Biology subjects

Leale, A. M.

Publications and source records attributed to Leale, A. M..

4 recordsLinked to original sources

bioRxiv2024

S. cerevisiae serves as keystone species for spoilage resistance in experimental synthetic wine yeast communities

Species diversity is a commonly stated contributor to the fate of an invader, and thus community resistance, in both microbial and non-microbial communities. Termed the "diversity-invasion hypothesis", a positive relationship between diversity and resistance to invasion is observed when an introduced species exhibits lower levels of survival in resident communities with higher species richness. The diversity-invasion hypothesis is an attractive perspective with convincing theory and examples, yet an "invasion paradox" of contrasting results means that a positive role of diversity against invasion is still not a certainty and under debate. In this study we investigated the relationship between resistance to invasion and resident community species richness versus species identity (i.e., keystone species). Using synthetic communities comprised of combinations of four wine yeasts (Saccharomyces cerevisiae, Lachancea thermotolerans, Torulaspora delbrueckii, Starmerella bacillaris), we tracked over 21 days the presence of introduced Brettanomyces bruxellensis spoilage yeast and Lactiplantibacillus plantarum lactic acid bacteria to ask the following: 1. Does yeast community species richness impact the establishment of B. bruxellensis yeast and L. plantarum bacteria during wine fermentation? 2. How does yeast species identity influence such establishment? We found that species identity rather than richness drove the prevention of establishment of B. bruxellensis and L. plantarum, with S. cerevisiae playing a critical keystone species role. Aside from spoilage prevention by S. cerevisiae, the four resident yeast species demonstrated a strict dominance ranking of competitive exclusion regardless of background community composition. Our research lends evidence against the commonly predicted positive relationship between species richness and resistance to invasion. Furthermore, as spontaneously fermented natural wines and diverse starter cultures gain popularity, our findings support a remaining importance of S. cerevisiae in preventing B. bruxellensis spoilage..

ecology↗

bioRxiv2024

Shifts and rebound in microbial community function following repeated introduction of a novel species

Natural microbial communities continually encounter novel species that may successfully establish or simply be transient, yet both outcomes can alter the resident community composition and function. Preserving natural microbial communities and innovating synthetic ones requires insight on the immediate and long-term impact of species introductions on both composition and function. For instance, it remains unclear whether there are gradual and long-term impacts from repeated invasions where the introduced species fails to establish - so-called failed invaders. To investigate the persistent impacts by failed invaders, we present an experimental test of community stability over multiple generations against repeated novel species introduction. We propagated a natural microbial community from a traditional fermented milk beverage for approximately 100 generations, with or without, repeated introduction of Escherichia coli at each transfer. Community function was determined by metabolic profiling, and we observed alterations therein immediately after E. coli introduction, followed by recovery, or rebound once ceased. In contrast to this proxy of community function, changes in the bacterial community composition were never detected. Our results evidence that community composition and function do not necessarily respond in parallel to an introduced species, potentially due to genotypic changes below species level detection or metabolic plasticity. Our work shows an ability for functional recovery in microbial communities and contributes insight on long-term community stability to sustained disturbances.

ecology↗

bioRxiv2023

Community diversity affects functionality and species sorting during propagation of a natural microbial community

The influence of community diversity on community function has long been a central question in ecology. Particularly, the dynamics over time of this relationship as a function of levels of diversity remains unclear. Natural populations may vary in levels of species diversity, for instance after they experience disturbances that remove significant amounts of their genetic and species variation, including rare but functionally unique guilds. We investigated the influence of diversity on associated community function by propagating natural microbial communities from a traditionally fermented milk beverage diluted to various levels. Specifically, we assessed the influence of less abundant microbial types such as yeast and rarer bacterial types on community functionality and species sorting trajectories over approximately 100 generations. We observed repeatable changes in bacterial community compositions, metabolic profiles, and acidity related to starting diversity levels. The influence of a single ecological guild, yeast in our study, played a dramatic role on function, but interestingly not on long-term species sorting trajectories of the remaining bacterial community. Our results together evidence ecological selection on the microbial communities in our system and suggest an unexpected niche division between yeast and bacterial communities.

ecology↗

bioRxiv2017

The emergence, maintenance and demise of diversity in a spatially variable antibiotic regime

Antimicrobial resistance (AMR) is a growing global threat that, in the absence of new antibiotics, requires effective management of existing drugs. Here, we explore how changing patterns of drug delivery modulates the spread of resistance in a population. Resistance evolves readily under both temporal and spatial variation in drug delivery and fixes rapidly under temporal, but not spatial, variation. Resistant and sensitive genotypes coexist in spatially varying conditions due to a resistance-growth rate trade-off which, when coupled to dispersal, generates negative frequency-dependent selection and a quasi-protected polymorphism. Coexistence is ultimately lost, however, because resistant types with improved growth rates in the absence of drug spread through the population. These results suggest that spatially variable drug prescriptions can delay but not prevent the spread of resistance and provide a striking example of how the emergence and eventual demise of biodiversity is underpinned by evolving fitness trade-offs.

evolutionary biology↗