Community shifts and carbon translocation within metabolically-active rhizosphere microorganisms in grasslands under elevated CO₂

International audienceThe aim of this study was to identify the microbial communities that are actively involved in the assimilation of rhizosphere-C and are most sensitive in their activity to elevated atmospheric CO2 in a temperate semi-natural low-input grassland ecosystem. For this, we analyzed 13C signatures in microbial biomarker phospholipid fatty acids (PLFA) from an in-situ 13CO2 pulse-labeling experiment in the Giessen Free Air Carbon dioxide Enrichment grasslands (GiFACE, Germany) exposed to ambient and elevated (i.e. 50% above ambient) CO2 concentrations. Short-term 13C PLFA measurements at 3 h and 10 h after the pulse-labeling revealed very little to no 13C enrichment after 3 h in biomarker PLFAs and a much greater incorporation of new plant-C into fungal compared to bacterial PLFAs after 10 h. After a period of 11 months following the pulse-labeling experiment, the 13C enrichment of fungal PLFAs was still largely present but had decreased, while bacterial PLFAs were much more enriched in 13C compared to a few hours after the pulse-labeling. These results imply that new rhizodeposit-C is rapidly processed by fungal communities and only much later by the bacterial communities, which we attributed to either a fungal-mediated translocation of rhizosphere-C from the fungal to bacterial biomass or a preferential bacterial use of dead root or fungal necromass materials as C source over the direct utilization of fresh root-exudate C in these N-limited grassland ecosystems. Elevated CO2 caused an increase in the proportional 13C enrichment (relative to the universal biomarker 16:0) of the arbuscular mycorrhizal fungal biomarker PLFA 16:1?5 and one gram-positive bacterial biomarker PLFA i16:0, but a decrease in the proportional 13C enrichment of 18:1?9c, a commonly used though questionable fungal biomarker PLFA. This suggests enhanced fungal rhizodeposit-C assimilation only by arbuscular mycorrhizal fungal species under elevated CO2

Offspring born to influenza A virus infected pregnant mice have increased susceptibility to viral and bacterial infections in early life

Influenza during pregnancy can affect the health of offspring in later life, among which neurocognitive disorders are among the best described. Here, we investigate whether maternal influenza infection has adverse effects on immune responses in offspring. We establish a two-hit mouse model to study the effect of maternal influenza A virus infection (first hit) on vulnerability of offspring to heterologous infections (second hit) in later life. Offspring born to influenza A virus infected mothers are stunted in growth and more vulnerable to heterologous infections (influenza B virus and MRSA) than those born to PBS- or poly(I:C)-treated mothers. Enhanced vulnerability to infection in neonates is associated with reduced haematopoetic development and immune responses. In particular, alveolar macrophages of offspring exposed to maternal influenza have reduced capacity to clear second hit pathogens. This impaired pathogen clearance is partially reversed by adoptive transfer of alveolar macrophages from healthy offspring born to uninfected dams. These findings suggest that maternal influenza infection may impair immune ontogeny and increase susceptibility to early life infections of offspring

Inner liner temperature variation caused deformation localisation effects in a multichannel model of a generic LRE wall structure

The inner liner of a regeneratively cooled wall of a main stage rocket combustion chamber is extremely loaded by the high temperature of the hot gas and the pressure difference between the coolant and the hot gas. A cyclic operation of such a chamber usually causes a LFC failure of the wall structure after a very low number of cycles. The development and flight qualification of such components includes on top of many other actions thermal, structural and fatigue life analyses of chamber wall structures. Often, these analyses are based on half cooling channel + half fin Finite Element models of a tiny chamber wall section with symmetry conditions at the centerline of the cooling channel and the centerline of the fin. However, injector vicinity caused chamber wall temperature variations in circumferential direction of the chamber wall may cause localization effects of the deformation of the inner liner of chamber wall structures. Exemplary, an injector vicinity caused 20 K wall temperature variation is taken into account by a three-channel model. The influence of this variation to the distribution of the circumferential strain distribution as well as to the post processing determined fatigue life is shown

Primary Liver Transplantation for Autoimmune Hepatitis: A Comparative Analysis of the European Liver Transplant Registry

The principal aim of this study was to compare the probability of and potential risk factors for death and graft loss after primary adult and pediatric liver transplantation in patients undergoing transplantation for autoimmune hepatitis (AIH) to those in patients undergoing transplantation for primary biliary cirrhosis (PBC; used as the reference group) or alcoholic cirrhosis (used as an example of a nonautoimmune liver disease). The 5-year survival of patients undergoing transplantation for AIH (n = 827) was 0.73 [95% confidence interval (CI) = 0.67-0.77]. This was similar to that of patients undergoing transplantation for alcoholic cirrhosis (0.74, 95% CI = 0.72-0.76, n = 6424) but significantly worse than that of patients undergoing transplantation for PBC (0.83, 95% CI = 0.80-0.85, n = 1588). Fatal infectious complications occurred at an increased rate in patients with AIH (hazard ratio = 1.8, P = 0.002 with PBC as the reference). The outcome of pediatric AIH patients was similar to that of adult patients undergoing transplantation up to the age of 50 years. However, the survival of AIH patients undergoing transplantation beyond the age of 50 years (0.61 at 5 years, 95% CI = 0.51-0.70) was significantly reduced in comparison with the survival of young adult AIH patients (0.78 at 18-34 years, 95% CI = 0.70-0.86) and in comparison with the survival of patients of the same age group with PBC or alcoholic cirrhosis. In conclusion, age significantly affects patient survival after liver transplantation for AN. The increased risk of dying of infectious complications in the early postoperative period, especially above the age of 50 years, should be acknowledged in the management of AIH patients with advanced-stage liver disease who are listed for liver transplantation. It should be noted that not all risk factors relevant to patient and graft survival could be analyzed with the European Liver Transplant Registry database. Liver Transpl 16:461-469, 2010. (C) 2010 AASLD

Effect of Marine Snow on Microbial Oil Degradation

In the aftermath of an oil spill, a possible response is the addition of chemical dispersants to prevent further spreading of the spilled oil on the ocean surface. The main objective is to enhance the formation of smaller oil droplets by reducing the interfacial tension between oil and water, thus dispersing the oil into the water column. The resulting solubilized oil with microdroplets along with the associated toxic compounds will be swiftly incorporated into the seawater. The formation of smaller oil droplets and the dispersant enhanced solubilized oil will increase its availability for bacteria and thus the biodegradability. Subsequently, the number and activity of oil-degrading bacteria increases, and more oil will be degraded in a shorter period of time (Kessler et al., Science 331:312–315, 2011). However, during the immediate release of the dispersed oil, volatile hydrocarbons including some of the more toxic compounds of benzene, toluene, ethylbenzene, and xylenes (BTEX) can inhibit the oil degradation (Sherry et al., Front Microbiol 5:131, 2014). Depending on the oceanic conditions, the addition of chemical dispersants can result in excessive formation of marine snow. It has been shown that the application of dispersants during phytoplankton blooms can trigger the formation of marine snow to which the sticky dispersed oil can bind. In the presence of mineral particles, oiled snow complexes are being formed that become negatively buoyant and sink to the ocean floor. As a result, oiled marine snow accumulates on the ocean floor where biodegradation is inhibited due to oxygen depletion. The abovementioned two mechanisms of inhibition of oil biodegradation upon application of oil spill dispersants will be discussed in this chapter