In vitro antimicrobial activity of different accessions ofSolanum commersonii Dun. from Uruguay

Summary The in vitro antimicrobial activity of extracts from accessions ofSolanum commersonii Dun. collected in the south of Uruguay was investigated against five microorganisms including the pathogenRalstonia solanacearum. A total of 30 extracts corresponding to organic and aqueous extracts were studied. Interestingly, most of the positive results for growth inhibition were againstR. solanacearum. The extracts were also analyzed for the presence of glycoalkaloids and lectins. Six of the ten aqueous extracts showed lectin presence and a wide variation in the type and amounts of glycoalkaloids, was found. Results indicate that there is no clear relationship between the antimicrobial activity against the five microorganisms screened and the presence or amounts of lectins and glycoalkaloids, traditionally regarded as possible antimicrobial metabolites in theSolanum genus, which indicates the presence of as yet unidentified antimicrobial compounds.     

芒果蒂腐病病原葡萄座腔菌科真菌种类鉴定

In order to identify the pathogen of Botryosphaeriaceae causing mango stem-end rot, tissue isolation method was used to process mango samples collected from Hainan, Guangxi, Yunnan, and Sichuan Provinces in China, and 58 fungal isolates were obtained. Among them, 39 isolates were belonged to Botryosphaeriaceae, accounting for 67.24%. These isolates were identified based on morphological characteristics and phylogenetic analysis with internal transcribed spacer (ITS) and elongation factor 1 alpha (EF-1α). The results showed that there were four main species of Botryosphaeriaceae, including Neofusicoccum parvum (33.33%), Lasiodiplodia theobromae (30.77%), Botryosphaeria dothidea (28.21%), and L. pseudotheobromae (7.69%). The mango stem-end rot caused by L. pseudotheobroma was firstly reported in China. The virulence of the four species was tested by in vitro inoculation and the results showed that all isolates were pathogenic, among which L. theobromae, L. pseudotheobroma, and N. parvum were the “strong” grade, and B. dothidea was the “middle” grade.     

肺炎克雷伯氏菌(Klebsiella pneumoniae)对植物影响的研究进展

 肺炎克雷伯氏菌(Klebsiella pneumoniae)不仅是重要的人和动物的条件致病菌和食源性致病菌,也是一种能够跨界侵染植物的病原菌。K. pneumoniae能够以植物作为回到人和动物寄主的载体,在植物的附生或内生生长是其生命周期的重要组成部分。它还能够跨越生物界直接侵染玉米、香蕉、石榴、高粱等,引起植物病害。在不同环境中生存的生态适应性是K. pneumoniae跨界侵染的机制。K. pneumoniae很可能利用与感染动物相同或不同的策略来侵染植物,但其机制有待进一步研究。本文综述了K. pneumoniae对植物影响的研究进展,重点介绍了其对植物的致病性,并对其众多的生态位进行了讨论。     

Identification,pathogenicity and community dynamics of fungi and oomycetes associated with pea root rot in northern France

The pea root rot complex is a major concern for green pea production worldwide. This study aimed at characterizing its composition and dynamics throughout a cropping season in northern France. To this end, fungi and oomycetes were isolated from green pea plant roots with symptoms sampled at the flowering stage in 22 fields in 2017, and at the pea emergence, elongation and flowering stages in two fields in 2018. Out of 646 isolates collected, 317 were identified using molecular markers. Fusarium oxysporum, F. solani and F. redolens were highly predominant. Pathogenicity tests separated the isolates into four aggressiveness groups. F. solani isolates were the most aggressive. Phylogenetic analysis of their TEF1 sequences showed that they mainly belonged to the F. pisi lineage, and that F. oxysporum isolates were genetically close to isolates from the UK that did not belong to the forma specialis pisi. In addition, several Clonostachys rhizophaga isolates are reported for the first time to cause pea root rot. The oomycetes were rarely found and were represented by a few Pythium spp. isolates. Lastly, this study shows that the fungal and oomycete communities associated with pea root rot change during the cropping season. The level of dissimilarity of the root-rot-associated communities decreased throughout the cropping season towards a more similar composition at the flowering stage, dominated by F. solani, F. oxysporum and F. redolens. The proportion of nonpathogenic to weakly pathogenic isolates decreased progressively during the growing season in favour of moderately to highly pathogenic isolates.     

GDF9和FST调控猪卵母细胞成熟和胚胎早期发育

为探讨生长分化因子9(Growth differentiation factor 9,GDF9)和卵泡抑素(Follistatin,FST)如何影响猪卵母细胞成熟及胚胎早期发育能力,在猪卵母细胞体外成熟(IVM)培养过程中添加不同浓度的GDF9和抗GDF9抗体,或同时添加GDF9和FST或抗FST抗体,测定猪卵母细胞的细胞核成熟率、卵裂率、囊胚率及囊胚总细胞数。结果显示,添加GDF9显著提高孤雌胚囊胚率,抗GDF9抗体则显著抑制卵裂率和囊胚率。添加FST显著降低孤雌胚囊胚率和囊胚总细胞数,添加抗FST抗体显著提高了囊胚率。共同添加GDF9与抗FST抗体则使囊胚率达到最高。表明猪卵母细胞IVM期添加GDF9能一定程度上提高卵母细胞及胚胎的发育能力,共同添加GDF9和抗FST抗体对胚胎发育的促进作用具有加性效应。     

东南地区猪圆环病毒2型检测及分子流行病学分析

【目的】分析我国东南地区2012－2018年规模化猪场猪圆环病毒2型（PCV2）的流行动态、基因组特性及病毒重组情况,为猪圆环病毒相关疾病（PCVAD）的防控和疫苗开发提供理论依据。【方法】对2012-2018年采自福建、江西、广东、江苏及浙江等省规模化猪场疑似断奶仔猪多系统衰弱综合症（PMWS）猪只的649份组织样本及血清样本采用PCR方法进行检测,对PCV2进行基因分型,并选取54份阳性样品进行PCV2全基因组同源性比对、系统发育分析和重组分析,同时对ORF2基因进行遗传进化分析和衣壳（Cap）蛋白氨基酸序列比对。【结果】东南地区猪场感染PCV2较普遍,PCV2阳性率为41.9%（272/649）。猪场存在PCV2a、PCV2b、PCV2d和PCV2e 4个基因型毒株,其中以PCV2d流行为主。基于PCV2全长核苷酸序列和ORF2基因的系统进化分析表明,54株PCV2毒株均分为4个基因型; PCV2e毒株检出率较低（仅为0.46%）,其基因组全长1 777 bp,与其他基因型代表毒株的全长核苷酸同源性较低（91.0%~93.0%）。重组分析表明,不同基因型毒株间存在重组现象。Cap蛋白的氨基酸序列分析表明,不同基因型具有特征性的突变位点。【结论】东南地区猪场存在4种基因型PCV2,其中PCV2d为优势基因型,不同基因型毒株间存在重组现象。新基因型PCV2e的检出率较低。     

Timing and temperature thresholds of heat stress effects on fertility performance of different parity sows in Spanish herds

High temperature is an environmental factor that impairs sow fertility. In this study, we identified the critical weeks for heat stress effects on aspects of fertility performance, namely weaning-to-first-service interval (WSI) and farrowing rate (FR). We also examined the threshold temperatures above which the fertility performance deteriorated and whether there were any differences between parities regarding heat stress effects or thresholds. Performance data of sows in 142 herds from 2011 to 2016 were matched to appropriate weekly averaged daily maximum temperatures (T_max) from weather stations close to the herds. Two types of ratios (i.e., ratio for WSI and odds ratio for FR) were used to identify the critical weeks for heat stress by comparing the respective measures for two sow groups based on T_max in different weeks around weaning or service events. The ratios for WSI were calculated between groups of sows exposed to T_max ≥ 27 °C or <27 °C in each week before weaning, with the T_max cutoff value based on a recent review study. Similarly, the odds ratios for FR for the two groups were calculated in weeks around service. The weeks with the largest differences in the fertility measures between the two T_max groups (i.e., the highest ratio for WSI and the lowest odds ratio for FR) were considered to be the critical weeks for heat stress. Also, piecewise models with different breakpoints were constructed to identify the threshold T_max in the critical week. The breakpoint in the best-fit model was considered to be the threshold T_max. The highest ratios for WSI were obtained at 1 to 3 wk before weaning in parity 1 and 2 or higher sow groups. The threshold T_max leading to prolonged WSI was 17 °C for parity 1 sows and 25 °C for parity 2 or higher sows. Increasing T_max by 10 °C above these thresholds increased WSI by 0.65, and 0.33 to 0.35 d, respectively (P < 0.01). For FR, the lowest odds ratios were obtained at 2 to 3 wk before service in parity 0, 1, and 2 or higher sow groups. The threshold T_max leading to reductions in FR was 20, 21, and 24 to 25 °C for parity 0, 1, and 2 or higher sow groups, respectively. Increasing T_max by 10 °C above these thresholds decreased FR by 3.0%, 4.3%, and 1.9% to 2.8%, respectively (P < 0.01). These results indicate that the critical weeks for heat stress were 2 to 3 wk before service for FR and 1 to 3 wk before weaning for WSI. The decreases in fertility performance in parity 0 to 1 sows started at temperatures 3 to 8 °C lower than in parity 2 or higher sows.     

不同温度处理对新鲜生菜上大肠杆菌生长的影响

为研究不同温度条件下恒定温度和供应链波动温度及振荡温度对细菌生长的影响提供参考依据,采用新鲜生菜叶为培养基质,以大肠杆菌K12品系中的大肠杆菌Escherichia coli 1.1187为研究对象,从恒定温度、(4、13、21、29、37℃)、振荡温度(4~37℃、37~4℃)及供应链波动温度几个因素研究其对生菜中接种大肠杆菌Escherichia coli 1.1187生长的影响。结果表明,恒定温度条件培养下,低温抑制大肠杆菌1.1187的生长,高温有利于大肠杆菌的生长繁殖。在波动温度条件培养下,大肠杆菌1.1187的生长随温度的波动而波动,在振荡温度培养下,控制初始在低温条件下可以有效地抑制大肠杆菌的生长。     

爬山虎水提液与抗菌药联用对含fosA3基因大肠杆菌的抑菌效果

[目的]探讨爬山虎水提液与抗菌药联用对含fosA3基因大肠杆菌的抑菌效果,为爬山虎的综合开发利用提供参考依据.[方法]从病猪的肠道组织分泌物中分离菌株,对其进行鉴定和fosA3基因检测,采用二倍微量稀释法检测爬山虎水提液与不同抗菌药的最小抑菌浓度(MIC),然后用微量棋盘稀释法测定爬山虎水提液与抗菌药联用的抑菌浓度指数(FICI).[结果]分离获得的菌株为含fosA3基因大肠杆菌,爬山虎水提液对含fosA3大肠杆菌的MIC为500g/mL.以500 g/mL爬山虎水提液与头孢曲松钠、磷霉素、粘杆菌素、痢菌净、磺胺间甲氧嘧啶、阿米卡星、头孢噻呋钠、氟苯尼考、头孢噻肟等9种抗菌药联用的FICI为0.188～1.000,其中,爬山虎水提液与粘杆菌素、氟苯尼考间存在协同作用,与头孢曲松钠、磷霉素、痢菌净、磺胺间甲氧嘧啶、阿米卡星、头孢噻呋钠、头孢噻肟呈相加作用.[结论]爬山虎水提液可增强部分抗菌药对含fosA3大肠杆菌的抗菌活性,且呈协同或相加作用.     

热纤维素梭菌内切葡聚糖苷酶基因在枯草芽孢杆菌的表达

对热纤维素梭菌Clostridium thermocellum内切葡聚糖苷酶基因CelG及其信号肽序列进行了克隆及表达研究.以热纤维素梭菌总DNA为模板,经PCR扩增获得目的,并连接到大肠杆菌-枯草杆菌穿梭质粒pSW1载体,获得质粒pSW1-CelG;用感受态转化法将获得质粒pSW1-CelG转化到枯草芽孢杆菌BGSC中进行分泌表达,获得了大小约56KD的蛋白片段,且具有生物活性,证明CelG基因克隆成功并正确表达.