Morphological characterization of the adherence and invasion of Streptococcus agalactiae to the intestinal mucosa of tilapia Oreochromis sp.: An in vitro model

Streptococcosis in tilapia Oreochromis sp. is possibly the most important bacterial disease for fish production worldwide. In Colombia, streptococcosis is caused by Streptococcus agalactiae (GBS), but in other countries, Streptococcus iniae is also involved. Prevention of streptococcosis is required and must be addressed for economic, social, international trade and public health reasons. This research used an in vitro culture of tilapia intestine to detail the intestinal mucosal response once the pathogen contacts the epithelium. We show that S. agalactiae sheds off its capsule to adhere to the epithelium. The bacterium adheres as a single individuum, in groups or in chains and is able to divide on the apical border of enterocytes. GBS adheres at and invades exclusively through the apical portion of the intestinal folds, using the transepithelial route. Once within the cytoplasm of enterocytes, the bacteria continue to divide. On the basolateral side of the epithelium, the microorganisms leave the cells to reach the propria and travel through the microcirculation. No evidence of an immuno‐inflammatory reaction or goblet cell response in the epithelium or the lamina propria was seen during the process of adherence and invasion of the pathogen.     

生物入侵生态学研究进展

概述了生物入侵的过程和途径、入侵机理及其生态学效应,在此基础上,提出了相关对策。     

福建省引种巨菌草Pennisetum sp.的生物安全性评价

通过分析引进巨菌草的引进途径、生物学特征、潜在危害、引进地的环境经济现状和管理现状等,并遵循重要性、系统性、实用性和可移植性的风险评估原则,建立了由1个目标层、5个准则层、20个指标层构成的引种巨菌草的风险评估体系;通过定量分析模型评估巨菌草在福建省的风险等级和水平.结果表明,引种巨菌草在福建省无入侵风险,可以引进或无须采取防范措施.本研究对菌草的安全引种、大规模种植与生产,提高其经济效益以及我国生物多样性保护具有重要意义.     

Impact of invasion of pine wood nematode on the growth of dominant shrub Pleioblastus amarus in Pinus massoniana communities

When pine trees are invaded by pine wilt diseases, the severely infected pine trees will die and fall down, or they will be removed when found to be damaged by the disease. It gives rise to the invasion of other species in these empty niches originally occupied by pine trees, i.e., competing surrounding trees or understory shrubs will invade the empty niches during the following years. As a result, the spatial distribution and pattern of the main tree species in a pine forest will change, and a niche variety in the main population will occur. In the end, the direction of the succession and restoration of the pine forest ecosystem will be affected. In our study, a Pinus massoniana forest with the dominant shrub, Pleioblastus amarus, was invaded by pine wood nematode and was clear cut. Selecting this community as our research object, we studied the effect of the invasion of the pine wood nematode on the growth of the dominant shrub, P. amarus, in this Pinus massoniana forest. Our results show that, after the attacked pine trees were removed, the niche was occupied by Pleioblastus amarus and other shrubs, which benefited the growth of P. amarus to its climax. Growth of P. amarus at the climax stage was greater compared with the unhealthy pine forest and the control group.     

广东湛江红树林自然保护区及附近海岸 互花米草入侵与红树林保护*

对广东湛江红树林自然保护区范围内和周边区域的外来植物互花米草（Spartina alterniflora） 的生长分布进行了实地调查。结果显示,雷州半岛东、西海岸均有互花米草的分布,总面积达 12.6 hm2 , 徐闻海安新港码头是互花米草在中国大陆分布的最南端。调查发现,互花米草和乡土红树植物的生态位 重叠,虽然致密的红树林内未见互花米草的生长分布,但互花米草比乡土红树植物更耐淹水,表现为在 光滩前沿低潮位仅有互花米草的分布。鉴于互花米草在雷州半岛分布范围广、生境类型多样、扩散增长 迅速的现状,建议对互花米草应采取“早发现,早清除”的治理措施,并开展跟踪监测,及时掌握互花 米草的扩散动态。     

混播人工草地退化演替过程中杂草入侵和草地质量

调查了多年生黑麦草与白三叶混播人工草地在退化演替过程中的杂草种类及侵入量。结果表明 ,入侵杂草的地上生物量、密度和盖度随人工草地退化程度的加重呈明显上升趋势。草地质量显著下降。华蒲公英等 15种为入侵人工草地的主要杂草种类。     

我国植物检疫的现状与技术进展

随着我国经济的发展,植物检疫工作取得了长足进步。综述了我国检疫政策与国际规则的对接,监督管理模式的改革以及植物检疫对严防外来生物入侵、服务三农和对外贸易交往等方面发挥的重要作用;介绍了植物检疫在科学决策的研究,分子生物技术的应用和除害处理方法多样化等技术进展。     

Tracking an invader to its origins: the invasion case history of Crupina vulgaris

Summary Based on its Mediterranean origins and close relationship with other highly invasive Asteraceae species, Crupina vulgaris was declared a Federal Noxious Weed shortly after its discovery in Idaho in 1968. Twenty-two years later, surveys revealed over 25 500 ha infested with five separate populations in four states. Despite this expansion, no-one knew how this unlikely invader with its large seed was moving long distances or how it had escaped detection entering the country. The objectives of this study were to characterize the invasion history by estimating when, how, from where and how many times Crupina vulgaris was introduced in North America. Methods included molecular markers (random amplification of polymorphic DNA), distribution maps and historical sleuthing. Molecular markers linked all five North American populations with the Iberian Peninsula, with at least three colonization events. Distribution maps limited the area to northern Spain, where C. vulgaris occurs outside the range of Crupina crupinastrum . Site histories indicated four, perhaps five, successful introductions from northern Spain, associated with Basque sheepherders. Two remote sites (Lake Chelan, WA, and Modoc County, CA) had direct links with northern Spain from the 1950s into the 1970s. It appeared that the other introductions also occurred decades before the discovery dates. Detailed knowledge of individual invasion case histories is relevant for preventing future weed introductions and as a framework for future ecological investigations, such as effects of selection pressures during immigration or niche relationships in native and introduced habitats.     

Aspen structure and variability in Rocky Mountain National Park,Colorado, USA

Elk, fire and climate have influenced aspen populations in the Rocky Mountains, but mostly subjective studies have characterized these factors. A broad-scale perspective may shed new light on the status of aspen in the region. We collected field measurements of aspen (Populus tremuloides Michx.) patches encountered within 36 randomly located belt transects in 340 km² of Rocky Mountain National Park, Colorado, to quantify the aspen population. Aspen covered 5.6% of the area in the transects, much more than expected based on previously collected remotely sensed data. The distribution and structure of aspen patches were highly heterogeneous throughout the study area. Of the 123 aspen patches encountered in the 238 ha surveyed, all but one showed signs of elk browsing or had conifer species mixed with the aspen stems. No significant difference occurred in aspen basal area, density, regeneration, browsing of regeneration and patch size, between areas of concentrated elk use (elk winter range) and areas of dispersed elk use (elk summer range). Two-thirds of the aspen patches were mixed with conifer species. We concluded that the population of aspen in our study area is highly variable in structure and that, at a landscape-scale, evidence of elk browsing is widespread but evidence of aspen decline is not. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pathogenic characterization of Aeromonas salmonicida subsp. masoucida turbot isolate from China

Aeromonas salmonicida is a gram-negative bacterium that is the causative agent of furunculosis. An A. salmonicida strain was isolated from diseased turbot (Scophthalmus maximus) with the sign of furunculosis from North China. Based on vapA gene, the strain was further classified as A. salmonicida subsp. masoucida RZ6S-1. Culturing RZ6S-1 strain at high temperature (28°C) obtained the virulence attenuated strain RZ6S. Genome sequence comparison between the two strains revealed the loss of the type IV secretion system (T4SS) and type III secretion system (T3SS) from the native plasmid pAsmB-1 and pAsmC-1 of wild-type strain RZ6S-1, respectively. Further study demonstrated that the wild-type strain RZ6S-1, but not its derivative mutant RZ6S, can stimulate apoptosis. Elevated protein level of cleaved caspase-3 was detected from epithelioma papulosum cyprinid (EPC) cells infected with wild-type strain RZ6S-1 as compared with that infected with RZ6S strain. Meanwhile, the invasion of the mutant strain RZ6S was about 17-fold higher than the wild-type strain RZ6S-1, suggesting that some protein(s) from A. salmonicida subsp. masoucida RZ6S-1 suppress its invasion. The RZ6S mutant strain was attenuated, since its LD₅₀ is over 10,000 times higher compared to the wild-type strain as revealed in the turbot infection model.