Characterization of Picea abies (L.) Karst. ectomycorrhizas: discrepancy between classification according to macroscopic versus microscopic features

Summary In a 3-year study of ectomycorrhizal diversity in 2 Norway spruce stands in Switzerland the macroscopically classified ectomycorrhizal types were analyzed microscopically to compare the results of the 2 approaches. A total of 22 ectomycorrhizal types were macroscopically classified in the 2 stands. Microscopic investigations — particularly of mantle structures — resulted in the identification of 7 additional types to give a total of 29. These additional types resulted from separation of macroscopically identical types occurring on both stands (type-pairs) at the microscopic level. The problematic nature of characterization and classification of ectomycorrhizas is discussed.     

The process utility of thermotolerant methylotrophic bacteria: I. An evaluation in chemostat culture

In Part l, the process utility of a thermotolerant methylotrophic bacterium is evaluated in chemostat culture under conditions where methanol, methanol/formaldehyde mixtures and dual methanol/ammonia limitation occurred. The results show that the bacterium studied was nonfastideous under steady-state operation, in contrast to results obtained in batch culture. For application in industrial wastewater treatment processes the bacterium should be employed in systems where the biomass residence time exceeds 5 h, i. e., dilution rates < O.2 h(-1). Under such conditions, methanol was essentially exhausted and the biomass yield coefficient was lowered.     

Regulation of the synthesis of methanol oxidizing enzymes inKloeckera sp. 2201 andHansenula polymorpha,a comparison

A comparative study was made of the regulation of the synthesis of methanol dissimilating enzymes inkloeckera sp. 2201 andHansenula polymorpha using chemostat and batch growth conditions and methanol or glucose as carbon sources. During growth in methanol-limited chemostat cultures similar enzyme patterns for alcohol oxidase, catalase, formaldehyde dehydrogenase and formate dehydrogenase in the two yeasts were found. When growing in batch culture with glucoseH. polymorpha, but notKloeckera sp. 2201, was found to produce ethanol which might affect the synthesis of these enzymes.     

Model-based inference of neutralizing antibody avidities against influenza virus

To assess the response to vaccination, quantity (concentration) and quality (avidity) of neutralizing antibodies are the most important parameters. Specifically, an increase in avidity indicates germinal center formation, which is required for establishing long-term protection. For influenza, the classical hemagglutination inhibition (HI) assay, however, quantifies a combination of both, and to separately determine avidity requires high experimental effort. We developed from first principles a biophysical model of hemagglutination inhibition to infer IgG antibody avidities from measured HI titers and IgG concentrations. The model accurately describes the relationship between neutralizing antibody concentration/avidity and HI titer, and explains quantitative aspects of the HI assay, such as robustness to pipetting errors and detection limit. We applied our model to infer avidities against the pandemic 2009 H1N1 influenza virus in vaccinated patients (n = 45) after hematopoietic stem cell transplantation (HSCT) and validated our results with independent avidity measurements using an enzyme-linked immunosorbent assay with urea elution. Avidities inferred by the model correlated with experimentally determined avidities (ρ = 0.54, 95% CI = [0.31, 0.70], P < 10⁻⁴). The model predicted that increases in IgG concentration mainly contribute to the observed HI titer increases in HSCT patients and that immunosuppressive treatment is associated with lower baseline avidities. Since our approach requires only easy-to-establish measurements as input, we anticipate that it will help to disentangle causes for poor vaccination outcomes also in larger patient populations. This study demonstrates that biophysical modelling can provide quantitative insights into agglutination assays and complement experimental measurements to refine antibody response analyses.     

Plasmodium berghei sporozoites in nonreplicative vacuole are eliminated by a PI3P‐mediated autophagy‐independent pathway

The protozoan parasite Plasmodium, causative agent of malaria, invades hepatocytes by invaginating the host cell plasma membrane and forming a parasitophorous vacuole membrane (PVM). Surrounded by this PVM, the parasite undergoes extensive replication. Parasites inside a PVM provoke the Plasmodium‐associated autophagy‐related (PAAR) response. This is characterised by a long‐lasting association of the autophagy marker protein LC3 with the PVM, which is not preceded by phosphatidylinositol 3‐phosphate (PI3P)‐labelling. Prior to productive invasion, sporozoites transmigrate several cells and here we describe that a proportion of traversing sporozoites become trapped in a transient traversal vacuole, provoking a host cell response that clearly differs from the PAAR response. These trapped sporozoites provoke PI3P‐labelling of the surrounding vacuolar membrane immediately after cell entry, followed by transient LC3‐labelling and elimination of the parasite by lysosomal acidification. Our data suggest that this PI3P response is not only restricted to sporozoites trapped during transmigration but also affects invaded parasites residing in a compromised vacuole. Thus, host cells can employ a pathway distinct from the previously described PAAR response to efficiently recognise and eliminate Plasmodium parasites.     

Control of soil pH on turnover of belowground organic matter in subalpine grassland

Grasslands store substantial amounts of carbon in the form of organic matter in soil and roots. At high latitudes and elevation, turnover of these materials is slow due to various interacting biotic and abiotic constraints. Reliable estimates on the future of belowground carbon storage in cold grassland soils thus require quantitative understanding of these factors. We studied carbon turnover of roots, labile coarse particulate organic matter (cPOM) and older non-cPOM along a natural pH gradient (3.9–5.9) in a subalpine grassland by utilizing soil fractionation and radiocarbon dating. Soil carbon stocks and root biomass, turnover, and decomposability did not scale with soil pH whereas mean residence times of both soil organic matter fractions significantly increased with declining pH. The effect was twice as strong for non-cPOM, which was also stronger enriched in ¹⁵N at low pH. Considering roots as important precursors for cPOM, the weaker soil pH effect on cPOM turnover may have been driven by comparably high root pH values. At pH < 5, long non-cPOM mean residence times were probably related to pH dependent changes in substrate availability. Differences in turnover along the pH gradient were not reflected in soil carbon stocks because aboveground productivity was lower under acidic conditions and, in turn, higher inputs from aboveground plant residues compensated for faster soil carbon turnover at less acidic pH. In summary, the study provides evidence for a strong and differential regulatory role of pH on the turnover of soil organic matter that needs consideration in studies aiming to quantify effects of changing environmental conditions on belowground carbon storage.     

Dumpy-30 family members as determinants of male fertility and interaction partners of metal-responsive transcription factor 1 (MTF-1) in Drosophila

Background

Human clinical studies and mouse models clearly demonstrate that cytomegalovirus (CMV) disrupts normal organ and tissue development. Although CMV is one of the most common causes of major birth defects in humans, little is presently known about the mechanism(s) underlying CMV-induced congenital malformations. Our prior studies have demonstrated that CMV infection of first branchial arch derivatives (salivary glands and teeth) induced severely abnormal phenotypes and that CMV has a particular tropism for neural crest-derived mesenchyme (NCM). Since early embryos are barely susceptible to CMV infection, and the extant evidence suggests that the differentiation program needs to be well underway for embryonic tissues to be susceptible to viral infection and viral-induced pathology, the aim of this study was to determine if first branchial arch NCM cells are susceptible to mCMV infection prior to differentiation of NCM derivatives.

Results

E11 mouse mandibular processes (MANs) were infected with mouse CMV (mCMV) for up to 16 days in vitro. mCMV infection of undifferentiated embryonic mouse MANs induced micrognathia consequent to decreased Meckel's cartilage chondrogenesis and mandibular osteogenesis. Specifically, mCMV infection resulted in aberrant stromal cellularity, a smaller, misshapen Meckel's cartilage, and mandibular bone and condylar dysmorphogenesis. Analysis of viral distribution indicates that mCMV primarily infects NCM cells and derivatives. Initial localization studies indicate that mCMV infection changed the cell-specific expression of FN, NF-κB2, RelA, RelB, and Shh and Smad7 proteins.

Conclusion

Our results indicate that mCMV dysregulation of key signaling pathways in primarily NCM cells and their derivatives severely disrupts mandibular morphogenesis and skeletogenesis. The pathogenesis appears to be centered around the canonical and noncanonical NF-κB pathways, and there is unusual juxtaposition of abnormal stromal cells and surrounding matrix. Moreover, since it is critically important that signaling molecules are expressed in appropriate cell populations during development, the aberrant localization of components of relevant signaling pathways may reveal the pathogenic mechanism underlying mandibular malformations.     

Ectomycorrhiza succession patterns in Pinus sylvestris forests after stand-replacing fire in the Central Alps

Fires shape fundamental properties of many forest ecosystems and climate change will increase their relevance in regions where fires occur infrequently today. In ecosystems that are not adapted to fire, post-fire tree recruitment is often sparse, a fact that might be attributed to a transient lack of mycorrhizae. Ectomycorrhizal (EcM) fungi play an important role for recruitment by enhancing nutrient and water uptake of their hosts. The questions arise whether and for how long the EcM community is transformed by fire. We investigated the resistance and resilience of EcM fungal communities on a chronosequence of 12 Pinus sylvestris stands in Valais (Switzerland) and Val d’Aosta (Italy) affected by fire between 1990 and 2006. Soil samples from burnt and non-burnt forests were analyzed with respect to EcM fungi by means of a bioassay. The number of EcM species was significantly lower in samples from recently (2–5 years) burnt sites than non-burnt forest, and increased with time since fire reaching levels of adjacent forests after 15–18 years. Community composition changed after fire but did not converge to that of non-burnt sites over the 18 year period. Only Rhizopogon roseolus and Cenococcum geophilum were abundant in both burnt sites and adjacent forest. Our data indicate fire resistance of some EcM fungal species as well as rapid resilience in terms of species number, but not in species composition. As long as the function of different EcM species for seedling establishment is unknown, the consequences of long-term shifts in EcM community composition for tree recruitment remain unclear.