Colonization strategy of Campylobacter jejuni results in persistent infection of the chicken gut

Although poultry meat is now recognized as the main source of Campylobacter jejuni gastroenteritis, little is known about the strategy used by the bacterium to colonize the chicken intestinal tract. In this study, the mechanism of C. jejuni colonization in chickens was studied using four human and four poultry isolates of C. jejuni. The C. jejuni strains were able to invade chicken primary cecal epithelial crypt cells in a predominantly microtubule-dependent way (five out of eight strains). Invasion of cecal epithelial cells was not accompanied by necrosis or apoptosis in the cell cultures, nor by intestinal inflammation in a cecal loop model. C. jejuni from human origin displayed a similar invasive profile compared to the poultry isolates. Invasiveness of the strains in vitro correlated with the magnitude of spleen colonization in C. jejuni inoculated chicks. The C. jejuni bacteria that invaded the epithelial cells were not able to proliferate intracellularly, but quickly evaded from the cells. In contrast, the C. jejuni strains were capable of replication in chicken intestinal mucus. These findings suggest a novel colonization mechanism by escaping rapid mucosal clearance through short-term epithelial invasion and evasion, combined with fast replication in the mucus.     

In vivo fish models for visualizing Aeromonas hydrophila invasion pathway using GFP as a biomarker

The invasion pathway of Aeromonas hydrophila in vivo was studied in Crucian carp (Carassius auratus gibelio) with a virulent strain A. hydrophila J-1 transformed with a plasmid encoding green fluorescent protein (pGFPuv) (A. h J-1^GFP), which had similar virulence characteristics (haemolysin, extracellular proteases production, toxicity for EPC cells, survival in fish serum and LD₅₀ value) as the parent strain. Fish were divided into four experimental groups: (1) normal fish; (2) bacteria bath challenged, unwounded fish; (3) skin artificially wounded by scalpel, bacterial bath challenged fish; and (4) skin mucus layer partially removed by paper towel, bacterial bath challenged fish. The number of bacteria from blood, gills, kidney, muscle, liver and intestine were detected at 2, 4, 8, 12, and 24 h post-challenge. High bacterial numbers were observed in the muscle of the artificial wound group, in the kidney of the mucus removed group and in the gills of all groups. In conclusion, the gills and damaged skin are likely to be the main routes of entry for A. hydrophila, and GFP can be used as a real-time biomarker to study intimate host–pathogen interaction in fish.     

我国林地外来有害植物发生现状及化学防除技术

当前国内外来有害植物,特别是杂草,造成的林业生产损失日益严重。本文概述了主要外来杂草的危害现状和入侵机制。在杂草治理的实践中,化学防除技术十分有效,并提出了杂草化学防除的技术措施。     

Patterns of nonindigenous herpetofaunal richness and biotic homogenization among Florida counties

Recent studies of geographic patterns of nonindigenous species richness suggest that a few key biogeographic and anthropogenic factors explain much of the variation in the richness of established species. It remains unknown, however, if the factors identified in these studies are taxon- and scale-specific or if general rules apply broadly across taxa and spatial scales. To address this issue, I used multiple regression analysis to identify factors that contribute significantly to variation in nonindigenous herpetofaunal richness at a relatively small spatial scale, the county level, in Florida, USA. Additionally, I used the Jaccard similarity index to determine if nonindigenous species affect the biotic similarity of the herpetofaunas of Floridian counties. In the regression analysis, county latitude strongly and negatively affected nonindigenous herpetofaunal richness, explaining approximately two-thirds of the variation in this variable. To a smaller degree, human population and university presence both related positively with nonindigenous herpetofaunal richness. Several other variables, including county land area, were not significantly related to nonindigenous herpetofaunal richness. The consistent importance of human population to nonindigenous species richness in this and past studies suggests that the influence of anthropogenic factors may be universal and are as or more important than the natural biogeographic factors that generally relate with native species richness. No evidence of overall homogenization was found based on Jaccard index values. However, a significant relationship between homogenization scores and distance between counties suggests that the effect of nonindigenous herpetofaunal richness on the similarity of county biotas is scale-dependent, such that adjacent counties tend to experience homogenization, while distant counties tend to experience differentiation as a result of the presence of nonindigenous herpetofauna. The results of this and similar studies may be useful in predicting the introduction and spread of nonindigenous species and in evaluating the effects of such introductions on native biodiversity.     

苹果蠹蛾入侵的影响因素及检疫调控措施

苹果蠹蛾是世界性重要的果树害虫之一,适应性广,危害严重,成为许多国家重要的检疫对象。为了更有效地防止苹果蠹蛾入侵中国主要水果产区,借鉴更安全环保的检疫处理和苹果蠹蛾发生区的控制措施,该文分析了苹果蠹蛾的传播途径和成功入侵的影响因素如寄主植物、温度、湿度、降雨和光周期等,并重点介绍了溴甲烷熏蒸、低氧空气或混合气体处理和高温低氧低温冷藏处理等检疫处理,以及性诱剂、苹果蠹蛾颗粒病毒和利用赤眼蜂等田间生物防治措施。苹果蠹蛾的成功入侵与寄主植物的种类有直接的关系,而气候条件则是影响其种群的重要因素。3种检疫处理措施均能安全有效地杀灭水果中苹果蠹蛾的不同虫态,而田间生物防治措施则能有效地控制苹果蠹蛾成虫、卵和幼虫3个重要的虫态,从而降低水果的损失。因此,这些结果为苹果蠹蛾的内外检疫和和田间控制提供了重要的参考。     

广东农业外来有害生物水葫芦入侵的历史阶段与特点简

水葫芦是在20世纪初期引进我国,于50年代作为畜禽青饲料而在全国各地广泛推广,广东地区最迟在50年代就已经有出现。水葫芦的大规模生长,会阻塞主要航道、破坏水生生态系统,威胁本地生物的多样性,对我国的经济、社会等造成巨大的损失。另一方面,水葫芦又是一种具有多功能的水生植物,可作为畜禽的青饲料、水田的绿肥、生产沼气的主要原料、作为食用菌的培养材料、编织产品的主要原料、作为人类的食用蔬菜,又可制作成为有机肥料、护肤产品、饮料,同时还具有较强的污水处理功能。     

外来入侵植物小子虉草研究进展与展望

入侵植物小子虉草(Phalaris minor Retz.)对入侵地冬春农作物,尤其是麦类作物危害严重,是世界公认的麦田恶性杂草。近年来,小子虉草在云南省大面积暴发危害,且种群不断扩张,严重威胁农田生态系统和粮食生产安全。然而,我国目前除作者前期开展了初步研究外,尚少见其他研究报道,给其预警与防控带来较大困难。本文根据国外近年来的研究进展和作者前期研究结果,首先综述目前小子虉草在世界的空间分布,从种间竞争、化感作用等方面分析其对农作物的危害原因;并从小子虉草的生物学特性、种群遗传特性、生态适应性以及入侵环境的可侵入性4个方面,综述分析其种群入侵扩张的成因,同时介绍了国外关于该入侵物种的防除方法。最后结合我国小子虉草的发生危害特点,提出今后的研究建议。本文通过介绍小子虉草的生物学与生态学特性和种群的入侵扩张机制,对该物种的早期预警、限制传播以及入侵生态系统的恢复与管理均具有重要的指导意义,也为相关决策者掌握了解小子虉草和制定安全有效的防控策略提供参考。     

Toad on the road: Use of roads as dispersal corridors by cane toads (Bufo marinus) at an invasion front in tropical Australia

Determining the factors that influence the rate of spread of invasive species is an important goal for conservation biology. If invasive species utilize specific landscape features as dispersal corridors, control programs can target such corridors. Radio-telemetry was used to determine landscape level factors that influence dispersal of an introduced anuran species (the cane toad) at an invasion front in tropical Australia. Most radio-tracked toads moved along roads and cleared fencelines, avoiding heavily vegetated habitat; they typically sheltered overnight close to these open corridors, returning to the road each evening to recommence dispersal. Surveys of the compass orientation of dispersing toads on roads showed that most animals were oriented along the main axis of the road (and thus, travelling along the road) rather than moving across it. To test the hypothesis that use of roads enables toads to disperse more rapidly than would be possible across more thickly vegetated sites, locomotor performance of toads was quantified under field conditions. As predicted, toads rapidly slowed down in dense roadside vegetation but continued to move rapidly through open areas. These results suggest that simple habitat manipulations of roadside verges might help to reduce the rate of dispersal of cane toads across tropical Australia.     

浙江省福寿螺入侵危害现状及防治方法研究进展

福寿螺作为一种世界性入侵生物,侵入浙江已近40年,由于其繁殖快、易扩散、适应性强和危害大,给全省农业生产和生态环境造成重大灾害。福寿螺在浙江省的入侵扩散大致经历三个阶段：第一阶段为20世纪80年代迅速扩张期;第二阶段为20世纪90年代至2010年前后扩散渗透期;第三阶段为2010年至今多点爆发期。福寿螺主要通过三种方式扩散,但扩散蔓延具有明显的局域性。福寿螺已由过去的点状分布发展成现今的片状分布,且入侵蔓延到全省11个地级市的所有县(市、区)。目前福寿螺的防治方法主要有农业防治、物理防治、生物防治、化学防治等,但尚未达到理想的效果。为应对福寿螺入侵危害的严峻形势,未来需加强福寿螺生态学、行为学、入侵生物学等基础研究,同时开展福寿螺危害的及时预测预警、应急防控、综合防控与资源化利用关键技术研究,逐步建立全方位综合防控技术体系。     

Management regimes for a plant invader differentially impact resident communities

Management of plant invaders causes disturbance and the compounding effects of both invasion and management on biodiversity merit rigorous assessment. We explored the impacts of both plant invasion and management disturbance in coastal dune communities of Australia invaded by the introduced shrub bitou bush (Chrysanthemoides monilifera ssp. rotundata). We compared the effects of intensive, manually based invader control with those of extensive control (mainly herbicide spraying from aircraft) across fore dune communities. We examined one management regime, which was typically intensive, in hind dune communities. Our main aim was to test the prediction that intensive methods would achieve better biodiversity outcomes than extensive approaches in fore dune communities. We found that extensive management created native species complements that diverged from non-invaded sites while intensive management approached non-invaded site conditions. However, intensively managed sites were also richer in other exotic species than extensively managed sites. Thus, while biodiversity outcomes were better under intensive management, the risk profile of such sites was increased by the greater array of exotics that could potentially replace the original invader. The positive effects of management evident on some fore dunes were not found in hind dunes, where managed sites had the highest exotic species richness and similar bitou bush seedling abundance as both non-invaded and bitou-invaded sites. Hind dune managed sites were also compositionally distinct from non-invaded sites. Thus fore and hind dune communities exhibited different responses to bitou management regimes.