烟草青枯病菌生理分化的研究

1996年～1997年从福建和贵州两省采集分离30个菌株，在田间分区组用21个菌株做接种鉴定。依据它们在一套鉴别品种上的反应，可以区分为致病力强弱不同的4个苗系群，其中Ⅰ群最弱，Ⅳ群最强。福建省以Ⅲ群首系占优势，出现频率75％，贵州省则以Ⅳ群苗系占优势，出现频率达76．9％，该苗系对K326品种有很强的致病力，这是导致近年来该省部分地方K326品种成片枯死的主要原因。生理生化反应测定表明，30个菌株均能利用3种双情和3种已醇，但在硝酸盐还原上显示出有能否产气的明显差异。30个菌株在L-酪氨酸培养基上均能产生褐色素，但产生的量有明显差异。细菌素测定表明，30个菌株对指示窗的拮抗率达83．3％。

我国南方甘薯品种资源抗瘟病鉴定研究

用不同菌系群（ Ⅰ～Ⅲ） 的薯瘟病菌对７８０ 份南方甘薯品种资源进行室内抗瘟性鉴定，并在此基础上选取抗瘟性较强的品种，再在不同菌系群（ Ⅰ～Ⅲ） 的类型田中进行鉴定。鉴定结果表明：室内和田间鉴定结论一致，但不同品种对不同菌系群的薯瘟菌抗性差异显著。７８０ 份南方甘薯品种资源中对Ⅰ群菌其抗性表现 Ｒ 的品种占５ ．２６ ％ ， Ｍ Ｒ 的占１０ ．２５ ％ ；对Ⅱ群菌表现 Ｒ 的品种占１ ．０３ ％ 、 Ｍ Ｒ 的占３ ．９７ ％ ；对Ⅲ群菌其抗性表现 Ｍ Ｒ 的仅占０ ．６４ ％ ，而没有表现 Ｒ 的品种。１２ 份抗瘟品种先在室内经不同菌系群的菌株接种后，置于不同菌系群的病田中进行生产力鉴定。鉴定结果表明：韭菜种、蕹菜种、青农２ 号、丰薯２ 号等４ 个甘薯品种既可作为抗源亲本又可直接在薯瘟区应用推广。

日本水稻白叶枯病研究历史和现状

水稻白叶枯病(Xanthomonas Oryzae)是使水稻产量遭受严重损失的重要病害之一,特别是在亚洲稻区,由于水稻的生产和消费占全世界的92％以上,因此可以想象由本病造成的损失更加严重。据估计,病害流行年,一般减产10—30％,严重的减产50％以上。 自从近年来农业经济体制迅速改革和加速实施现代化以来,随着人们对水稻的产量和质量的要求日益提高,一些促进高产的农艺措施,如增施氮肥、密植和换种。

农业简讯

印度将开展“豆类革命” 司马军 六十年代中期以来,印度曾先后开展了“绿色革命”(小麦、水稻)和“白色革命”(牛奶),并已取得了一定成就。现在,印度又准备开展一场“豆类革命”。农业科学家们费了十年时间,用苏联、地中海沿岸国家和印度的豆类品种杂交,培育出一批新品种,不但产量高,而且生产期短。

Cultural and luminescent Conditions of a Marine luminous Bacterium

Study of marine noctilucence in marine is important to fishery, environmental monitoring and military affairs. A luminous bacterial strain D2 was isolated from the marine sediment samples collected near Donghai Island in Zhanjiang, China. The primary cultural and luminescent conditions of luminous bacterium D2 which was identified as Vibrio sp. were determined in liquid culture. The results showed that pH 7.0, 35 ℃, with 2.0 % NaCI, were the best growth conditions, and pH5 - 6, 20℃, OD600 0.08, with 3.0 % NaCI, were the optimal luminescent conditions.

Probiotics in hepatology

The paper provides a basic review of intestinal microflora and its importance in liver diseases. The intestinal microflora has many important functions, above all to maintain the microbial barrier against established as well as potential pathogens. Furthermore, it influences the motility and perfusion of the intestinal wall, stimu- lates the intestinal immune system and therefore also the so-called common mucosal immune system, reducing bacterial translocation and producing vitamins. Immune homeostasis at mucosal level results from a controlled response to intestinal luminal antigens. In liver cirrhosis, there are many changes in its function, mostly an increase in bacterial overgrowth and translocation. In this review, probiotics and their indications in hepatology are generally discussed. According to recent knowledge, these preparations are indicated in clinical practice only for cases of hepatic encephalopathy. Probiotics are able to decrease the permeability of the intestinal wall, and decrease bacterial translocation and endotoxemia in animal models as well as in clinical studies, which is extremely important in the prevention of complications of liver cirrhosis and infection after liver transplantation. Probiotics could limit oxidative and inflammatory liver damage and, in some situations, improve the histological state, and thus non-alcoholic steatohepatitis could be considered as another possible indication.

What's hot in inflammatory bowel disease in 2011?

Ulcerative colitis and Crohn's disease(CD) are the two major forms of inflammatory bowel disease(IBD).In this highlight topic series of articles,the most recent advances in the IBD field are reviewed,especially the newly described cytokines,including the therapeutic implications for their manipulation.In addition,the interplay between the intestinal microbiota and the host is reviewed,including the role of defensins and dysbiosis in CD pathogenesis.Finally,the importance of the non immune systems such as endothelial cells and the hemostatic system are highlighted as new players in IBD pathogenesis.

Characterization and in-vivo evaluation of potential probiotics of the bacterial flora within the water column of a healthy shrimp larviculture system

A thorough understanding of the normal bacterial flora associated with shrimp larviculture systems contributes to probiotic screening and disease control. The bacterial community of the water column over a commercial Litopenaeus vannamei larval rearing run was characterized with both culture-dependent and culture-independent methods. A total of 27 phylotypes at the species level were isolated and identified based on 16S rDNA sequence analysis. Denaturing gradient gel electrophoresis （DGGE） analysis of the V3-V5 region of 16S rRNA genes showed a dynamic bacterial community with major changes occurred from stages zoea to mysis during the rearing run. The sequences retrieved were affiliated to four phyla, Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes, with the family Rhodobacteraceae being the most frequently recovered one. Subsequently, 13 representative strains conferred higher larval survival than the control when evaluated in the in-vivo experiments; in particular, three candidates, assigned to Phaeobacter sp., Arthrobacter sp., and Microbacteriurn sp., significantly improved larval survival （P〈0.05）. Therefore, the healthy shrimp larviculture system harbored a diverse and favorable bacterial flora, which contribute to larval development and are of great importance in exploiting novel probiotics.

Effects of Acetochlor and Methamidophos on Fungal Communities in Black Soils

Using plate counting and ergosterol assay, single and joint effects of acetochlor and methamidophos on the dynamicsof soil fungal population and total fungal biomass in the black soil zone of Northeast China were investigated. The resultsdemonstrated that acetochlor at high concentration levels (150 and 250 mg kg-1) had an acute and mostly chronic toxicityon both the soil fungal population and total fungal biomass, but at a low concentration (50 mg kg-1) generally had astimulating effect that was stronger with total fungal biomass than with the soil fungal population. Methamidophos ata high concentration level (250 mg kg-1) alone and almost all of its combinations with various dosages of acetochlorincreased the soil fungal population, whereas at most sampling dates with 250 mg methamidophos kg-1 soil, total fungalbiomass increased, but in combination with acetochlor it was decreased in the early period of incubation and then increased28 days after incubation. Thus, through measuring the number of colony forming unit of the soil fungal population alongwith the total fungal biomass, a better understanding on effects of agrochemicals on soil fungi could be made.

Lopingian mixed floras from Linxi Formation in Soron area,Inner Mongolia

A lot of well-preserved plants from the Linxi Formation are collected in the Soron area,Inner Mongolia,consisting of 34 species of 16 genera. They are Late Permian in age. The flora is characterized by a lot of Angaran plants,such as Paracalamites,Comia,Rhachiphyllum,Iniopteris,Rufloria,etc. Some Cathaysian elements,such as Lobatannularia lingulata,L. multifolia,Fascipteris Cathaysiantus,F. densata,Taeniopteris szei,Cladophlebis liulinensis and C. permica,are also mixed within the present flora. This indicates that the Soron of Inner Mongolia was located in the sector between the Angaran and Cathysian floristic provinces in Lopingian. It is beneficial for depicting the location and the evolution of the Solenker--Xar Moron suture zone in the phytogeographic view. The transmigration of tropical and subtropical Cathaysian plants to the north indicates that the Paleoasian Ocean was closed during the late Permian along the suture zone.

Intestinal microbiota in inflammatory bowel disease:Friend of foe?

Inflammatory bowel disease （IBD） arises from disruption of immune tolerance to the gut commensal microbiota, leading to chronic intestinal inflammation and mucosal damage in genetically predisposed hosts. In healthy individuals the intestinal microbiota have a symbiotic relationship with the host organism and possess important and unique functions, including a metabolic function （i.e. digestion of dietary compounds and xenobiotics, fermentation of undigestible carbohydrates with production of short chain fatty acids）, a mucosal barrier function （i.e. by inhibiting pathogen invasion and strengthening epithelial barrier integrity）, and an immune modula- tory function （i.e. mucosal immune system priming and maintenance of intestinal epithelium homeostasis）. A fine balance regulates the mechanism that allows co- existence of mammals with their commensal bacteria. In IBD this mechanism of immune tolerance is impaired because of several potential causative factors. The gut microbiota composition and activity of IBD patients are abnormal, with a decreased prevalence of dominant members of the human commensal microbiota （i.e. Clostridium IXa and IV groups, Bacteroides, bifldobacteria） and a concomitant increase in detrimental bacteria （i.e. sulphate-reducing bacteria, Escherichia coll. The observed dysbiosis is concomitant with defectiveinnate immunity and bacterial killing （i.e. reduced mucosal defensins and IgA, malfunctioning phagocytosis） and overaggressive adaptive immune response （due to ineffective regulatory T cells and antigen presenting cells）, which are considered the basis of IBD pathogen- esis. However, we still do not know how the interplay between these parameters causes the disease. Studies looking at gut microbial composition, epithelial integrity and mucosal immune markers in genotyped IBD populations are therefore warranted to shed light on this obscure pathogenesis.

Structural insights into the CRISPR-Cas-associated ribonuclease activity of Staphylococcus epidermidis Csm3 and Csm6

The Clustered Regularly Interspaced Short _Palindromic Repeats （CRISPR）-CRISPR-associated （Cas） system is an adaptive immune system in bacteria and archaea that resists exogenous invasion through nucleic acid-mediated cleavage. In the type III-A system, the Csm complex contains five effectors and a CRISPR RNA, which edits both single stranded RNA and double stranded DNA. It has recently been demonstrated that cyclic oligoadenylates （cOAs）, which are synthesized by the Csm complex, act as second messengers that bind and activate Csm6. Here, we report the crystal structures of Staphylococcus epiderrnidis Csm3 （SeCsm3） and an N-terminally truncated Csm6 （SeCsm6AN） at 2.26 and 2.0 A, respectively. The structure of SeCsm3 highly resembled previously reported Csm3 structures from other species; however, it provided novel observations allowing further enzyme characterization. The homodimeric SeCsm6AN folds into a compact structure. The dimerization of the HEPN domain leads to the formation of the ribonuclease active site, which is consistent with the reported Csm6 structures. Altogether, our studies provide a struc- tural view of the ribonuclease activity mediated by Csm3 and Csm6 of the type III-A CRISPR-Cas system.