Rapid changes in the rhizosphere bacterial community structure during re-colonization of sterilized soil

Diversity has been shown to be pivotal in ecosystem stability and resilience. It is therefore important to increase our knowledge about the development of diversity. The aim of this study was to investigate the temporal dynamics of the bacterial community structure in the rhizosphere of wheat plants growing in a soil in which the initial conditions for bacterial re-colonization were modified by mixing different amounts of sterilized with native soil at ratios of 19:1, 9:1, 4:1 and 1:1. Additional treatments comprised sterilized soil or native soil. Plant dry weight at day 20 decreased with increasing percentage of native soil in the mix. The bacterial community structure in the rhizosphere was assessed by polymerase chain reaction-denaturing gradient gel electrophoresis (DGGE) at days 3, 14 and 20 after planting. The bacterial community in the sterilized soil had a lower diversity and evenness than the native soil. Both diversity and evenness increased with time in the sterilized soil. Community structure in the different mixes changed over time and the changes were mix-specific. Principal component analyses of the DGGE banding patterns showed clear differences between the treatments particularly at day 3 and day 14 and revealed changes in community structure within a few days in a given treatment. The results of the present study show that bacterial communities rapidly re-colonize sterilized soil. During re-colonization, the community structure changes rapidly with a general trend towards higher diversity and evenness. The changes in community structure over time are also affected by the amount of sterile substrate to be re-colonized.     

Effect of technological processing on the allergenicity of mangoes (Mangifera indica L.)

In parallel with the rising popularity of exotic fruits in Europe, allergy against mango is of increasing importance. Because mangoes are also consumed as processed products such as chutneys or beverages, the influences of different process conditions on their allergenicity were investigated. Mango purees and nectars were manufactured at small pilot-plant scale, and the allergenic potencies of the resulting intermediate and final products were determined by means of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting and inhibitive enzyme allergosorbent tests (EAST-inhibition), using a pool serum of 9 individuals with manifest mango allergy. The mango allergens were shown to be very stable during technological processing. Irrespective of enzymatic matrix decomposition, mechanical tissue disintegration and heating during peeling, mash treatment, and pasteurization, significant loss of allergenicity could not be observed in the extracts of mango purees and nectars derived thereof. These results were confirmed by analogous investigation of commercial mango drinks and nectars. Hence, conventional mango processing into pulp-containing products typical for this species obviously does not allow complete elimination of the allergenic potency.     

肾形肾状线虫（Rotylenchulus reniformis）浙江杭州 群体形态学和分子特性及寄主范围

 肾形肾状线虫（Rotylenchulus reniformis）是一种重要的蔬菜线虫,寄主范围和分布很广。本文根据形态学特征和形态测量将来自浙江省杭州市蔬菜上的肾状线虫群体鉴定为肾形肾状线虫,为浙江省首次报道。该群体的形态学特征及形态测量值与模式标本基本吻合,个别形态测量值(比值)有变异。通过对该肾形肾状线虫群体的rDNA中ITS区和编码28S RNA基因中的D2D3区的PCR扩增和序列测定,明确二序列长度分别为808 bp和786 bp;序列分析发现该群体ITS序列与肾形肾状线虫种内一些两性生殖群体的亲缘关系较近,同源性高达99.5%～100%,而与一孤雌生殖群体同源性为92.4%;编码28S RNA基因中的D2D3区与已报道群体的同源性达到99.4%,相似度较高;本研究还发现杭州肾形肾状线虫群体的寄主涉及11个科16个属的果蔬。     

Enhanced glucosinolates in root exudates of Brassica rapa ssp. rapa mediated by salicylic acid and methyl jasmonate

Elicitation studies with salicylic acid (SA) and methyl jasmonate (MJ) inducing a targeted rhizosecretion of high levels of anticarcinogenic glucosinolates in Brassica rapa ssp. rapa plants were conducted. Elicitor applications not only led to an accumulation of individual indole glucosinolates and the aromatic 2-phenylethyl glucosinolate in the turnip organs but also in turnip root exudates. This indicates an extended systemic response, which comprises the phyllosphere with all aboveground plant organs and the rhizosphere including the belowground root system and also root exudates. Both elicitor applications induced a doubling in 2-phenylethyl glucosinolate in root exudates, whereas application of MJ enhanced rhizosecreted indole glucosinolates up to 4-fold. In addition, the time course study revealed that maximal elicitation was observed on the 10th day of SA and MJ treatment. This study may provide an essential contribution using these glucosinolates as bioactive additives in functional foods and nutraceuticals.     

Natural product terpenoids in Eocene and Miocene conifer fossils

Numerous saturated and aromatic hydrocarbons, but not polar compounds, originating from plants and microorganisms (biomarkers) have been reported in sediments, coals, and petroleum. Here we describe natural product terpenoids found in two fossil conifers, Taxodium balticum (Eocene) and Glyptostrobus oregonensis (Miocene). A similar terpenoid pattern is also observed in extant Taxodium distichum. The preservation of characteristic terpenoids (unaltered natural products) in the fossil conifers supports their systematic assignment to the Cypress family (Cupressaceae sensu lato). The results also show that fossil conifers can contain polar terpenoids, which are valuable markers for (paleo)chemosystematics and phylogeny.     

Field and laboratory investigations of Lumbricus badensis ecology and behaviour

正Dear Editor,Deep burrowing and soil surface feeding earthworms,so-called strict-anecic and epi-anecic species (Hoeffner et al., 2019), are a highly influential soil faunal group in many natural and manmade environments. Typically, they are relatively large and contribute substantially to the formation and processes of mull-type soils through effective foraging and incorporation of plant litter (Edwards and Bohlen,     

Density fractionation of organic matter in dolomite‐derived soils

Dolomite (CaMg(CO₃)₂) constitutes half of the global carbonates. Thus, many calcareous soils have been developing rather from dolomitic rocks than from calcite (CaCO₃)‐dominated limestone. We developed a physical fractionation procedure based on three fractionation steps, using sonication with subsequent density fractionation to separate soil organic matter (SOM) from dolomite‐derived soil constituents. The method avoids acidic pretreatment for destruction of carbonates but aims at separating out carbonate minerals according to density. The fractionation was tested on three soils developed on dolostone parent material (alluvial gravel and solid rock), differing in organic‐C (OC) and inorganic‐C (IC) concentrations and degree of carbonate weathering. Soil samples were suspended and centrifuged in Na‐polytungstate (SPT) solutions of increasing density, resulting in five different fractions: two light fractions < 1.8 g cm^–3 (> 20 μm and < 20 μm), rich in OC and free of carbonate, and two organomineral fractions (1.8–2.4 g cm^–3 and 2.4–2.6 g cm^–3), containing 66–145 mg g^–1 and 16–29 mg g^–1 OC. The organomineral fractions consist of residual clay from carbonate weathering such as clay minerals and iron oxides associated with SOM. The fifth fraction (> 2.6 g cm^–3) was dominated by dolomite (85%–95%). The density separation yielded fractions differing in mineral compositions, as well as in SOM, indicated by soil‐type‐specific OC distributions and decreasing OC : N ratios with increasing density of fractions. The presented method is applicable to a wide range of dolomitic and most likely to all other calcareous soils.     

Reduction of in vitro growth in Flavobacterium columnare and Saprolegnia parasitica by products containing peracetic acid

Commercial products containing peracetic acid (PAA) are strong disinfectants with a wide spectrum of antimicrobial activity and have been suggested as potential therapeutic agents in aquaculture. The aim of this study was to compare the in vitro reduction of growth on two fish pathogens, Flavobacterium columnare and Saprolegnia parasitica, by seven commercial PAA‐containing products. Flavobacterium columnare was exposed to 1, 2, 4, 6, 8 and 10 mg L^?1 PAA and S. parasitica was exposed to 0.5, 1, 2, 4, 6, 8 and 10 mg L^?1 PAA in petri dishes for 24 h incubation. The reduction of growth was measured in comparison to a PAA‐free control. A reduction of the growth was observed for both pathogens with increasing PAA concentration. Hydrogen peroxide (H₂O₂) possibly has a role in the effectiveness of the products, since products with lower PAA concentrations had a higher concentration of H₂O₂. The commercial products with a low concentration of PAA and a low PAA:H₂O₂‐ratio were generally more effective against pathogens. The practical application of the products with low PAA concentration should be prioritized.     

A case of a canine pigmented plaque associated with the presence of a Chi-papillomavirus

The seven fully described canine papillomaviruses (CPVs) have been allocated by sequence comparison and other genetic features into three phylogenetic clades. This largely reflects clinical findings, so each sequence of a newly discovered CPV in combination with clinical and pathological details is a valuable piece of evidence. We hypothesize that the genomic sequence of a new CPV can help to predict clinical features and progression, and that this can be tested in subsequent cases. In this case, a 2-year-old female dachshund-mix presented with papillomatosis clinically and histologically characterized as pigmented viral plaques. PCRs using primers evaluated for CPVs successfully amplified papillomavirus (PV) DNA. Sequencing of the products revealed an unknown PV putatively belonging to the PV genus Chi. Rolling circle amplification was used to amplify the entire viral genome. Sequencing revealed a novel PV, designated as CPV8, which was most closely related (63% homology) to the recently discovered CPV4. CPV4 is associated with benign pigmented plaques in pugs. Phylogenetic analysis based on the nucleotide sequences of four viral genes showed that the novel virus was closest to CPV3, CPV4 and CPV5. The presence of viral DNA was confirmed in the lesions by in situ hybridization using specific probes. CPV8 may consequently be regarded as the fourth member of the Chi-papillomavirus genus. All viruses belonging to this genus induce pigmented plaques in dogs. These findings support the hypothesis that genomic sequences can be useful in predicting the clinical features of CPV infection.