Maite Novo

Genome-wide study of the adaptation of Saccharomyces cerevisiae to the early stages of wine fermentation.

This work was designed to identify yeast cellular functions specifically affected by the stress factors predominating during the early stages of wine fermentation, and genes required for optimal growth under these conditions. The main experimental method was quantitative fitness analysis by means of competition experiments in continuous culture of whole genome barcoded yeast knockout collections. This methodology allowed the identification of haploinsufficient genes, and homozygous deletions resulting in growth impairment in synthetic must. However, genes identified as haploproficient, or homozygous deletions resulting in fitness advantage, were of little predictive power concerning optimal growth in this medium. The relevance of these functions for enological performance of yeast was assessed in batch cultures with single strains. Previous studies addressing yeast adaptation to winemaking conditions by quantitative fitness analysis were not specifically focused on the proliferative stages. In some instances our results highlight the importance of genes not previously linked to winemaking. In other cases they are complementary to those reported in previous studies concerning, for example, the relevance of some genes involved in vacuolar, peroxisomal, or ribosomal functions. Our results indicate that adaptation to the quickly changing growth conditions during grape must fermentation require the function of different gene sets in different moments of the process. Transport processes and glucose signaling seem to be negatively affected by the stress factors encountered by yeast in synthetic must. Vacuolar activity is important for continued growth during the transition to stationary phase. Finally, reduced biogenesis of peroxisomes also seems to be advantageous. However, in contrast to what was described for later stages, reduced protein synthesis is not advantageous for the early (proliferative) stages of the fermentation process. Finally, we found adenine and lysine to be in short supply for yeast growth in some natural grape musts.

An impaired ubiquitin ligase complex favors initial growth of auxotrophic yeast strains in synthetic grape must

We used experimental evolution in order to identify genes involved in the adaptation of Saccharomyces cerevisiae to the early stages of alcoholic fermentation. Evolution experiments were run for about 200 generations, in continuous culture conditions emulating the initial stages of wine fermentation. We performed whole-genome sequencing of four adapted strains from three independent evolution experiments. Mutations identified in these strains pointed to the Rsp5p-Bul1/2p ubiquitin ligase complex as the preferred evolutionary target under these experimental conditions. Rsp5p is a multifunctional enzyme able to ubiquitinate target proteins participating in different cellular processes, while Bul1p is an Rsp5p substrate adaptor specifically involved in the ubiquitin-dependent internalization of Gap1p and other plasma membrane permeases. While a loss-of-function mutation in BUL1 seems to be enough to confer a selective advantage under these assay conditions, this did not seem to be the case for RSP5 mutated strains, which required additional mutations, probably compensating for the detrimental effect of altered Rsp5p activity on essential cellular functions. The power of this experimental approach is illustrated by the identification of four independent mutants, each with a limited number of SNPs, affected within the same pathway. However, in order to obtain information relevant for a specific biotechnological process, caution must be taken in the choice of the background yeast genotype (as shown in this case for auxotrophies). In addition, the use of very stable continuous fermentation conditions might lead to the selection of a rather limited number of adaptive responses that would mask other possible targets for genetic improvement.

Knowledge and Attitudes Towards Biotechnology of Elementary Education Preservice Teachers: The first Spanish experience

Due to the important impact that biotechnology has on current Western societies, well-informed critical citizens are needed. People prepared to make conscious decisions about aspects of biotechnology that relate to their own lives. Teachers play a central role in all education systems. Thus, the biotechnological literacy of preservice teachers is an important consideration as they will become an influential collective as future teachers of the next generation of children. The attitudes toward science (and biotechnology) that teachers have affect their behavior and influence the way they implement their daily practice of science teaching in school. This study analyzes the attitudes and knowledge of Spanish preservice teachers toward biotechnology. We designed a new survey instrument that was completed by 407 university students who were taking official degree programs in preschool and primary education. Our results point out that although they are aware of biotechnology applications, topics concerning the structure of DNA, management of genetic information inside the cell, genetically modified organism technology and the use of microorganisms as biotechnological tools were not correctly answered. According to our attitude analysis, Spanish preservice teachers could be defined as opponents of genetically modified product acquisition, supporters of biotechnology for medical purposes and highly interested in increasing their knowledge about biotechnology and other scientific advances. Our results show a positive correlation between better knowledge and more positive attitudes toward biotechnology. A Spanish preservice teacher with positive attitudes toward biotechnology tends to be a student with a strong biology background who scored good marks in our knowledge test.

New Genes Involved in Osmotic Stress Tolerance in Saccharomyces cerevisiae

Adaptation to changes in osmolarity is fundamental for the survival of living cells, and has implications in food and industrial biotechnology. It has been extensively studied in the yeast Saccharomyces cerevisiae, where the Hog1 stress activated protein kinase was discovered about 20 years ago. Hog1 is the core of the intracellular signaling pathway that governs the adaptive response to osmotic stress in this species. The main endpoint of this program is synthesis and intracellular retention of glycerol, as a compatible osmolyte. Despite many details of the signaling pathways and yeast responses to osmotic challenges have already been described, genome-wide approaches are contributing to refine our knowledge of yeast adaptation to hypertonic media. In this work, we used a quantitative fitness analysis approach in order to deepen our understanding of the interplay between yeast cells and the osmotic environment. Genetic requirements for proper growth under osmotic stress showed both common and specific features when hypertonic conditions were induced by either glucose or sorbitol. Tolerance to high-glucose content requires mitochondrial function, while defective protein targeting to peroxisome, GID-complex function (involved in negative regulation of gluconeogenesis), or chromatin dynamics, result in poor survival to sorbitol-induced osmotic stress. On the other side, the competitive disadvantage of yeast strains defective in the endomembrane system is relieved by hypertonic conditions. This finding points to the Golgi-endosome system as one of the main cell components negatively affected by hyperosmolarity. Most of the biological processes highlighted in this analysis had not been previously related to osmotic stress but are probably relevant in an ecological and evolutionary context.

Annapurna expedition game: applying molecular biology tools to learn genetics

ABSTRACT In this paper, we present an activity called ‘Annapurna Expedition’ through which students should apply basic concepts of genetics to solve a worldwide pandemic disease. Players take the role of scientists, involved in a research to find out which pathogen causes this pandemic and which could be the best way to solve it. Students have the opportunity to use BLAST software as a scientific bioinformatic tool to discover the main game’ enigmas. The activity uses game-based science learning methodology. This methodology incorporates multiple tools and resources, rely on learning by doing, guiding learners through a path of events and into a way of thinking. It provides students to take information from many sources and make decisions, to deduce a game’s obstacles, to understand complex systems and to collaborate with other classmates. The activity has been developed for a range of audiences, including high school students and pre-service teachers. A case study has been carried out with a group of 80 primary pre-service teachers from the Universitat Rovira i Virgili (URV) in Tarragona (Spain) in order to verify whether this activity was well designed, engage students and it is satisfactorily implemented.