Complex effects of mammalian grazing on extramatrical mycelial biomass in the Scandes forest‐tundra ecotone

Mycorrhizal associations are widespread in high‐latitude ecosystems and are potentially of great importance for global carbon dynamics. Although large herbivores play a key part in shaping subarctic plant communities, their impact on mycorrhizal dynamics is largely unknown. We measured extramatrical mycelial (EMM) biomass during one growing season in 16‐year‐old herbivore exclosures and unenclosed control plots (ambient), at three mountain birch forests and two shrub heath sites, in the Scandes forest‐tundra ecotone. We also used high‐throughput amplicon sequencing for taxonomic identification to investigate differences in fungal species composition. At the birch forest sites, EMM biomass was significantly higher in exclosures (1.36 ± 0.43 g C/m²) than in ambient conditions (0.66 ± 0.17 g C/m²) and was positively influenced by soil thawing degree‐days. At the shrub heath sites, there was no significant effect on EMM biomass (exclosures: 0.72 ± 0.09 g C/m²; ambient plots: 1.43 ± 0.94). However, EMM biomass was negatively related to Betula nana abundance, which was greater in exclosures, suggesting that grazing affected EMM biomass positively. We found no significant treatment effects on fungal diversity but the most abundant ectomycorrhizal lineage/cortinarius, showed a near‐significant positive effect of herbivore exclusion (p = .08), indicating that herbivory also affects fungal community composition. These results suggest that herbivory can influence fungal biomass in highly context‐dependent ways in subarctic ecosystems. Considering the importance of root‐associated fungi for ecosystem carbon balance, these findings could have far‐reaching implications.     

狐尾藻属狭域种和广布种断枝的生长与再生能力比较研究

对比研究了广布种穗花狐尾藻(Myriophyllum spicatum L.)和狭域种扬子狐尾藻(M. oguraense Mikisubsp. yangtzense Wang)不同长度(5、10 和15 cm)和不同位置(顶枝、中枝和底枝)断枝的生长和再生能力。研究结果显示, 两物种由断枝生长所形成植株的总生物量、分枝生物量、分枝数均随断枝长度的增加而增大;在由不同位置的断枝生长所形成的植株中, 顶枝所形成植株的总生物量最大, 中枝所形成植株的分枝生物量、分枝数和平均分枝长最大。由断枝所形成植株的总生物量、分枝生物量、分枝数、平均分枝长和新分枝所处位置在种间均存在显著差异, 穗花狐尾藻顶枝和中枝的生物量较大, 顶枝所产生的分枝位于断枝基部; 扬子狐尾藻的分枝生物量、分枝数及平均分枝长较大, 新产生的分枝多位于断枝顶端附近。研究结果表明穗花狐尾藻和扬子狐尾藻断枝的再生对策不同, 前者是增加对断枝总生物量的投资, 而后者是增加对断枝产生新分枝的投资。研究结果可为进一步开展水生植物广布种与狭域种的生活史对策研究提供资料, 也为湿地物种多样性保护与管理提供科学指导       

川赤芍的化学成分研究

从川赤芍Paeonia anomala subsp·veitchii根皮的70%丙酮提取物中,分离鉴定了22个化合物,其中包括一个新的24,30位降常春藤皂苷三萜衍生物,命名为paeonenolide H(1)。化合物2,4,9,10为首次从该植物中分离得到。     

Control of Culex quinquefasciatus (Diptera: Culicidae) by Bacillus sphaericus and B. thuringiensis subsp. israelensis, Produced on a New Potato Extract Culture Medium

The efficacy of Bacillus sphaericus and B. thuringiensis israelensis produced on a new potato-based culture medium as well as the conventional culture medium of Luria Bertani was compared against Culex quinquefasciatus in the field. After sporulation, the spores/crystals were harvested and used. The bacterial samples controlled the larvae and pupae for three weeks. Mortality due to the bacterial toxins produced from the new culture medium was very high and comparable to that produced using conventional medium. But the cost for cultivating these bacteria using potato extract was much lower as compared with that of the conventional medium.     

胡萝卜软腐果胶杆菌CpxP蛋白纯化及抑菌功能鉴定

胡萝卜软腐果胶杆菌是世界十大植物病原菌之一,主要侵染十字花科的经济作物和观赏花卉。文中从胡萝卜软腐果胶杆菌的基因组中克隆1个抗菌基因cpxP(GeneID:29704421),将其构建在原核表达质粒pET-15b上,并转化至大肠杆菌Escherichia coli BL21 (DE3)进行表达,经纯化后进行稳定性和抑菌实验。结果显示,IPTG的诱导终浓度为1mmol/L,实现了蛋白的高效外源表达,纯化后电泳无杂蛋白残留,且该蛋白具有良好的热稳定性和pH稳定性。CpxP蛋白抑菌试验结果显示其对胡萝卜切片的抑菌率可达到44.89%,对马铃薯切片的抑菌率可达到59.41%。为进一步解释其抑菌机理,研究该蛋白的空间结构可为软腐病的防治和新型蛋白农药靶点研究提供新思路。     

Preliminary Report of RAPD Analysis in Paeonia suffruticosa Subsp. spontanea and Paeonia rockii

Ten different oligonucleotide primers of arbitrary sequence were used in Capillary and Air Thermocycler to amplify genomic total DNA of Paeonia suffruticosa subsp. spontanea and P. rockii isolated from several local populations in Shanxi, Shaanxi and Gansu provinces. Under the strictly standardized amplification condition for all the primers, these primers yielded clear and reproducible bands corresponding to amplified products and separable by agarose gel electrophoresis. Among a total of 71 bands amplified, 16(22. 5%) were polymorphic in a single individual of P. suffruticosa subsp. spontanea, while among a total of 76 bands 21(27.6%)were polymophic in a single individual of P. rockii. On an average,the pairwise marker difference between band profiles of conspecific individuals (different populations) was 7.9 for P. suffruticosa subsp. spontanea and 8.7 for P. rockii respectively. The average marker difference between P. suffruticosa subsp. spontanea and P. rockii was 10.3. Obviously, greater number of plants and primers will be required to detect satisfactorily level of genetic diversity. These preliminary results showed that intraspecific genetic diversity was low for the two endangered species. RAPD as a molecular marker was useful and feasible for detecting the genetic variation within species of wild moutans. And it was also potential for studying evolution and relationships between species.     

sacA and nisA genes are not always linked in Lactococcus lactis subsp. lactis strains

Sixty-seven lactococcal strains arising from dairy habitat were screened for the presence of the sucrose 6-phosphate hydrolase gene by polymerase chain reaction. Of the strains tested, 35.8% were able to ferment sucrose as well as to harbour the sucrose-6-phosphate hydrolase gene, even though they were unable to produce nisin as well as to show the nisin structural gene. After pulsed-field gel electrophoresis and hybridisation all Suc⁺Nis⁻ strains exhibited physical linkage between sacA gene and the left end of lactococcal transposons (Tn5276 or Tn5301) without linkage to nisin genes. However, we were unable to transfer the sacA gene as well as to detect Suc⁻ derivatives from Suc⁺Nis⁻ strains after conjugation and curing experiments.     

建立液相芯片方法检测鉴别结核分枝杆菌复合群、鸟分枝杆菌与副结核分枝杆菌

运用液相芯片技术原理,以分枝杆菌菌种(群)特异基因序列IS6110、IS1081、IS1245和F57为目标基因,设计筛选4套扩增引物和杂交探针,建立同时检测鉴别结核分枝杆菌复合群、鸟分枝杆菌和副结核分枝杆菌的四重液相基因芯片检测方法。对13种共54株分枝杆菌菌株以及23种常见微生物样品的检测结果显示,四重液相芯片方法可特异检测鉴别目标菌种(群),与其它分枝杆菌菌种或微生物无非特异交叉反应;检测敏感性达2.1×101-2.5×102基因拷贝或0.06-0.74 fg DNA;组内检测变异系数和组间检测变异系数均<10%。采用四重液相芯片方法从临床结核疑似人痰样和牛组织样品中检出结核致病菌,检出率分别达75.6%(99/131)和94.9%(37/39),显著高于培养法(38.9%和53.8%)。对副结核疑似临床样品的检测试验结果显示,四重液相芯片方法与荧光PCR方法的阳性符合率为83%(24/29)。对四重混合模板的检测试验结果显示该液相芯片方法可鉴别不同菌种混合感染。四重液相芯片方法的检测周期<1 d,其中对纯化DNA模板的检测时间可在2-3 h内完成。     

Coexistent Mediterranean woody species as a driving factor of Phytophthora cinnamomi infectivity and survival

The long-term conservation of Mediterranean mixed oak forests is seriously threatened by the massive mortality of Quercus suber caused by the exotic pathogen Phytophthora cinnamomi. This species frequently grows in mixed forests under natural conditions, but nothing is known about how its level of disease might be altered by the diversity and identity of coexisting neighbours varying in susceptibility to the exotic pathogen. Here we analysed the individual and combined effects of Q. suber and the main coexisting tree species (Quercus canariensis and Olea europaea subsp. europaea var. sylvestris) in mixed forests of southern Spain on the production of infective and survival spores of P. cinnamomi. Through in vitro experiments, it was demonstrated that mixtures of Q. suber and Q. canariensis highly stimulated the production of P. cinnamomi zoospores in comparison with both species in monocultures. Olea europaea did not stimulate zoospore production. Under controlled conditions, the initial and final densities of inoculum in soil planted with monocultures of O. europaea and Q. canariensis did not differ. However, inoculum densities significantly decreased along the experiment in Q. suber mixtures with O. europaea and Q. canariensis. Phytophthora cinnamomi was able to infect and cause root rot symptoms on all tree species, including O. europaea var. sylvestris. We concluded that mixed stands of Q. suber and Q. canariensis are able to stimulate P. cinnamomi infectivity and survival much more than monospecific stands, and consequently under favourable conditions for root disease development, the coexistence of Q. suber and Q. canariensis might exacerbate Mediterranean forests decline. This study also constitutes the first report of O. europaea var. sylvestris as host and inductor of P. cinnamomi sporulation under controlled conditions.     

A field experiment on the use of Pistacia lentiscus L. and Scrophularia canina L. subsp. bicolor (Sibth. et Sm.) Greuter for the phytoremediation of abandoned mining areas

Abstract

A two-year study has been conducted in an abandoned Pb/Zn mining site, with the aim of investigating the feasibility of phytoremediation using two native Mediterranean plants (Pistacia lentiscus and Scrophularia bicolor) and of assessing the performance of amendments able to reduce the toxic effects of heavy metals. The amendments used were compost, chemical fertilizer, and zeolites, used singly or in combination. Depending on the amendments applied, the two species showed different mortality rates in the different plots, but all produced an increase in P. lentiscus survival, while S. bicolor survival improved only when amended with zeolite or zeolite + fertilizer. Scrophularia bicolor proved to be a more efficient accumulator than P. lentiscus, especially for Pb uptake. Pistacia lentiscus accumulated metals mostly in the roots. The effect of amendments was to generally reduce the bioavailable metal fraction, especially lead, in the plots amended with compost. Pistacia lentiscus proved to be the most suitable species for phytostabilization and environmental restoration, both for its resistance to metals and high phytomass production. The experiments demonstrate that the use of compost not only encourages this kind of revegetation in degraded areas, but is also an economical option that uses a by-product of solid municipal waste treatment.