Decarboxylation of sorbic acid by spoilage yeasts is associated with the PAD1 gene

The spoilage yeast Saccharomyces cerevisiae degraded the food preservative sorbic acid (2,4-hexadienoic acid) to a volatile hydrocarbon, identified by gas chromatography mass spectrometry as 1,3-pentadiene. The gene responsible was identified as PAD1, previously associated with the decarboxylation of the aromatic carboxylic acids cinnamic acid, ferulic acid, and coumaric acid to styrene, 4-vinylguaiacol, and 4-vinylphenol, respectively. The loss of PAD1 resulted in the simultaneous loss of decarboxylation activity against both sorbic and cinnamic acids. Pad1p is therefore an unusual decarboxylase capable of accepting both aromatic and aliphatic carboxylic acids as substrates. All members of the Saccharomyces genus (sensu stricto) were found to decarboxylate both sorbic and cinnamic acids. PAD1 homologues and decarboxylation activity were found also in Candida albicans, Candida dubliniensis, Debaryomyces hansenii, and Pichia anomala. The decarboxylation of sorbic acid was assessed as a possible mechanism of resistance in spoilage yeasts. The decarboxylation of either sorbic or cinnamic acid was not detected for Zygosaccharomyces, Kazachstania (Saccharomyces sensu lato), Zygotorulaspora, or Torulaspora, the genera containing the most notorious spoilage yeasts. Scatter plots showed no correlation between the extent of sorbic acid decarboxylation and resistance to sorbic acid in spoilage yeasts. Inhibitory concentrations of sorbic acid were almost identical for S. cerevisiae wild-type and Deltapad1 strains. We concluded that Pad1p-mediated sorbic acid decarboxylation did not constitute a significant mechanism of resistance to weak-acid preservatives by spoilage yeasts, even if the decarboxylation contributed to spoilage through the generation of unpleasant odors.     

STING-Dependent Type I IFN Production Inhibits Cell-Mediated Immunity to Listeria monocytogenes

Infection with Listeria monocytogenes strains that enter the host cell cytosol leads to a robust cytotoxic T cell response resulting in long-lived cell-mediated immunity (CMI). Upon entry into the cytosol, L. monocytogenes secretes cyclic diadenosine monophosphate (c-di-AMP) which activates the innate immune sensor STING leading to the expression of IFN-β and co-regulated genes. In this study, we examined the role of STING in the development of protective CMI to L. monocytogenes. Mice deficient for STING or its downstream effector IRF3 restricted a secondary lethal challenge with L. monocytogenes and exhibited enhanced immunity that was MyD88-independent. Conversely, enhancing STING activation during immunization by co-administration of c-di-AMP or by infection with a L. monocytogenes mutant that secretes elevated levels of c-di-AMP resulted in decreased protective immunity that was largely dependent on the type I interferon receptor. These data suggest that L. monocytogenes activation of STING downregulates CMI by induction of type I interferon.     

Analysis of the SWI/SNF chromatin-remodeling complex during early heart development and BAF250a repression cardiac gene transcription during P19 cell differentiation

The regulatory networks of differentiation programs and the molecular mechanisms of lineage-specific gene regulation in mammalian embryos remain only partially defined. We document differential expression and temporal switching of BRG1-associated factor (BAF) subunits, core pluripotency factors and cardiac-specific genes during post-implantation development and subsequent early organogenesis. Using affinity purification of BRG1 ATPase coupled to mass spectrometry, we characterized the cardiac-enriched remodeling complexes present in E8.5 mouse embryos. The relative abundance and combinatorial assembly of the BAF subunits provides functional specificity to Switch/Sucrose NonFermentable (SWI/SNF) complexes resulting in a unique gene expression profile in the developing heart. Remarkably, the specific depletion of the BAF250a subunit demonstrated differential effects on cardiac-specific gene expression and resulted in arrhythmic contracting cardiomyocytes in vitro. Indeed, the BAF250a physically interacts and functionally cooperates with Nucleosome Remodeling and Histone Deacetylase (NURD) complex subunits to repressively regulate chromatin structure of the cardiac genes by switching open and poised chromatin marks associated with active and repressed gene expression. Finally, BAF250a expression modulates BRG1 occupancy at the loci of cardiac genes regulatory regions in P19 cell differentiation. These findings reveal specialized and novel cardiac-enriched SWI/SNF chromatin-remodeling complexes, which are required for heart formation and critical for cardiac gene expression regulation at the early stages of heart development.     

Fatty acid synthase plays a role in cancer metabolism beyond providing fatty acids for phospholipid synthesis or sustaining elevations in glycolytic activity

Fatty acid synthase is over-expressed in many cancers and its activity is required for cancer cell survival, but the role of endogenously synthesized fatty acids in cancer is unknown. It has been suggested that endogenous fatty acid synthesis is either needed to support the growth of rapidly dividing cells, or to maintain elevated glycolysis (the Warburg effect) that is characteristic of cancer cells. Here, we investigate both hypotheses. First, we compared utilization of fatty acids synthesized endogenously from ¹⁴C-labeled acetate to those supplied exogenously as ¹⁴C-labeled palmitate in the culture medium in human breast cancer (MCF-7 and MDA-MB-231) and untransformed breast epithelial cells (MCF-10A). We found that cancer cells do not produce fatty acids that are different from those derived from exogenous palmitate, that these fatty acids are esterified to the same lipid and phospholipid classes in the same proportions, and that their distribution within neutral lipids is not different from untransformed cells. These results suggest that endogenously synthesized fatty acids do not fulfill a specific function in cancer cells. Furthermore, we observed that cancer cells excrete endogenously synthesized fatty acids, suggesting that they are produced in excess of requirements. We next investigated whether lipogenic activity is involved in the maintenance of high glycolytic activity by culturing both cancer and non-transformed cells under anoxic conditions. Although anoxia increased glycolysis 2–3 fold, we observed no concomitant increase in lipogenesis. Our results indicate that breast cancer cells do not have a specific qualitative or quantitative requirement for endogenously synthesized fatty acids and that increased de novo lipogenesis is not required to sustain elevations in glycolytic activity induced by anoxia in these cells.     

Economic and ecological implications of geographic bias in pollinator ecology in the light of pollinator declines

Understanding the causes and consequences of pollinator declines is a priority in ecological research. However, across much of the globe we have a poor understanding of pollinator assemblages, population trends and the ecological and economic importance of particular pollinators, due to a marked geographic bias in research effort. Here, we show that almost half the data cited in thirteen recent meta‐analyses, which ask important and diverse questions in pollination ecology, were collected in just five countries: Australia, Brazil, Germany, Spain and the USA. In contrast, the entire continent of Africa contributed only 4% of the data. We believe that the consequences of this geographic bias are severe. Foremost, pollinator assemblages (and possibly their sensitivity to ecological drivers) can greatly vary among these regions. In addition, many communities that rely on pollinators, bees in particular, for food security and wealth generation are in geographic regions where our understanding of pollination is poor. Collecting accurate information on pollinator populations in data deficient areas will allow us to identify vulnerable populations and species and so better target conservation measures. Moreover, it will help us to determine if our current understanding of pollinator losses, based on data collected in a few locations and on the species that predominate in those regions, is representative of the wide diversity of ecosystems. We propose means of collecting such data given socioeconomic constraints.     

Linking teratogen information service and birth defects registry databases to improve knowledge of birth defect status

BACKGROUND: Although teratogen information services (TISs) obtain maternal exposure information from their callers, such services often do not know if the pregnancies were affected by a birth defect. This study attempted to improve the completeness of this information for Texas Teratogen Information Service (TTIS) callers by linking their records with the Texas Birth Defects Registry (TBDR) and Texas birth certificates (TBCs). METHODS: A total of 344 expectant mothers called TTIS with expected dates of delivery between 1 January 2000 and 31 December 2001. These pregnancies were linked with TBDR and TBC data. The percentages of pregnancies with known birth defect information both before and after the linkage were compared. RESULTS: The TTIS originally collected birth defect status information for 101 of the 344 callers (29.4%) and 0.6% of all 344 callers or 2.0% of callers with birth defect status information had a pregnancy affected by a birth defect. Linking TTIS records with TBDR and TBC data helped to raise the percentage of callers with birth defect status information from 29.4% to 71.5%. Among those callers, the percentage known to have birth defects increased from 2.0% to 4.1%. The sensitivity of TTIS follow-up calls in identifying birth defects was 50%, and the specificity was 100%. CONCLUSIONS: Linking TTIS caller records with TBDR and TBC data significantly increased both the percentage of pregnancies with birth defect status information and the percentage of pregnancies identified as affected by birth defects. Such linkage may be a good approach by which TISs can increase the completeness of their birth defect status information.