicidin S synthetase 2 is, at least in part, constructed from functional domains. An approach towards extending these studies to other parts of the gramicidin S synthetase 2 molecule has also been devised. This work complements recombinant DNA studies in the area, providing stable functional fragments.     

The contribution of symbiotic yeast to toxin resistance of the cigarette beetle (Lasioderma serricorne)

Representative plant allelochemicals were tested for toxicity to larvae of the cigarette beetle Lasioderma serricorne (F.) that were either untreated, treated with fungicides, or treated to render them free of symbiotic yeast (aposymbiotic) through surface sterilization of eggs. Insects rendered symbiont-free had higher mortality and/or developmental rates than controls when fed diets containing flavone, resorcinol or tannic acid. Fungicides reduced symbiont populations and/or caused morphological abnormalities. Two hydrolytic enzymes, which made up a significant protion of mycetome hydrolytic activity, were absent when symbionts were not present, as indicated by gel electrophoresis. This information indicates symbionts do contribute to the survival of their host by detoxifying toxins.

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Résumé La toxicité relative de substances allélochimiques végétales typiques a été examinée sur des larves de L. serricorne F. traitées aux fongicides et rendues aposymbiotiques par stérilisation superficielle des ufs. La toxicité de la nicotine est relativement inaffectée chez les larves aposymbiotiques; cependant les toxicités des resorcinol, flavone et acide tannique sont significativement augmentées chez les insectes ayant reçu un traitement pour éliminer leurs symbiontes. L'électrophorèse sur gel a montré que quelques enzymes responsables de l'hydrolyse du 1-naphthyl acétate, réaction enzymatique de la détoxification enzymatique, sont absentes chez les insectes aposymbiotiques. L'acide sorbique a réduit significativement l'effectif de symbiontes, tandis que le bénomyl a réduit leur gamme provoquant la multiplication anormale d'autres espèces. Ces résultats montrent que les symbiontes contribuent aux possibilités de détoxification de l'insecte. L'élimination des symbiontes peut être une technique efficace pour lutter contre les insectes qui en contiennent, puisqu'elle les priverait de leur contribution à l'alimentation et à la détoxification. Cette stratégie est vraisemblablement compatible avec des programmes de lutte intégrée, puisque les prédateurs et parasites ne contiennent pas de symbiontes.

     

农业部召开全国农业学校植物生态学教学讨论会

我国现有地区以上中等农业学校224所,分布全国各地,担负着全国中级农业科技人才的培养和县以下在职农业技术干部的轮训任务。实践证明,中等农业学校是我国初、高级农业教育和研究机构中承上启下的组成部分,是加速农业现代化建设的重要方面军。中等农业学校教育质量的高低,与专业基础课——植物及植物生理学教学质量的好坏是密切相关的。1980年5月农业部教育局颁布《植物及植物生理教学大纲》的     

Identification of Ly 5 on the surface of ‘natural killer’ cells in normal and athymic inbred mouse strains

This report that (1) cells mediating NK activity in different inbred mouse strains selectively express one of two allelic products specified by theLy-5 locus (or a locus tightly linked to it) and (2) this surface structure may directly contribute to NK-mediated cytolysis, since Ly 5 antiserum specifically inhibits NK activity in vitro in the absence of complement.     

Electrophysiological study of coupling between cultured cells of the mouse mammary gland in five distinct physiological states.

Electrical coupling has been observed between cultured cells of the mouse mammary gland in five distinct physiological or pathological states. We have employed young primary cultures of cells dissociated from the following tissues: normal glands from young virgin or midpregnant females, hyperplastic alveolar nodules (believed to be precancerous) transplanted in gland-free mammary fat pads, and spontaneous mammary adenocarcinomas and their pulmonary metastases. All successfully impaled pairs of cells (a total of 97 pairs) were found to be ionically coupled. Furthermore, in normal and tumor cell cultures, electrical coupling was observed between dome-dome and dome-nondome cell pairs. This study correlates with electronmicroscopic studies of fresh normal, hyperplastic, and tumor samples, which show the presence of gap junctions in all three.     

A Revision of the Cytology and Ontogeny of Several Deficiencies in the 3a1–3c6 Region of the X Chromosome of DROSOPHILA MELANOGASTER

The cytology and developmental attributes of 18 deficiency mutations in the 3A1–3C6 region of the salivary gland X chromosome of Drosophila melanogaster have been investigated. The cytological limits of several older deficiencies have been revised and clarified and several new deficiencies are characterized. The deficiency mutants, with one possible exception, show a lethal phase in the late embryonic period or the early first larval instar. In contrast, the earliest acting point mutation lethals exposed by these deficiencies generally exhibit a somewhat later, post-embryonic lethality, perhaps indicating that the deficiencies are having some cumulative or synergistic impact on development. However, even with this difference in time of lethality, it is still possible to conclude that it is not the absolute size of the deficiency but rather the character of the loci deleted that determines the impact on development. Observations on the morphology of lethal embryos shows that while this analysis is internally consistent, it does not agree with earlier work. None of the 3A1–3C6 deficiencies causes any major teratologies during embryogenesis. Furthermore, the "earliest acting" gene in this region does not lie in band 3C1 but is most likely associated with bands 3A8–10.     

拉恩氏菌W25对缓冲容量的响应及其产酸特性

【目的】进一步了解拉恩氏菌W25的溶磷机理和对土壤缓冲容量的响应。【方法】在液体摇瓶培养过程中,采用调节培养液pH的方法研究模拟土壤的缓冲容量对拉恩氏菌W25溶磷量的影响;通过单因子试验和HPLC相结合的方法,研究不同碳源、磷源条件下W25的溶磷能力及产酸特性。【结果】拉恩氏菌W25在磷酸三钙培养液中培养120 h后有效磷含量达到最大值,培养液有效磷含量与培养液pH变化之间呈极显著负相关性(P<0.01);W25在培养第48?96 h具有较强的缓冲能力,培养液有效磷含量加碱处理与未加碱处理差异不显著(P<0.05),从第120 h开始,缓冲能力开始减弱,在168 h后基本丧失了缓冲能力;W25在不同碳源条件下溶磷能力差异显著(P<0.05),依次为葡萄糖>乳糖>蔗糖>甘露醇>淀粉,不同磷源中培养液有效磷含量差异极显著(P<0.01),依次为磷酸三钙>磷酸铁>磷酸铝>磷矿粉;不同碳源、磷源条件下W25培养液中有机酸的种类和浓度差异较大,W25溶磷能力的大小不仅与产酸的种类有关,而且也与产酸的浓度有关。【结论】研究结果为更深入研究拉恩氏菌溶磷机理提供条件,为拉恩氏菌的应用提供理论基础。     

吲哚作为细菌细胞间信号分子的研究进展

吲哚广泛存在于自然界,目前已知超过145种革兰氏阳性和阴性细菌能产生吲哚,其中包括许多病原菌。随着细菌密度感应系统及其信号分子作用机制研究的深入,吲哚已被证实是肠道病原菌如致病性大肠杆菌、迟缓爱德华氏菌、霍乱弧菌等一类细胞间重要的信号分子,并参与细菌的多种生理活动,如毒力、抗药性、生物膜形成、运动性、质粒稳定性、抗酸性、孢子产生等。更为重要的是,吲哚及其衍生物还参与协调菌群竞争,有益于人体肠道菌群平衡和免疫系统。本文在吲哚作为细胞间信号分子参与迟缓爱德华氏菌的毒力、抗药性、生物膜形成和运动性的研究基础上,对近年来吲哚作为细菌细胞间信号分子的研究进展进行了综述。随着吲哚作用机制的进一步揭示,将有助于新型抗病原菌感染策略的研发和生物工程方面的应用。