the tenth international symposium on yeasts (isy 2000) “the rising power of yeasts in science and...
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The Tenth International Symposium on Yeasts (ISY 2000)The Rising Power of Yeasts in Science and Industry
The Tenth International Symposium on Yeasts was heldat Papendal, Arnhem, The Netherlands, during 27 Au-gust^1 September 2000. It was organized by Hans vanDijken (chair), Lex Scheers (secretary), Pieter de Geus,Wendell Iverson and Ria Komen-Zimmerman under theauspices of The Netherlands Foundation for Biotechnol-ogy and the Delft University of Technology, on behalf ofthe International Commission for Yeasts (ICY). The ICYis aliated with the International Union of Microbiolog-ical Societies (IUMS) through its Mycology Division, andwas established in 1966. Its mission is to promote interna-tional interest and collaboration on yeasts through theorganisation of two series of symposia. The rst of theseries are the International Symposia on Yeasts (ISY)which are held every four years and focus on all aspectsof yeast biology and technology (e.g. ISY 2000). The sec-ond series, the International Specialized Symposia onYeasts (ISSY) are held every year between the ISY andfocus on more specic topics. So far, the ICY has com-missioned the organization of 10 ISY and 20 ISSY, whichhave been held in a range of countries.
This Tenth International Symposium on Yeasts at-tracted some 400 registrants from 40 countries. The scien-tic program was introduced by 12 plenary lectures thatprovided the foundations for several thematic sessions,and covered the broad spectrum of interest in yeast re-search. In all, 107 oral presentations and 165 poster dis-plays were delivered during the 41/2 days of meeting.Some highlights of the program are presented in the fol-lowing sections.
Functional genomic analysis. Stephen Oliver started thescientic program with a plenary paper that described asystematic analytical approach, through EUROFAN, todetermine the function of the 6000 open reading framesin Saccharomyces cerevisiae. This was followed by presen-tations that described the genomics of regulatory net-works, transporters, cell wall chitin production, log andstationary phase expression and inuences of gene positionin the chromosome on expression.
Medical mycology. This session was introduced by Ri-chard Calderone who outlined the virulence properties ofCandida albicans and the role of signal transduction pro-teins in their expression. Subsequent presentations focusedon application of molecular techniques to the taxonomic
characterisation of medically signicant yeasts, including abroad range of Candida species, Cryptococcus neoformansand Malassezia species.
Food mycology. Graham Fleet provided background tothis session by emphasizing the opportunities for innova-tion in food processing and food ingredient developmentby exploiting yeasts other than Saccharomyces cerevisiae.These opportunities were further demonstrated by otherspeakers who considered the role of Debaryomyces hanse-nii in cheese and sausage fermentations, contributions ofyeasts to the fermentation of coee beans, bioaccumula-tion of nutritionally signicant minerals by yeasts, and thediversity of food avorants produced by yeasts. The on-going problems with Zygosaccharomyces species as spoil-age yeasts, and the application of molecular methods toidentify and type food-related yeasts were also discussed.
Stress responses and signal transduction. New develop-ments in sensing mechanisms and targets for the cAMP ^protein kinase A pathway in S. cerevisiae were describedby Johan Thevelein and led to detailed discussions of thesensing and signalling phenomena related to glycerol ac-cumulation when S. cerevisiae is exposed to environmentswith high salt or high sugar concentrations. Molecularunderstanding of these responses is being exploited to de-velop more ecient strains of bakers yeast, especiallythose for fermenting high sugar bread doughs, and frozendoughs. The relationships of membrane uidity, glycogenand trehalose synthesis, and aldose reductase expression toosmostress were examined, as well as aspects of oxidativestress.
Taxonomy, phylogenetics, evolution. This session was in-troduced by a paper by Johannes van der Walt (presentedby James Barnett) that gave a critical analysis of the spe-cies concept in yeasts in relation to the development ofmolecular taxonomy. It was followed by more specicpresentations on the molecular taxonomy of ascomycetousand basidiomycetous yeasts, in general, Candida spp.,Kluyveromyces spp., Metschnikowia spp., and a reminderof the importance of integrating genomic taxonomy withthat based on morphology, biochemistry, physiology andecological considerations.
Regulation of carbon and nitrogen metabolism. The ple-nary paper by Karl-Dieter Entian provided insight intothe regulatory processes for the glycolytic, gluconeogenic
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and glyoxylate cycles. More specic papers examined theregulation of oxidative and fermentative metabolism, in-vertase/SUC genes, pyruvate decarboxylase, mitochondrial2-methylisocitrate lyase, hexose transporters, the malic en-zyme and general physiology and growth under nitrogenlimitation. All of these presentations were concerned withS. cerevisiae, and highlight the need for metabolic studieswith other yeast species.
Metabolic engineering. Isak Pretorius used a range ofexamples to show how wine yeast (S. cerevisiae) couldbe metabolically engineered or tailored to improve its fer-mentative eciency and enhance the properties and qual-ity of wine. Subsequent presentations discussed options forthe genetic manipulation of pyruvate, galactose, malicacid, xylose and methanol metabolism in yeasts and high-lighted the practical or commercial benets of these inno-vations. Production of recombinant human collagens byPichia pastoris and over- production of carotenoid pig-ments by strains of Phaa rhodozyma were discussed asfurther examples of commercial applications of metabolicengineering.
Beverages. Mike Walsh re-examined the role of oxygenin beer fermentation and emphasized the importance ofunderstanding and controlling yeast metabolism in man-aging the quality of alcoholic beverages. Further discus-sions of beer fermentation provided updates on high-grav-ity brewing and the use of ow cytometry for rapidmonitoring of the process. Acetic acid production by S.cerevisiae and other yeasts continues to be an issue in winefermentations and two presentations demonstrated the im-portance of gene manipulation and gene expression inmanaging this problem. Other papers considered the im-portance of yeast nutrients and yeast L-glucosidase activityin relation to wine avour and quality. Presentations onCachaca (a Brazilian rum-style product) and African sor-ghum beers were reminders that new and interesting yeastecology can be found in traditional, fermented beverages.
Biodiversity and ecology. In describing the many newspecies and genera of yeasts that have been isolatedfrom plants and insects recently, Andre Lachance intro-duced this session on yeast biodiversity. He concluded thatthe 700 or so currently recognized yeast species are, in allprobability, only a fraction of what really exists in nature.This view was supported by subsequent presentations thatdescribed yeast biodiversity in the forests of Russia, inAntarctica and in the permafrosts of polar regions.More specic discussions focused on the ecology andproperties of Geotrichum and halophilic black yeasts, thepotential for yeasts to form biolms, some interesting an-tagonistic interactions between killer yeasts and wood-rot-ting fungi, and a novel yeast, isolated from the guts ofwood-lice, that depended on fungal growth.
Heterologous protein production and secretion. MaartjeFranse outlined the merits and approaches of using yeasts,especially non-conventional yeasts such as Kluyveromyceslactis, for the production of commercially important pro-
teins for the pharmaceutical and food industries. This wasfollowed by several presentations that described the genet-ic construction of strains and production of human albu-min and antibody fragments by S. cerevisiae, hepatitis Bantigens, hirudin, phytase, alcohol oxidase and human al-bumin by Hansenula polymorpha, gelatins by Pichia pasto-ris, and various proteins by Yarrowia lipolytica.
Alcohol from carbohydrates; cell cycles. Barbel Hahn-Hagerdal gave a plenary paper that demonstrated howmodern understanding of yeast physiology, integratedwith applications of recombinant DNA technology, couldprovide new yeast strains with enhanced ability to producefuel ethanol from a greater diversity of substrates. Thiswas followed by a plenary presentation by Lilia Alberghi-na that examined the role of the cAMP pathway in coor-dinating growth and cell cycle progression in S. cerevisiae.Unfortunately, neither of these interesting presentationscould be followed up by more detailed sessions becausean insucient number of papers on these topics were sub-mitted.
Cell wall and occulation. Stanley Brul outlined latestdevelopments on the composition, structure and functionof yeast cell walls and related this information to applica-tions in the pharmaceutical and food industries. Otherpresentations focused on the physiology and genetics ofcell occulation in S. cerevisiae and the interesting rela-tionship of this phenomenon to pseudohyphae formation,invasive growth and starch metabolism.
Transport and energetics. With sugar and cation trans-porter genes now described, presentations in this sessionexamined the mechanisms of transport regulation in S.cerevisiae and how this is impacted by environmental in-uences. Specic degradation of transporter proteins wasdescribed by Rosario Lagunas as one of the regulatorymechanisms.
Organelle biogenesis and function. This session openedwith the presen