Microbiology Monthly Newsletter for Microbiology at the Department of Cell & Molecular Biology Lundberg Laboratory, Göteborg University [ January 1999 ] [ February 1999 ] [ March 1999 ] [ April 1999 ] [ May 1999 ] [ June 1999 ] [ July-August 1999 ] [ September 1999 ] [ October 1999 ] July-August 1999 Scientific Contributions We have had a few new additions on our science display during the summer. Keep yourself updated - it’s interesting reading. New regulators involved in the osmotic stress response of Saccharomyces cerevisiae Two transcription factors, Msn2p and Msn4p, of importance for the expression of stress-protective genes in yeast have been described previously. However, it is clear that cells lacking these two factors still respond to osmotic stress by increasing the expression from many stress-inducible promoters (albeit with a reduced efficiency or altered kinetics). In a recent paper by Stefan Hohmann and coworkers, two new factors are identified as being important for this response. These proteins are Msn1p and the Nuclear Factor Hot1p and they appear to have distinct functions related to osmotic stress, i.e. they affect different target genes. Interestingly, a hot1 mutation suppresses the effects of a HOG pathway hyper-activity indicating that Hot1p may be a target of this pathway. With the addition of Msn4p and Hot1p, are all transcriptional factors involved in osmotic regulation in yeast known? No, for some genes there appears to be residual regulation even in the absence of all the Msn1p, Msn2p, Msn4p and Hot1p proteins. In other words, more to come! Autoregulation of pyruvate decarboxylase gene expression in Saccharomyces cerevisiae Saccharomyces cerevisiae possesses two isogenes, PDC1 and PDC5, encoding pyruvate decarboxylase (Pdc) which catalyses the conversion of pyruvate to acetaldedyde and carbon dioxide during alcohol fermentation. Deletion of PDC1 upregulates the activity of both the PDC1 and PDC5 promoters; a phenomenon referred to as Pdc autoregulation. Stefan and coworkers demonstrate, by using new mutated alleles of pdc1 that this autoregulation requires the Pdc1p protein but not its enzymatic activity. A model is proposed in which the autoregulation (i.e. repression of PDC1 and PDC5 promoter activity) is triggered by a certain conformational state of Pdc1p and that the mutations used, pdc1-8 and pdc1-14, which diminish Pdc activity but not repression of PDC5 are ”phase-locked” in a conformational, repression-proficient, state. Accumulation of metals by bacteriogenic iron oxides Humic substances are known to be important in metal accumulation by iron oxides. However, the biological nature of these humic substances is not well defined. In a recent paper by Karsten Pedersen and coworkers, the impact of bacteria in this sorption of metals by iron oxides has been elucidated. The model biotope is the subterranean environment and it was demonstrated that metals to a large extent partition into bacteriogenic iron oxides (BIOS). Further, bacteria of prominence in BIOS samples of the subterranean environment were identified as Gallionella ferruginea and a wide variety of heterotrophic bacteria, including stalk forms that resembles Caulobacter or Hyphomicrobium species were also present. Metals, apart from Fe, associated with BIOS samples were Na, Co, Cu, Cr, Zn, and Mn. Graduate Course Genetic Analysis of Protein Function This course is now scheduled for six consecutive Mondays (for approximately 2 hours) from November 8th to December 6th. There will be room for a maximum of eight students. PhD students interested in joining the course should e-mail Roslyn Bill at ”roslyn.bill@gmm.gu.se” giving a brief description of their research project before October 11th. More info at: http://www.cmb.gu.se/gmm/courses/function.html And remember that: "No opinion should be held with fervour. No-one holds with fervour that 7 x 8 = 56, because it is known that this is the case. Fervour is necessary only in commending an opinion which is doubtful or demonstrably false" Voltaire, quoted by Bertrand Russell Have a great month!