<p>There is something indescribably intimate about the act of interrupting one’s reading, the act of marking one’s place in a book, a subtle gesture t

Plasmids are now the primary vectors of antimicrobial resistance, but our understanding of how human industrialisation of antibiotics influenced their evolution is limited by a paucity of data predati...

Each year, IAST invites applications for post-doctoral Research Fellowships, which offer candidates an opportunity to devote themselves full-time to their research at the start of their careers. Fello...

Bacteria evolve resistance against their phage foes with a wide range of resistance strategies whose costs and benefits depend on the level of protection they confer and on the costs for maintainance....

The rapid diversification of a single lineage into novel ecological niches underpins evolution of biodiversity, with adaptive radiations being important drivers of ecological diversity across the tree...

Environmental stress reduces species growth rates, but its impact on the function of microbial communities is less clear. Here, we experimentally demonstrate that increasing salinity stress shifts com...

In simple microbial populations, the fitness effects of most selected mutations are generally taken to be constant, independent of genotype frequency. This assumption underpins predictions about evolutionary dynamics, epistatic interactions, and the maintenance of genetic diversity in populations. Here, we systematically test this assumption using beneficial mutations from early generations of the Escherichia coli Long-Term Evolution Experiment (LTEE). Using flow cytometry-based competition assays, we find that frequency-dependent fitness effects are the norm rather than the exception, occurring in approximately 80\% of strain pairs tested. Most competitions exhibit negative frequency-dependence, where fitness advantages decline as mutant frequency increases. Furthermore, we demonstrate that the strength of frequency-dependence is predictable from invasion fitness measurements, with invasion fitness explaining approximately half of the biological variation in frequency-dependent slopes. Additionally, we observe violations of fitness transitivity in several strain combinations, indicating that competitive relationships cannot always be predicted from fitness relative to a single reference strain alone. Through high-resolution measurements of within-growth cycle dynamics, we show that simple resource competition explains a substantial portion of the frequency-dependence: when faster-growing genotypes dominate populations, they deplete shared resources more rapidly, reducing the time available for fitness differences to accumulate. Our results demonstrate that even in a simple model system designed to minimize ecological complexity, subtle ecological interactions between closely related genotypes create frequency-dependent selection that can fundamentally alter evolutionary dynamics. ### Competing Interest Statement The authors have declared no competing interest.

Antimicrobial Resistance (AMR) is a major threat to public health. Plasmids are mobile genetic elements that can rapidly spread across bacterial populations, promoting the dissemination of AMR genes i...

Announcing a new program, called STEPS, to simulate the dynamics of evolving microbial populations.

The ubiquity of bacteriophages (phages) and the major evolutionary and ecological impacts they can have on their microbial hosts has resulted in phages often cited as key drivers shaping microbial com...

In this Review, Ascensao and Desai discuss how methodological advances in genotype and phenotype manipulation are transforming experimental evolution approaches and providing new insights into the und...

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