芳香植物精油对竹子根际微生物种群的影响

竹林生态系统虽然比较稳定,但病原菌也较多,使用生物农药是竹林可持续发展的必然道路。许多芳香植物精油具有优良的抗菌活性,都有作为生物农药的潜力。但是竹林土壤微生物也可能受到精油抑菌性能的影响。本研究选取常见5种芳香植物精油香茅、肉桂、大蒜、生姜和茶树精油,对其化学成分进行鉴定并对毛竹实生盆栽苗的土壤进行处理,测定毛竹根际土壤微生物的细菌丰度和种群多样性。结果表明,5种精油会降低毛竹根际微生物的丰度和多样性,使变形菌门的细菌成为绝对优势菌群。对微生物的影响从大到小依次是香茅、生姜、茶树、肉桂和大蒜精油。     

Aluminium precipitates from groundwater of an aquifer affected by acid atmospheric deposition in the Senne,Northern Germany

White precipitates collected from stream bottoms and well tubes in the Senne area consist of amorphous aluminium hydroxide, coprecipitated with minor amounts of sulfate, phosphate and silica. The precipitates have presumably formed by the interaction of slightly alkaline water from calcareous subsoil sediments, with acidic water draining off sandy soils affected by high inputs of acidic atmospheric deposition. From many hydrochemical studies, precipitation of aqueous aluminium is known to occur in subsurface horizons of acid soils affected by acid rain. On the basis of presumed equilibrium with soil solutions, jurbanite, AlOHSO₄ · 5H₂O, is often assumed to be the secondary mineral involved. However, direct evidence for jurbanite from solid phase analysis is lacking. This first analysis of such a secondary phase does not support the jurbanite hypothesis, and shows that amorphous Al hydroxide can be formed instead.     

Nano-scale secondary ion mass spectrometry — A new analytical tool in biogeochemistry and soil ecology: A review article

Soils are structurally heterogeneous across a wide range of spatio-temporal scales. Consequently, external environmental conditions do not have a uniform effect throughout the soil, resulting in a large diversity of micro-habitats. It has been suggested that soil function can be studied without explicit consideration of such fine detail, but recent research has indicated that the micro-scale distribution of organisms may be of importance for a mechanistic understanding of many soil functions. Current techniques still lack the adequate sensitivity and resolution for data collection at the micro-scale, and the question ‘How important are various soil processes acting at different scales for ecological function?’ is therefore challenging to answer. The nano-scale secondary ion mass spectrometer (NanoSIMS) represents the latest generation of ion microprobes, which link high-resolution microscopy with isotopic analysis. The main advantage of NanoSIMS over other secondary ion mass spectrometers is its ability to operate at high mass resolution, whilst maintaining both excellent signal transmission and spatial resolution (down to 50 nm). NanoSIMS has been used previously in studies focussing on presolar materials from meteorites, in material science, biology, geology and mineralogy. Recently, the potential of NanoSIMS as a new tool in the study of biophysical interfaces in soils has been demonstrated. This paper describes the principles of NanoSIMS and discusses the potential of this tool to contribute to the field of biogeochemistry and soil ecology. Practical considerations (sample size and preparation, simultaneous collection of isotopes, mass resolution, isobaric interference and quantification of the isotopes of interest) are discussed. Adequate sample preparation, avoiding bias due to artefacts, and identification of regions-of-interest will be critical concerns if NanoSIMS is used as a new tool in biogeochemistry and soil ecology. Finally, we review the areas of research most likely to benefit from the high spatial and high mass resolution attainable with this new approach.     

Pathologic and immunohistochemical findings in an outbreak of systemic toxoplasmosis in a mob of red kangaroos

Toxoplasma gondii is a zoonotic protozoan pathogen that infects many endothermic vertebrates, including humans; the domestic cat and other felids serve as the definitive host. Macropodids are considered highly susceptible to toxoplasmosis. Here, we describe the clinical, pathologic, and immunohistochemical findings of an outbreak of systemic toxoplasmosis in a mob of 11 red kangaroos (Macropus rufus), with high morbidity (73%) and mortality (100%) rates. Affected animals had either severe and rapidly deteriorating clinical conditions or sudden death, which was correlated with widespread necrotizing lesions in multiple organs and intralesional T. gondii organisms identified via MIC3-specific immunohistochemistry and confirmed by REP529-specific rtPCR. Quantification of parasites demonstrated the highest parasite density in pulmonary parenchyma compared with other tissues. Our study highlights the continued importance of this severe condition in Australian marsupials.     

Structure of PTB bound to RNA: specific binding and implications for splicing regulation

The polypyrimidine tract binding protein (PTB) is a 58-kilodalton RNA binding protein involved in multiple aspects of messenger RNA metabolism, including the repression of alternative exons. We have determined the solution structures of the four RNA binding domains (RBDs) of PTB, each bound to a CUCUCU oligonucleotide. Each RBD binds RNA with a different binding specificity. RBD3 and RBD4 interact, resulting in an antiparallel orientation of their bound RNAs. Thus, PTB will induce RNA looping when bound to two separated pyrimidine tracts within the same RNA. This leads to structural models for how PTB functions as an alternative-splicing repressor.     

Different reactions of central and marginal provenances of Fagus sylvatica to experimental drought

Climate extremes are expected to increase in frequency and magnitude as a consequence of global warming, threatening the functioning, services and goods of forest ecosystems. Across Europe, the ecologically and economically important tree species Fagus sylvatica is expected to suffer particularly under such conditions. The regional introduction of provenances from drier and warmer climates is one option to adapt beech forest ecosystems to these adverse effects of climate change. Marginal populations from the drought-prone southern and north-eastern edges of the species’ distribution come into focus in search of suitable candidates for Central European deciduous forests. Here, we test three marginal provenances (Spain, Bulgaria and Poland) and three provenances from the centre of the distribution range (Germany) for their response to drought in two different soil types (sand, loam) in a full factorial common garden experiment in Landau, Germany. Drought impacted all growth parameters negatively (leaf damage +22 % (percentage points), height ?40 % and diameter increment ?41 %), and the sandy substrate exacerbated this effect. However, provenances differed in their response to drought and soil type. Evidence for a local adaptation to summer drought was detected, especially in terms of mortality rates. The Bulgarian and Spanish provenance showed a stable performance under drought conditions (BG ?27 % in diameter increment; ES ?32 %), compared to the Polish (?48 %) or the most sensitive German provenances (?57 %), yet for Bulgaria on a low level of total increment. This may indicate a trade-off between drought tolerance and growth. Therefore, a sole focus on drought-resistant marginal provenances seems to not be conducive, as they might be less adapted to other climatic factors, e.g. frost, as well. However, intermixed with local Central European provenances, these may act as functional insurance in future drought-prone forest stands.     

A process for controlling intracellular bacterial infections induced by membrane injury

Strategies for inhibiting phagolysosome fusion are essential for the intracellular survival and replication of many pathogens. We found that the lysosomal synaptotagmin Syt VII is required for a mechanism that promotes phagolysosomal fusion and limits the intracellular growth of pathogenic bacteria. Syt VII was required for a form of Ca2+-dependent phagolysosome fusion that is analogous to Ca2+-regulated exocytosis of lysosomes, which can be triggered by membrane injury. Bacterial type III secretion systems, which permeabilize membranes and cause Ca2+ influx in mammalian cells, promote lysosomal exocytosis and inhibit intracellular survival in Syt VII +/+ but not -/- cells. Thus, the lysosomal repair response can also protect cells against pathogens that trigger membrane permeabilization.