Variation in the fatty acid profiles of two cold water diatoms grown under different temperature,light, and nutrient regimes

There is a growing demand for marine omega-3 fatty acids (FAs) that is produced in high amounts by some microalgae. Here we determined the FA profiles of two cold water adapted diatoms, Chaetoceros wighamii and Thalassiosira baltica. The cultures were acclimated to different temperatures (3, 7, 11, 15, and 19 °C) and irradiance (20, 40, 130, and 450 μmol photons m^?2 s^?1) and the FA profiles were determined in exponential and stationary growth phases, the latter induced by different nutrient limitation (N, P, and Si). The maximum growth rate was obtained by both species at 11 °C, ≥ 130 μmol photons m^?2 s^?1 and was 0.8 day^?1 and 0.6 day^?1 for C. wighamii and T. baltica, respectively. Both species contained relatively high amounts of eicosapentaenoic acid (EPA). Thalassiosira baltica accumulated maximally ~ 30 mg EPA g^?1 ash-free dry weight (AFDW) under Si-limitation. The content of docosahexaenoic acid (DHA) was lower, reaching up to 4 mg DHA g^?1 AFDW in T. baltica. The concentration of EPA correlated positively with the chlorophyll a:carbon ratio, suggesting that it is bound to membranes in the photosynthetic apparatus and the EPA content in T. baltica was high enough to consider it as a potent candidate for cultivation under cold (< 15 °C) conditions. Covering a wide range of environmental conditions, the strongest differentiation in FA profiles was observed between the species with the growth phase/nutrient limitation pattern as the second most important driver of the FA composition.

     

pH-dependent association of enolase and glyceraldehyde-3-phosphate dehydrogenase of Lactobacillus crispatus with the cell wall and lipoteichoic acids

The plasminogen-binding proteins enolase and glyceraldehyde-3-phosphate dehydrogenase of Lactobacillus crispatus were localized on the cell surface at pH 5 but released into the medium at an alkaline pH. These proteins bound to lipoteichoic acids at a pH below their isoelectric point. The results indicate that lactobacilli rapidly modify their surface properties in response to changes in pH.     

Exposure to environmental radionuclides is associated with altered metabolic and immunity pathways in a wild rodent

Wildlife inhabiting environments contaminated by radionuclides face putative detrimental effects of exposure to ionizing radiation, with biomarkers such as an increase in DNA damage and/or oxidative stress commonly associated with radiation exposure. To examine the effects of exposure to radiation on gene expression in wildlife, we conducted a de novo RNA sequencing study of liver and spleen tissues from a rodent, the bank vole Myodes glareolus. Bank voles were collected from the Chernobyl Exclusion Zone (CEZ), where animals were exposed to elevated levels of radionuclides, and from uncontaminated areas near Kyiv, Ukraine. Counter to expectations, we did not observe a strong DNA damage response in animals exposed to radionuclides, although some signs of oxidative stress were identified. Rather, exposure to environmental radionuclides was associated with upregulation of genes involved in lipid metabolism and fatty acid oxidation in the livers – an apparent shift in energy metabolism. Moreover, using stable isotope analysis, we identified that fur from bank voles inhabiting the CEZ had enriched isotope values of nitrogen: such an increase is consistent with increased fatty acid metabolism, but also could arise from a difference in diet or habitat between the CEZ and elsewhere. In livers and spleens, voles inhabiting the CEZ were characterized by immunosuppression, such as impaired antigen processing, and activation of leucocytes involved in inflammatory responses. In conclusion, exposure to low dose environmental radiation impacts pathways associated with immunity and lipid metabolism, potentially as a stress‐induced coping mechanism.     

SIGNR3‐dependent immune regulation by Lactobacillus acidophilus surface layer protein A in colitis

Intestinal immune regulatory signals govern gut homeostasis. Breakdown of such regulatory mechanisms may result in inflammatory bowel disease (IBD). Lactobacillus acidophilus contains unique surface layer proteins (Slps), including SlpA, SlpB, SlpX, and lipoteichoic acid (LTA), which interact with pattern recognition receptors to mobilize immune responses. Here, to elucidate the role of SlpA in protective immune regulation, the NCK2187 strain, which solely expresses SlpA, was generated. NCK2187 and its purified SlpA bind to the C-type lectin SIGNR3 to exert regulatory signals that result in mitigation of colitis, maintenance of healthy gastrointestinal microbiota, and protected gut mucosal barrier function. However, such protection was not observed in Signr3^−/− mice, suggesting that the SlpA/SIGNR3 interaction plays a key regulatory role in colitis. Our work presents critical insights into SlpA/SIGNR3-induced responses that are integral to the potential development of novel biological therapies for autoinflammatory diseases, including IBD.     

The Lower Mekong: an insurmountable barrier to amphibians in southern Indochina?

Geographical information system (GIS)‐based cluster analyses and comparative ecological approaches were applied to unravel the hitherto controversially discussed role of the Mekong River as a biogeographical barrier to the amphibian fauna in Indochina. Referring to the unique and independent history of the Lower Mekong, south of the Lao–Cambodian border, this approach focused on the amphibians of southern Indochina and adjacent parts of eastern Thailand. To date, 131 amphibian species have been recorded from this region. In concordance with previous studies, our GIS‐based analyses revealed that the amphibian fauna of the Cardamom Mountains, west of the Mekong, possessed no closer affinity to the herpetofauna of the Southern Annamites. In addition, a statistical comparison of ecological characters showed an occurrence of ecological differentiation among amphibians across the Lower Mekong. Our results suggest that the Lower Mekong serves as, or at least coincides with, a biogeographical barrier in southern Indochina. Here, we discuss this hypothesis, together with selected species spatial distribution patterns, their species‐specific ecological traits and the palaeogeographical background of the region. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 905–914.