Zum Tode von Dr. Walter Bosshard

Ohne Zusammenfassung     

Odor-active alcohols from the fungal transformation of alpha-farnesene

Submerged microbial cultures were screened for their potential to oxifunctionalize alpha-farnesene. The major oxidation product in all transforming cultures, 3,7,11-trimethyldodeca-1,3(E),5(E)10-tetraen-7-ol, showed a pleasant citrus-like odor and peak concentrations of 170 mg L-1. An Aspergillus niger isolate from mango generated another two terpene alcohols identified as diastereomeric menth-1-en-3-[2-methyl-1,3-butadienyl]-8-ol, a new natural compound with an apricot-like odor. The regiospecifity of the oxygen attack with concurrent lack of stereoselectivity suggested that the initial step of the bioconversion resembled the chemical autoxidation starting with the generation of an intermediate resonance-stabilized carbon-centered radical or carbocation.     

Color and albedo heterogeneity of Vesta from Dawn

Multispectral images (0.44 to 0.98 μm) of asteroid (4) Vesta obtained by the Dawn Framing Cameras reveal global color variations that uncover and help understand the north-south hemispherical dichotomy. The signature of deep lithologies excavated during the formation of the Rheasilvia basin on the south pole has been preserved on the surface. Color variations (band depth, spectral slope, and eucrite-diogenite abundance) clearly correlate with distinct compositional units. Vesta displays the greatest variation of geometric albedo (0.10 to 0.67) of any asteroid yet observed. Four distinct color units are recognized that chronicle processes--including impact excavation, mass wasting, and space weathering--that shaped the asteroid's surface. Vesta's color and photometric diversity are indicative of its status as a preserved, differentiated protoplanet.     

Substrate-controlled succession of marine bacterioplankton populations induced by a phytoplankton bloom

Phytoplankton blooms characterize temperate ocean margin zones in spring. We investigated the bacterioplankton response to a diatom bloom in the North Sea and observed a dynamic succession of populations at genus-level resolution. Taxonomically distinct expressions of carbohydrate-active enzymes (transporters; in particular, TonB-dependent transporters) and phosphate acquisition strategies were found, indicating that distinct populations of Bacteroidetes, Gammaproteobacteria, and Alphaproteobacteria are specialized for successive decomposition of algal-derived organic matter. Our results suggest that algal substrate availability provided a series of ecological niches in which specialized populations could bloom. This reveals how planktonic species, despite their seemingly homogeneous habitat, can evade extinction by direct competition.     

Reorganisation of the caecal extracellular matrix upon Salmonella infection--relation between bacterial invasiveness and expression of virulence genes

Interactions of Salmonella (S.) outer membrane structures with extracellular matrix (ECM) of host tissues seem to be crucial for bacterial adhesion and invasion. To evaluate the relationship between the ECM and bacterial invasiveness, the reorganisation of fibronectin, tenascin-C and laminin after Salmonella exposure in vivo, the Salmonella adhesiveness to ECM proteins in vitro and the virulence gene expression upon co-cultivation of salmonellae and ECM proteins were elucidated for two Salmonella strains with different capabilities to enter the intestinal mucosa. Immunohistochemistry and confocal microscopy showed that the infection of day-old chicks using either the highly invasive S. Enteritidis (SE) or the nearly non-invasive S. Infantis (SINF) strain was associated with an invasion-dependent reorganisation of fibronectin and tenascin-C in the caecal wall. Compared to SINF, clustered formations of SE were localised within and attached to the fibronectin and tenascin-C scaffold in the lamina propria indicating a relevance of ECM for bacterial dissemination in lower regions of the mucosa. In adhesion assays, SE was, indeed, significantly more adhesive to the matrix proteins than SINF. The attachment was accompanied by an increased fliC mRNA expression in SE demonstrated by microarray analysis as well as quantitative real-time RT-PCR. The data suggest a relationship between the capability of Salmonella serovars to interact with matrix proteins and to disseminate in gut mucosa perhaps in consequence of a matrix-mediated upregulation of the Salmonella motility gene fliC.     

Effects of perennial fodder crops on soil structure in agricultural headlands

In agricultural headlands, rooting and yield of crops may be limited because of soil‐structure changes as a consequence of multiple passes of turning machinery. We hypothesized that perennial forage crops can substantially alter soil structure in agricultural headlands. On one experimental field and two commercial farms on Haplic Luvisols from respectively loess and sandy loess in the Lower Rhine Bay (Germany), we investigated how 4 y of continuously grown grass/clover or alfalfa affected soil structure and the performance of subsequent spring wheat. Compared with a crop rotation with annual plowing to 30 cm soil depth, perennial forage crops led to increased soil C content (+1.3% to +22.8%) and N content (+4.2% to +15.1%), higher densities of medium and coarse biopores at a depth of 35 cm, more large water‐stable soil macroaggregates, higher biomass and abundance of anecic earthworms, and higher grain yield and grain protein content of spring wheat grown as the following crop. Root‐length density of spring wheat in the subsoil was not affected by the preceding perennial fodder crops in two of the three field trials. We concluded that besides increasing N input to the soil, perennial cropping of grass/clover or alfalfa has effects on soil structure that may substantially reduce yield losses in agricultural headlands.     

Molecular characterization, ecology, and epidemiology of a novel Tymovirus in Asclepias viridis from Oklahoma

Native virus-plant interactions require more understanding and their study will provide a basis from which to identify potential sources of emerging destructive viruses in crops. A novel tymovirus sequence was detected in Asclepias viridis (green milkweed), a perennial growing in a natural setting in the Tallgrass Prairie Preserve (TGPP) of Oklahoma. It was abundant within and frequent among A. viridis plants and, to varying extents, within other dicotyledonous and one grass (Panicum virgatum) species obtained from the TGPP. Extracts from A. viridis containing the sequence were infectious to a limited number of species. The virus genome was cloned and determined to be closely related to Kennedya yellow mosaic virus. The persistence of the virus within the Oklahoma A. viridis population was monitored for five successive years. Virus was present in a high percentage of plants within representative areas of the TGPP in all years and was spreading to additional plants. Virus was present in regions adjacent to the TGPP but not in plants sampled from central and south-central Oklahoma. Virus was present in the underground caudex of the plant during the winter, suggesting overwintering in this tissue. The RNA sequence encoding the virus coat protein varied considerably between individual plants (≈3%), likely due to drift rather than selection. An infectious clone was constructed and the virus was named Asclepias asymptomatic virus (AsAV) due to the absence of obvious symptoms on A. viridis.     

Investigations concerning the prevalence of Coxiella burnetii and Chlamydia abortus in sheep in correlation with management systems and abortion rate in Lower Saxony in 2004

The intracellular bacteria Coxiella (C) burnetii and Chlamydia (Chl) abortus induce abortion in sheep and also affect humans. While Chl. abortus only infrequently infects humans, C burnetii is the aetiological agent of numerous Q fever outbreaks during the last decades. There is only limited knowledge about the prevalence of both pathogens in sheep, although sheep are involved in almost all Q fever outbreaks in Germany. The aim of our study was to investigate the prevalence of both pathogens in flocks located in Lower Saxony, Germany, in correlation to the management form and abortion rate. Serum samples of 1714 sheep from 95 flocks located in Lower Saxony were investigated by ELISA. 2.7% of these samples were positive, 1.3% showed inconclusive results in the C. burnetii-ELISA. Elevated intra-flock seroprevalences were only detected in three migrating flocks. Chlamydia-specific antibodies could be detected in 15.1% serum samples of mainly shepherded and migrating flocks. In one of these flocks with a high intra-flock seroprevalence for C burnetii (27%) and Chlamydia (44.9%), C burnetii was detected in 21.6% of the placenta samples of normal births and in 12.5% of the colostrum samples by PCR. Aborted fetuses and the corresponding placentas were negative in C burnetii-PCR, but in most of them and also in many other placenta samples Chl. abortus could be detected by PCR and DNA microarray. This survey shows a low overall prevalence of C. burnetii in sheep in Lower Saxony in the year 2004. However, three migrating flocks with a high intra-flock prevalence are localized in the southern parts of Lower Saxony. Spreading of C burnetii could occur, because of the large radius of grazing of all three flocks.     

Response of maize (Zea mays) inbreds and hybrids to rimsulfuron

Abstract: Extensive glasshouse studies characterized the varietal response to rimsulfuron of 37 inbreds of maize (Zea mays L.), representing the major inbred families used in hybrid seed production, and 20 defined hybrids from these inbreds. Tolerant hybrids were produced when one or both of its parents were tolerant. Sensitive hybrids occurred only when both parents were sensitive. Genetic analysis indicated that sensitivity is controlled by a single recessive gene. Dose-response analysis showed varieties could vary more than 40000-fold in sensitivity. Only the AHAS-modified variety with the XA-17 gene had changed enzyme sensitivity. This gene provided crop tolerance to very high rates of rimsulfuron and its interaction with an organophosphate insecticide. Breeders can eliminate varietal sensitivity in three ways: always use at least one tolerant hybrid parent, backcross sensitive inbreds with tolerant, or use an AHAS-modified gene.