Aneuploidy as a mechanism of adaptation to telomerase insufficiency

Cells’ survival is determined by their ability to adapt to constantly changing environment. Adaptation responses involve global changes in transcription, translation, and posttranslational modifications of proteins. In recent years, karyotype changes in adapting populations of single cell organisms have been reported in a number of studies. More recently, we have described aneuploidy as an adaptation mechanism used by populations of budding yeast Saccharomyces cerevisiae to survive telomerase insufficiency induced by elevated growth temperature. Genetic evidence suggests that telomerase insufficiency is caused by decreased levels of the telomerase catalytic subunit Est2. Here, we present experiments arguing that the underlying cause of this phenomenon may be within the telomerase RNA TLC1: changes in the expression of TLC1 as well as mutations in the TLC1 template region affect telomere length equilibrium and the temperature threshold for the induction of telomerase insufficiency. We discuss what lies at the root of telomerase insufficiency, how cell populations overcome it through aneuploidy and whether reversible aneuploidy could be an adaptation mechanism for a variety of environmental stresses

Stress modulation as a means to improve yeasts for lignocellulose bioconversion

The second-generation (2G) fermentation environment for lignocellulose conversion presents unique challenges to the fermentative organism that do not necessarily exist in other industrial fermentations. While extreme osmotic, heat, and nutrient starvation stresses are observed in sugar- and starch-based fermentation environments, additional pre-treatment-derived inhibitor stress, potentially exacerbated by stresses such as pH and product tolerance, exist in the 2G environment. Furthermore, in a consolidated bioprocessing (CBP) context, the organism is also challenged to secrete enzymes that may themselves lead to unfolded protein response and other stresses. This review will discuss responses of the yeast Saccharomyces cerevisiae to 2G-specific stresses and stress modulation strategies that can be followed to improve yeasts for this application. We also explore published –omics data and discuss relevant rational engineering, reverse engineering, and adaptation strategies, with the view of identifying genes or alleles that will make positive contributions to the overall robustness of 2G industrial strains

A consensus S. cerevisiae metabolic model Yeast8 and its ecosystem for comprehensively probing cellular metabolism

Genome-scale metabolic models (GEMs) represent extensive knowledgebases that provide a platform for model simulations and integrative analysis of omics data. This study introduces Yeast8 and an associated ecosystem of models that represent a comprehensive computational resource for performing simulations of the metabolism of Saccharomyces cerevisiae––an important model organism and widely used cell-factory. Yeast8 tracks community development with version control, setting a standard for how GEMs can be continuously updated in a simple and reproducible way. We use Yeast8 to develop the derived models panYeast8 and coreYeast8, which in turn enable the reconstruction of GEMs for 1,011 different yeast strains. Through integration with enzyme constraints (ecYeast8) and protein 3D structures (proYeast8DB), Yeast8 further facilitates the exploration of yeast metabolism at a multi-scale level, enabling prediction of how single nucleotide variations translate to phenotypic traits

Checklist of Helminths of Bats from Mexico and Central America

Based on original data obtained from fieldwork conducted from January 2008 to December 2015 and from previous records from published accounts, an updated checklist of helminth parasites of bats from Mexico and Central America is presented. The checklist has been organized in four ways, first as a helminth-host list in the state of Morelos, second as a helminth-host list with taxonomic and geographic distributional information, third as a bat-helminth list with references, and last, as a summary of the host-helminth association. A total of 105 records and 67 helminth taxa (26 trematodes, 4 cestodes, and 37 nematodes [33 adult and 5 larvae]) in 27 bat species from the families Emballonuridae, Molossidae, Mormoopidae, Natalidae, Phyllostomidae, and Vespertilionidae are presented for Mexico and Central America. Eight species of helminths are unique to Central America and ten species occur in both Mexico and the isthmus. From the helminths recorded in Mexico, 34 helminth species in 19 species of bats are present in the state of Morelos. The helminth diversity represents 58% of the total recorded thus far in Mexico, yet the diversity of bats intensively surveyed for parasites in the country represents roughly 14% of the diversity of chiropterans present. This evidence suggests that these intensive examinations are necessary to complete the helminthological record for bats, especially in areas of high endemism