Above‐ and belowground linkages in Sphagnum peatland: climate warming affects plant‐microbial interactions

Peatlands contain approximately one third of all soil organic carbon (SOC). Warming can alter above‐ and belowground linkages that regulate soil organic carbon dynamics and C‐balance in peatlands. Here we examine the multiyear impact of in situ experimental warming on the microbial food web, vegetation, and their feedbacks with soil chemistry. We provide evidence of both positive and negative impacts of warming on specific microbial functional groups, leading to destabilization of the microbial food web. We observed a strong reduction (70%) in the biomass of top‐predators (testate amoebae) in warmed plots. Such a loss caused a shortening of microbial food chains, which in turn stimulated microbial activity, leading to slight increases in levels of nutrients and labile C in water. We further show that warming altered the regulatory role of Sphagnum‐polyphenols on microbial community structure with a potential inhibition of top predators. In addition, warming caused a decrease in Sphagnum cover and an increase in vascular plant cover. Using structural equation modelling, we show that changes in the microbial food web affected the relationships between plants, soil water chemistry, and microbial communities. These results suggest that warming will destabilize C and nutrient recycling of peatlands via changes in above‐ and belowground linkages, and therefore, the microbial food web associated with mosses will feedback positively to global warming by destabilizing the carbon cycle. This study confirms that microbial food webs thus constitute a key element in the functioning of peatland ecosystems. Their study can help understand how mosses, as ecosystem engineers, tightly regulate biogeochemical cycling and climate feedback in peatlands     

Effect of fertilizer levels on grain yield,incidence and severity of downy mildew in pearl millet

The effect of various levels of nitrogen (0.0, 30.0, 60.0, 120.0) and phosphorus (0.0, 6.5, 13.0, 36.0) on the incidence and severity of downy mildew of pearl millet and yield of two pearl millet varieties (Zango and GB8375) were studied under field conditions in 2000 and 2001 respectively. Both nitrogen and phosphorus significantly increased incidence and severity of the disease in the two varieties. Grain yield and 1000 grain weight of the varieties also increased with nitrogen and phosphorus levels.     

Keystone microbiome meeting 2012: a mountain top experience

The joint Keystone Symposia on ‘Innate Immunity and the Microbiome’ took place in March 2012 in Keystone, Colorado. Gabriel Nunez (U. Michigan, USA) and Akiko Iwasaki (Yale U., USA) organized sessions focused on innate immune sensing of microbe and damage signals, whilst Andrew Gewirtz (Georgia State U., USA), Fergus Shanahan (National U. Ireland, Ireland) and Ruth Ley (Cornell U., USA) organized the microbiome‐focused session. Joint and concurrent talks, and poster sessions between the groups, made for a sensational meeting with active exchange between participants. This meeting point is focused on the microbiome meeting talks and joint sessions.     

Hydrogen-deuterium exchange strategy for delineation of contact sites in protein complexes

We use NMR spectra to determine protein-protein contact sites by observing differences in amide proton hydrogen-deuterium exchange in the complex compared to the free protein in solution. Aprotic organic solvents are used to preserve H/D labeling patterns that would be scrambled in water solutions. The binding site between the mammalian co-chaperone Aha1 with the middle domain of the chaperone Hsp90 obtained by our H/D exchange method corresponds well with that in the X-ray crystal structure of the homologous complex from yeast, even to the observation of a secondary binding site. This method can potentially provide data for complexes with unknown structure and for large or dynamic complexes inaccessible via NMR and X-ray methods.     

Dendrosoter protuberans (Hymenoptera: Braconidae), An Important Elm Bark Beetle Parasitoid

The most favourable period for Dendrosoter protuberans development occurred when wasps were introduced 16 days after the beginning of Scolytus multistriatus development (the greatest number of emerged wasps per a single parasitoid female with a very positive sexual index and high percentage of parasitised elm bark beetle larvae). No significant differences were observed in parasitoid efficiency between the 11^th and the 21^st day. The most unfavourable period for elm bark beetle parasitisation was six days after the beginning of S. multistriatus development (a low reproduction of D. protuberans, a negative sexual index and a low number of destroyed S. multistriatus larvae). The reproduction of both the elm bark beetle and D. protuberans was greater in the first, than in the second generation. The developmental period of D. protuberans in the first generation was approximately two days longer than in the second generation. Furthermore, the development of females was 1-2 days longer than the development of males. D. protuberans developed most successfully on S. multistriatus (the most abundant parasitoid reproduction with the longest developmental period and a very positive sexual index that resulted in a high percentage of parasitised larvae) and then on S. ensifer, S. pygmaeus and Pteleobius kraatzi. On the other hand, S. scolytus larvae were the poorest host of all elm species - the reproduction of D. protuberans in this species was the scarcest with the shortest period of development and a negative sexual index, hence larval parasitisation was the lowest.     

Ice premelting during differential scanning calorimetry

Premelting at the surface of ice crystals is caused by factors such as temperature, radius of curvature, and solute composition. When polycrystalline ice samples are warmed from well below the equilibrium melting point, surface melting may begin at temperatures as low as -15 degrees C. However, it has been reported (. Biophys. J. 65:1853-1865) that when polycrystalline ice was warmed in a differential scanning calorimetry (DSC) pan, melting began at about -50 degrees C, this extreme behavior being attributed to short-range forces. We show that there is no driving force for such premelting, and that for pure water samples in DSC pans curvature effects will cause premelting typically at just a few degrees below the equilibrium melting point. We also show that the rate of warming affects the slope of the DSC baseline and that this might be incorrectly interpreted as an endotherm. The work has consequences for DSC operators who use water as a standard in systems where subfreezing runs are important.     

Increased Superoxide Dismutase Activity Improves Survival of Cultured Postnatal Midbrain Neurons

Abstract: Copper/zinc superoxide dismutase (Cu/Zn-SOD) is a major free radical scavenging enzyme. Increased Cu/Zn-SOD activity protects cells against oxidative stress mediated by different mechanisms. However, there is also in vitro and in vivo evidence that, in the absence of abnormal oxidative stress, chronic increased Cu/Zn-SOD activity is detrimental to living cells. To address this issue, we examined the fate of mature midbrain neurons from transgenic mice expressing human Cu/Zn-SOD and from their nontransgenic littermates. Midbrain from transgenic pups had about threefold higher Cu/Zn-SOD activity than that from nontransgenic pups. Virtually all transgenic neurons were strongly immunoreactive for human Cu/Zn-SOD protein in their cell bodies and processes. The number of midbrain neurons decreased over time in both transgenic and nontransgenic cultures, but to a significantly smaller extent in the transgenic cultures. Postnatal midbrain neurons died by either necrosis or apoptosis, and increased Cu/Zn-SOD activity attenuated both forms of cell death. Furthermore, increased Cu/Zn-SOD activity better prevented the loss of dopaminergic neurons than GABAergic neurons. We also found that neuronal processes were dramatically denser in transgenic cultures than in nontransgenic cultures. These results indicate that chronic increased Cu/Zn-SOD activity does not appear to be detrimental, but rather promotes cell survival and neuronal process development in postnatal midbrain neurons, probably by providing more efficient detoxification of free radicals. They also show that increased Cu/Zn-SOD activity does not seem to play a critical role in determining the mode of cell death in this culture system.