Browsing by Author "Nespolo, Roberto"

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    A multi-isotope approach reveals seasonal variation in the reliance on marine resources, production of metabolic water, and ingestion of seawater by two species of coastal passerine to maintain water balance
    (2023) Navarrete, Lucas; Lubcker, Nico; Alvarez, Felipe; Nespolo, Roberto; Sanchez-Hernandez, Juan Carlos; Maldonado, Karin; Sharp, Zachary D.; Whiteman, John P.; Newsome, Seth D.; Sabat, Pablo
    Tracing how free-ranging organisms interact with their environment to maintain water balance is a difficult topic to study for logistical and methodological reasons. We use a novel combination of triple-oxygen stable isotope analyses of water extracted from plasma (delta O-16, delta O-17, delta O-18) and bulk tissue carbon (delta C-13) and nitrogen (delta N-15) isotopes of feathers and blood to estimate the proportional contribution of marine resources, seawater, and metabolic water used by two species of unique songbirds (genus Cinclodes) to maintain their water balance in a seasonal coastal environment. We also assessed the physiological adjustments that these birds use to maintain their water balance. In agreement with previous work on these species, delta C-13 and delta N-15 data show that the coastal resident and invertivore C. nigrofumosus consumes a diet rich in marine resources, while the diet of migratory C. oustaleti shifts seasonally between marine (winter) to freshwater aquatic resources (summer). Triple-oxygen isotope analysis (Delta O-17) of blood plasma, basal metabolic rate (BMR), and total evaporative water loss (TEWL) revealed that similar to 25% of the body water pool of both species originated from metabolic water, while the rest originated from a mix of seawater and fresh water. Delta O-17 measurements suggest that the contribution of metabolic water tends to increase in summer in C. nigrofumosus, which is coupled with a significant increase in BMR and TEWL. The two species had similar BMR and TEWL during the austral winter when they occur sympatrically in coastal environments. We also found a positive and significant association between the use of marine resources as measured by delta C-13 and delta N-15 values and the estimated delta O-18 values of ingested (pre-formed) water in both species, which indicates that Cinclodes do not directly drink seawater but rather passively ingest when consuming marine invertebrates. Finally, results obtained from physiological parameters and the isotope-based estimates of marine (food and water) resource use are consistent, supporting the use of the triple-oxygen isotopes to quantify the contribution of water sources to the total water balance of free-ranging birds.
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    Late Pleistocene-dated divergence between South Hemisphere populations of the non-conventional yeast L. cidri
    (2022) Villarreal, Pablo; Villarroel, Carlos; O'Donnell, Samuel; Agier, Nicolas; Quintero-Galvis, Julian; Pena, Tomas; Nespolo, Roberto; Fischer, Gilles; Varela, Cristian; Cubillos, Francisco
    Most organisms belonging to the Saccharomycotina subphylum have high genetic diversity and a vast repertoire of metabolisms and lifestyles. Lachancea cidri is an ideal yeast model for exploring the interplay between genetics, ecological function and evolution. Lachancea cidri diverged from the Saccharomyces lineage before the whole-genome duplication and is distributed across the South Hemisphere, displaying an important ecological success. We applied phylogenomics to investigate the genetic variation of L. cidri isolates obtained from Australia and South America. Our approach revealed the presence of two main lineages according to their geographic distribution (Aus and SoAm). Estimation of the divergence time suggests that SoAm and Aus lineages diverged near the last glacial maximum event during the Pleistocene (64-8 KYA). Interestingly, we found that the French reference strain is closely related to the Australian strains, with a recent divergence (405-51 YA), likely associated to human movements. Additionally, we identified different lineages within the South American population, revealing that Patagonia contains a similar genetic diversity comparable to that of other lineages in S. cerevisiae. These findings support the idea of a Pleistocene-dated divergence between South Hemisphere lineages, where the Nothofagus and Araucaria ecological niches likely favoured the extensive distribution of L. cidri in Patagonia.
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    Molecular profiling of beer wort fermentation diversity across natural Saccharomyces eubayanus isolates
    (2020) Mardones, Wladimir; Villarroel, Carlos A.; Krogerus, Kristoffer; Tapia, Sebastian M.; Urbina, Kamila; Oporto, Christian I.; O'Donnell, Samuel; Minebois, Romain; Nespolo, Roberto; Fischer, Gilles; Querol, Amparo; Gibson, Brian; Cubillos, Francisco A.
    The utilization of S. eubayanus has recently become a topic of interest due to the novel organoleptic properties imparted to beer. However, the utilization of S. eubayanus in brewing requires the comprehension of the mechanisms that underlie fermentative differences generated from its natural genetic variability. Here, we evaluated fermentation performance and volatile compound production in ten genetically distinct S. eubayanus strains in a brewing fermentative context. The evaluated strains showed a broad phenotypic spectrum, some of them exhibiting a high fermentation capacity and high levels of volatile esters and/or higher alcohols. Subsequently, we obtained molecular profiles by generating 'end-to-end' genome assemblies, as well as metabolome and transcriptome profiling of two Patagonian isolates exhibiting significant differences in beer aroma profiles. These strains showed clear differences in concentrations of intracellular metabolites, including amino acids, such as valine, leucine and isoleucine, likely impacting the production of 2-methylpropanol and 3-methylbutanol. These differences in the production of volatile compounds are attributed to gene expression variation, where the most profound differentiation is attributed to genes involved in assimilatory sulfate reduction, which in turn validates phenotypic differences in H2S production. This study lays a solid foundation for future research to improve fermentation performance and select strains for new lager styles based on aroma and metabolic profiles.