Functional and regulatory profiling of energy metabolism in fission yeast

Background: The control of energy metabolism is fundamental for cell growth and function and anomalies in it are implicated in complex diseases and ageing. Metabolism in yeast cells can be manipulated by supplying different carbon sources: yeast grown on glucose rapidly proliferates by fermentation, analogous to tumour cells growing by aerobic glycolysis, whereas on non-fermentable carbon sources metabolism shifts towards respiration. Results: We screened deletion libraries of fission yeast to identify over 200 genes required for respiratory growth. Growth media and auxotrophic mutants strongly influenced respiratory metabolism. Most genes uncovered in the mutant screens have not been implicated in respiration in budding yeast. We applied gene-expression profiling approaches to compare steady-state fermentative and respiratory growth and to analyse the dynamic adaptation to respiratory growth. The transcript levels of most genes functioning in energy metabolism pathways are coherently tuned, reflecting anticipated differences in metabolic flows between fermenting and respiring cells. We show that acetyl-CoA synthase, rather than citrate lyase, is essential for acetyl-CoA synthesis in fission yeast. We also investigated the transcriptional response to mitochondrial damage by genetic or chemical perturbations, defining a retrograde response that involves the concerted regulation of distinct groups of nuclear genes that may avert harm from mitochondrial malfunction. Conclusions: This study provides a rich framework of the genetic and regulatory basis of energy metabolism in fission yeast and beyond, and it pinpoints weaknesses of commonly used auxotroph mutants for investigating metabolism. As a model for cellular energy regulation, fission yeast provides an attractive and complementary system to budding yeast

Electric and thermoelectric properties of wolframite, (Fe, Mn) WO4, crystals. Caractéristiques électriques et thermoélectriques de cristaux de wolframite (Fe, Mn) WO4

Electrical conductivity and thermoelectric power of a natural crystal of wolframite having the composition (0.614 Fe, 0.386 Mn)WO₄ have been studied from 90 K to 850 K. The results have been discussed in the light of theories for hopping conduction on the basis of qualitative energy level scheme obtained theoretically. From these discussions the electrical behaviour of wolframite has been explained and the various parameters like impurity ionisation energy, intrinsic energy gap, carrier density and mobility of carriers have also been evaluated.La conductivité électrique et la puissance thermoélectrique d'un cristal naturel de wolframite avec la composition (0.614 Fe, 0.386 Mn)WO₄ ont été étudiées de 90 K jusqu'à 850 K. Les résultats ont été discutés avec l'aide des théories de la conductivité par saut et du modèle théorique qualitatif du niveau d'énergie. Ces discussions expliquent le comportement de wolframite dans un champ électrique et aident à évaluer les différents paramètres comme l'énergie d'ionisation des impuretés, la lacune énergétique intrinsèque et la concentration et la mobilité des porteurs.Guha Thakurta S. R., Dutta A. K. Electric and thermoelectric properties of wolframite, (Fe, Mn) WO4, crystals. Caractéristiques électriques et thermoélectriques de cristaux de wolframite (Fe, Mn) WO4. In: Bulletin de Minéralogie, volume 103, 1, 1980. pp. 27-32