Yeast Hybrids in Brewing

: Microbiology has long been a keystone in fermentation and the utilization of yeast biology rein-forces molecular biotechnology as the pioneering frontier in brewing science. Consequently, modern understanding of the brewer’s yeast has faced significant refinement over the last few decades. This publication presents a condensed summation of Saccharomyces species dynamics with an emphasis on the relationship between traditional ale yeast, Saccharomyces cerevisiae, and the interspecific hybrids used in lager beer production, S. pastorianus. Introgression from other Sac-charomyces species is also touched on. The unique history of Saccharomyces cerevisiae and Saccharo-myces hybrids are exemplified by recent genomic sequencing studies aimed at categorizing brewing strains through phylogeny and redefining Saccharomyces species boundaries. Phylogenetic investigations highlight the genomic diversity of Saccharomyces cerevisiae ale strains long known to brewers by their fermentation characteristics and phenotypes. Discoveries of genomic contribu-tions from interspecific Saccharomyces species into the genome of S. cerevisiae strains is ever more apparent with increased investigations on the hybrid nature of modern industrial and historical fermentation yeast.

Synthetic periphyton as a model community to examine species dynamics in complex microbial consortia

Phototrophic biofilms, also known as periphyton, drive crucial ecosystem processes and are subject to alterations due to a multitude of biotic and abiotic factors. In this context, understanding species dynamics in periphyton is a fundamental, yet challenging, requirement to accurately predict outcomes on functions and properties of complex communities. To address this challenge, we developed a workflow applying rational design based on existing knowledge on natural periphyton, to successfully obtain a stable, diverse and highly reproducible synthetic periphyton. We show that by using our synthetic community, with a known microbial composition, we are able to monitor dynamics of single species during periphyton development and their specific response to stressors such as increased temperature and herbicides. Importantly, we clearly demonstrate that these responses are mainly driven by species interactions and how they link to changes of community function and structure. Our synthetic periphyton is a powerful tool to perform mechanistic studies on periphyton structural and functional responses, as well as on species propagation, to any biotic and abiotic stressors and their combinations.

Recovery and analysis of ancient beetle DNA from subfossil packrat middens using high-throughput sequencing

The study of ancient DNA is revolutionizing our understanding of paleo-ecology and the evolutionary history of species. Insects are essential components in many ecosystems and constitute the most diverse group of animals. Yet they are largely neglected in ancient DNA studies. We report the results of the first targeted investigation of insect ancient DNA to positively identify subfossil insects to species, which includes the recovery of endogenous content from samples as old as ~ 34,355 ybp. Potential inhibitors currently limiting widespread research on insect ancient DNA are discussed, including the lack of closely related genomic reference sequences (decreased mapping efficiency) and the need for more extensive collaborations with insect taxonomists. The advantages of insect-based studies are also highlighted, especially in the context of understanding past climate change. In this regard, insect remains from ancient packrat middens are a rich and largely uninvestigated resource for exploring paleo-ecology and species dynamics over time.

The effects of K+-deficiency on H2O2 dynamics and sucrose in tomato

Potassium (K+) deficiency inhibits the transport of photosynthetic products and causes severe crop yield losses. However, the underlying mechanisms are poorly understood. In this study, we used two tomato lines 081018 (K+-deficiency-sensitive) and 081034 (K+-deficiency-tolerant), showing tolerance to K+ deficiency to investigate the relationship between the H2O2 and sucrose in the tomato under K+-deficiency. The H₂O₂ accumulation was increased by the low K+ condition (0.5 mM) after 8 h in 081018. The enzymes related to the metabolism of H₂O₂ were decreased, and more malondialdehyde (MDA) was produced. After 24 h, the sucrose content had accumulated significantly in the leaves, however, it was deficient in the roots, and the expression level of the sucrose transporters (SUT1) was inhibited. In 081034, the activity of antioxidant enzymes was increased under K+-deficiency, and then the H2O2 subsequently returned to the control treatment (4 mM) levels and did not produce more MDA. The sucrose content was not significantly different from the control treatment after 24 h. The expression of SUT1 was not suppressed. These results suggested that the H2O2 dynamics played different roles in the two different strains. The transportation of sucrose was suppressed by the H₂O₂ from the leaf (source) to the root (sink) in 081018, and unrestricted by the advantageous reactive oxygen species dynamics capacity in 081034.

Review of the ecosystem approach in Cumberland Sound, Nunavut, Canada

Historically, fisheries have been monitored at the individual stock level, without consideration to connectivity to other species or activities in the ecosystem. The ecosystem approach requires that the stock and fishery be seen in the context of predators, competitors, prey, by-catch impacts, other fisheries and abiotic environmental variables so that management is holistic. In this review, we describe the components of the ecosystem approach applied in the scientific investigation of fisheries in Cumberland Sound, NU. Relative to other Canadian Arctic locales with commercial fisheries operations, the Cumberland Sound area has a greater biodiversity and abundance of fish and marine mammal species These components support active fisheries for Arctic Charr, Greenland Halibut, Beluga Whale as well as Ringed, Bearded and Harp Seal. The species and their fisheries are variable in character, their ecosystem effects and their response to the environment. We describe the species dynamics and their fisheries within an ecosystem context. We briefly note the challenges to developing an overarching model of the system such as the integration of the different life histories of the species, as well as the incorporation of future non-fisheries related disturbances.

Analysis of diversity-dependent species evolution using concepts in population genetics

In this work, we consider a two-type species model with trait-dependent speciation, extinction and transition rates under an evolutionary time scale. The scaling approach and the diffusion approximation techniques which are widely used in mathematical population genetics provide modeling tools and conceptual background to assist in the study of species dynamics, and help exploring the analogy between trait-dependent species diversification and the evolution of allele frequencies in the population genetics setting. The analytical framework specified is then applied to models incorporating diversity-dependence, in order to infer effective results from processes in which the net diversification of species depends on the total number of species. In particular, the long term fate of a rare trait may be analyzed under a partly symmetric scenario, using a time-change transform technique.