Temperature-dependent molecular cell membrane adaptation of microbial populations from a permafrost region

Permafrost is a common feature in polar regions. The uppermost permafrost layer, thawed in summer, is characterized by an extreme temperature regime from about +15°C to 35°C. Even so a diverse range of microorganisms have been discovered in this so-called active layer.The aim of the current study was to examine as to how the microbial populations within the different horizons of the active layer were adapted to the extreme variable temperature regime of the permafrost area. Thus, two soil samples were taken from the active layer on the island Samoylov in the southern Lena delta, Siberia: one surface-near sample (11-18 cm) and one permafrost-near sample (25-32 cm). Aliquots of each sample were incubated under 4 °C and 28 °C for about 4 weeks. Subsequently, the molecular cell membrane composition (phospholipids) was qualitatively and quantitatively evaluated using HPLC-ESI-MS/MS. To maintain the membrane fluidity at low temperatures, microbial cells can decrease their solid-liquid phase transition temperatures below the ambient temperature. They change their phospholipid fatty acid composition to more bulky-shaped cis-unsaturated fatty acids and/or to more shorter-chain fatty acid, because of the lower melting temperatures of unsaturated and shorter-chain fatty acids. The comparison of the phospholipid fatty acid (PLFA) distribution of the different horizons at 4 and 28 °C shows that the microbial population of both horizons does not incorporate significantly more unsaturated fatty acids under cooler conditions. In contrast to this the surface near as well as the permafrost near microbial communities reveal for both a distinct relative increase of short chain fatty acids of 7.3 and 10.3% in the 4 °C incubation experiment.In addition to this distinct chain length adaptation, the PLFA proportions of the microbial population of the active layer differ with the different depth horizons. The permafrost near microbial community shows, in general, a higher relative proportion of unsaturated and shorter chain fatty acids. This indicates a stronger adaptation to cooler environmental conditions, whereas the surface near population reveals a higher flexibility towards warmer temperature conditions

Deficits in verbal fluency in presymptomatic C9orf72 mutation gene carriers-a developmental disorder

Background: A mutation in C9orf72 constitute a cross-link between amyotrophic lateral sclerosis (ALS) and fronto-temporal dementia (FTD). At clinical manifestation, both patient groups may present with either cognitive impairment of predominantly behaviour or language (in FTD) or motor dysfunctions (in ALS). Methods: In total, 36 non-symptomatic mutation carriers from ALS or FTD families were examined, including 21 subjects with C9orf72 and 15 with SOD1 mutations. Data were compared with 91 age-matched, education-matched and gender-matched healthy subjects (56 were first-degree relatives from ALS or FTD families, 35 with no known family history of ALS/FTD). MRI scanning for diffusion tensor imaging was performed to map fractional anisotropy (FA). Subjects performed an extensive neuropsychological assessment to address verbal fluency, language, executive, memory and visuospatial function. Measurements were repeated after 12 months. Results: C9orf72 expansion carriers performed significantly worse in verbal fluency and non-verbal memory and presented with distinct alterations in structural white matter integrity indicated by lower FA values in inferior and orbitofrontal cortical areas compared with carriers of SOD1 mutations or healthy subjects. Loss of structural integrity was associated with decreased verbal fluency performance. White matter alterations and cognitive performance showed no changes over 12 months in all subjects. Discussion: Reduced verbal fluency performance seems to be a distinct clinical feature of C9orf72 carriers before symptomatic disease onset without evidence for change over time in our cohort. The results support the emerging hypothesis of a general disorder in development in addition to neurodegeneration in C9orf72 carriers

Analysis of Legionella Metabolism by Pathogen Vacuole Proteomics

The causative agent of Legionnaires' disease, Legionella pneumophila, replicates in free-living amoebae as well as in macrophages of the innate immune system within a distinct membrane-bound compartment, the "Legionella-containing-vacuole" (LCV). LCV formation is a complex process and requires the bacterial Icm/Dot type IV secretion system, which translocates approximately 300 different "effector" proteins. Intact LCVs from infected Dictyostelium discoideum amoebae or RAW 264.7 murine macrophages can be purified using a straightforward protocol. In the first step, the LCVs in cell homogenates are tagged with an antibody directed against an L. pneumophila effector protein specifically localizing to the pathogen vacuole membrane and isolated by immunomagnetic separation using a secondary antibody coupled to magnetic beads. In the second step, the LCVs are further enriched by density gradient centrifugation through a Histodenz cushion. LCVs thus purified are analyzed by mass spectrometry-based proteomics and characterized by biochemical and cell biological approaches