Biology subjects

Nemeth, B.

Publications and source records attributed to Nemeth, B..

3 recordsLinked to original sources

bioRxiv2026

A comparison of commercially available Saccharomyces mead yeasts.

We present a comparative analysis of 13 yeasts available for mead (honey wine) fermentation, a source of Saccharomyces cerevisiae diversity that has not yet been analyzed in detail. Using genomic, phenotyping, and analytic methods, we show that currently available mead yeasts belong to various clades of the species, most commonly to the Commercial Wine clade (5 of 13 samples). Mead yeasts in this group displayed genome structure variations and occasional loss of killer activity, despite being closely related. Historic European and traditional African mead isolates with sequenced genomes were found not to be closely related to any contemporary mead yeast product. The 13 yeasts tested here displayed high variability in oenological characteristics and in aroma production. Maximum ethanol tolerance ranged from 15 to 22% v/v, however, the most tolerant strain produced lower ethanol levels and retained high fructose content in experimental meads. The most abundant aroma components produced in meads were ethyl acetate, ethyl caprylate, isoamyl alcohol, and ethyl caprate, with similar aroma profiles in members of the Commercial Wine clade, and pronounced differences among other yeasts. Our results contribute to the knowledge of Saccharomyces yeasts in various fermentation environments, adding mead to the list of alcoholic beverages with a known diversity of starter cultures. Our results may aid strain selection for honey wine fermentations and inspire strain improvement.

microbiology↗

bioRxiv2025

Commercial Saccharomyces cerevisiae baker's yeasts: strain redundancy, genome plasticity, and colonization of the sourdough environment and the human body

Leavening dough is one of the most widespread applications of fermentative yeast and the most common practice for the general public to come into contact with microbial cultures. Saccharomyces cerevisiae is the typical species used for dough making, but the evolutionary origin of strains isolated from dough is mixed. Here, using 49 newly sequenced and 183 previously described isolates from the bakery environment, we show that the traditional strains used in Europe for sourdough making are more closely related to Chinese Mantou sourdough lineages than to commercially used baker yeast strains. Surprisingly, the expansion of these traditional European strains into other human-associated niches, including the human body, has been very limited. This is in stark contrast to the Mixed-origin clade commercial baking yeasts, which consists of only a few globally distributed clonal lineages that dominate the yeast market and recurrently colonize sourdoughs and human hosts. These clonal lineages consistently maintain their ploidy, unique heterozygous chromosomal rearrangements, and stable aneuploidies in addition to several diverse structural variants. In addition to the previously known diploid and tetraploid groups of commercial isolates, we describe a widely distributed stable triploid aneuploid clonal lineage. We show that company practices and global trade help the distribution of these clonal clusters and that these yeasts are characterized by their exclusively mitotic reproduction.

microbiology↗

bioRxiv2024

Noradrenergic and Pavlovian underpinnings of compulsive versus adaptive coping strategies

BackgroundLoss of control over coping strategies can result in the development of impulsive/compulsive spectrum disorders (ICSDs) such as obsessive-compulsive disorder or trichotillomania. Rats, like humans, show individual differences in their tendency to engage in and maintain control over coping behaviours. While most rats exposed to a schedule-induced polydipsia (SIP) procedure develop controlled, moderate, polydipsic coping, some vulnerable individuals engage in excessive, compulsive drinking, or hyperdipsia. The development of hyperdipsia depends in part on noradrenergic mechanisms, as it is prevented by the noradrenaline reuptake inhibitor, atomoxetine in highly impulsive vulnerable rats. However, whether noradrenergic mechanisms also underlie the expression of well-established hyperdipsia, or if other traits, such as the ICSD-relevant sign-tracking, confer vulnerability to its development, are unknown. MethodsIn two longitudinal studies in male Sprague-Dawley rats, we investigated whether well-established hyperdipsia is influenced by atomoxetine and whether its development is predicted by sign-tracking. ResultsSign-tracking was associated with faster acquisition of SIP and the development of high or compulsive levels of SIP. Chronic atomoxetine both exacerbated hyperdipsia and increased the mRNA levels of the markers of cellular activity and plasticity c-fos and zif268, across the dorsal striatum, as revealed by qPCR assays. Atomoxetine also altered the transcriptomic landscape of the nucleus accumbens shell and the pattern of cFos and zif268 expression in the amygdalo-striatal system. ConclusionsThese results provide new insight into the biobehavioural basis of compulsive behaviours, revealing a differential noradrenergic control of the development and expression of compulsive coping, the latter involving recruitment of distinct striatal processes.

animal behavior and cognition↗