Bioluminescent tracking of colonization and clearance dynamics of plasmid-deficient Yersinia pestis strains in a mouse model of septicemic plague

Yersinia pestis 201 contains 4 plasmids pPCP1, pMT1, pCD1 and pCRY, but little is known about the effects of these plasmids on the dissemination of Y. pestis. We developed a plasmid-based luxCDABE bioreporter in Y. pestis 201, Y. pestis 201-pCD1⁺, Y. pestis 201-pMT1⁺, Y. pestis 201-pPCP1⁺, Y. pestis 201-pCRY⁺, Y. pestis 201-p⁻ and Yersinia pseudotuberculosis Pa36060 strains, and investigated their dissemination by bioluminescence imaging during primary septicemic plague in a mouse model. These strains mainly colonized the livers and spleens shortly after intravenous inoculation. Y. pestis 201-pMT1⁺ appeared to have a stronger ability to survive in the livers, spleens and blood, and to be more virulent than other plasmid-deficient strains. Y. pestis 201-pPCP1⁺ appeared to have a stronger ability to colonize lungs than other plasmid-deficient strains. Pa36060 has the strongest ability to colonize intestines and lungs. Y. pestis 201 has the strongest ability to survive in blood, and the strongest virulence. These results indicated that the plasmid pMT1 was an important determinant in the colonization of livers, spleens and blood, whereas the plasmid pPCP1 appeared to correlate with the colonization in lungs. The resistance to killing in mouse blood seemed to be the critical factor causing animal death.     

稻-鸭农作系统对稻田生物种群的影响

通过田间试验,研究了稻-鸭农作系统对稻田有关生物种群的影响.结果表明：稻鸭共育对稻田相关昆虫、杂草、病原菌等有害生物的发生和危害及天敌数量具有较大影响.与不养鸭相比,稻鸭共育后12 d和42 d, 水稻基部害虫飞虱及叶蝉的数量平均减少64.8%和78.5%;稻鸭共育后15 d和45 d,稻田杂草平均减少67.7%和98.1%;水稻分蘖高峰期和齐穗期的纹枯病病情指数分别降低了40.4%和62.0%.稻鸭共育还增加了稻田害虫天敌蜘蛛的数量,抑制了水稻害虫的危害.     

外来植物病虫害的危害性、传播途径及防治对策

论述外来植物病虫害的危害性和入侵传播途径,并提出相应的防治对策。     

Target-oriented dissemination of Beauveria bassiana conidia by the predators,Harmonia axyridis (Coleoptera: Coccinellidae) and Chrysoperla carnea (Neuroptera: Chrysopidae) for biocontrol of Myzus persicae

Dissemination of microbial biocontrol agents via predators may have advantages for safe spore dispersal to targeted pests with the added benefit of predation. A laboratory study was conducted to test the target-oriented dissemination of conidia of Beauveria bassiana using larvae of both the multicoloured Asian lady beetle (Harmonia axyridis) and common green lacewing (Chrysoperla carnea) for control of aphids. Maximum dry conidial attachment occurred within approximately 7 min after exposure. After release of the treated predators on leaves of Chinese cabbage, within 12 hours lacewing larvae dispersed 89% of the attached conidia while Asian lady beetles dispersed 93%. Both predators dispersed conidia up to 2.4 m from the release site. Leaf disk bioassays were conducted to compare two application methods; the dissemination of conidia of B. bassiana by predators and the direct application of conidial suspensions. Mortality in sprayed aphids was 91±2.1% compared to 88±2.1 and 84±4.2%, respectively, when conidia were disseminated by lacewings and lady beetles. Predation was not affected in treated lacewing larvae whereas there was a 20% reduction in predation by lady beetle larvae. It appears that B. bassiana can be effectively delivered using certain insect predators.     

在水生与气生状态下石莼光合作用对无机碳的响应

潮间带海藻光合作用总是处于水生(高潮时)与气生(低潮时)两种连续变化的环境状态下进行.对汕头沿岸常见的潮间带海藻石莼(Ulva lactuca L.)在水生和气生不同状态下光合作用对无机碳的响应特性进行了比较研究.在水生状态下,现有海水中溶解性无机碳浓度能充分饱和(10 ℃和20 ℃时)或接近饱和(30 ℃时)石莼的光合作用;而在气生状态下,石莼光合作用受大气CO2浓度的限制,且这种限制作用在较高温度(20-30 ℃)下比在低温(10 ℃)下更严重.在10 ℃和20 ℃时,石莼在气生状态下比在水生状态下具有更高的碳饱和最大光合速率;而在30 ℃时,石莼在这两种状态下的碳饱和光合速率相似.石莼光合作用的Km (CO2)值在气生状态下比在水生状态下高;而在气生状态下石莼对CO2的表观光合导度远小于其在水生状态下的值.认为大气CO2浓度升高将通过促进石莼在气生状态下的光合作用而增加其初级生产力.     

基于无人机的冬小麦拔节期表层土壤有机质含量遥感反演

快速监测大面积分布的盐渍化麦田土壤有机质含量,可为推进盐渍土改良和促进碳循环研究提供数据支撑。通过野外采样与获取无人机遥感影像,分别基于裸土和植被情况,采用多元线性回归(MLR)、偏最小二乘回归(PLSR)和支持向量机回归(SVR)3种方法,建立区域有机质含量遥感模型,并进行检验和对比,确定最优的土壤有机质含量反演模型;最后基于最优模型进行研究区表层土壤有机质的反演,并与插值结果进行比较。结果表明: 经5×5的中值滤波处理后的光谱与土壤表层有机质对应最优;3种模型中,SVR模型的预测精度最高,PLSR次之,MLR效果最差。对比两种变量的建模效果,基于植被的SVR建模效果最好,其建模决定系数(R²)、均方根误差(RMSE)分别为0.89、0.20,验证R²、RMSE分别为0.82、0.24;基于裸土的建模效果不理想,最优的也是SVR模型,其建模R²、RMSE分别为0.63、0.26,验证R²、RMSE分别为0.61、0.25。根据最优模型反演得到该区域有机质含量为17.51～22.53 g·kg^-1,平均值为19.51 g·kg^-1,与实地调查结果较为一致;插值结果与反演结果相比,精度受到限制。综上,基于无人机多光谱可以对盐渍土冬小麦拔节期土壤有机质含量进行快速、大范围精准估测。     

青海湖裸鲤自然产卵场的生境特征及无人机遥测判别——以泉吉河为例

自然产卵场是维持物种延续最关键的栖息地,青海湖裸鲤（Gymnocypris przewalskii）的自然繁殖栖息地状况和生境特征尚缺乏详细的定量研究。以青海湖入湖河流泉吉河为例,在平水期采用现场调查和无人机遥测的方法对青海湖裸鲤的自然产卵场分布及生境状况进行调查,确定其产卵场生境特征参数,建立基于无人机遥测识别产卵场的方法并进行复核验证。结果表明：泉吉河河道形态可分为弯曲型、分汊型和顺直型等三种典型河型,青海湖裸鲤自然产卵场主要分布在弯曲型和分汊型河道中,分汊型河道几乎100%都有产卵场分布,弯曲型河道有70%为产卵场;产卵场河道平均长度（135.13±61.13） m,平均宽度（30.01±17.51） m,平均曲折度1.09±0.07;平均面积（4586.6±4201.61） m²;产卵场常位于缓水浅滩处,平均水深（0.19±0.10） m （范围：0.03-0.44m）,平均流速（0.24±0.20） m/s （范围：0.01-0.81m/s）,河床质为含有沙粒的卵石（粒径：163-256mm）底质。河道形态、沙洲分布、水深特征等特征参数可作为无人机遥测识别产卵场的判断条件,并实现验证成功。研究结果可为开展整个流域的青海湖裸鲤自然产卵场现状评估及保护对策制定提供技术支撑。