Deployment of a ordered transposon mutant library in a quorum-competent genetic background.

, the causative agent of cholera, has sparked seven pandemics in recent centuries, with the current one being the most prolonged. pathogenesis hinges on its ability to switch between low and high cell density gene regulatory states, enabling transmission between host and the environment. Previously, a transposon mutant library for was created to support investigations aimed toward uncovering the genetic determinants of its pathogenesis.

Discovery of positive and purifying selection in metagenomic time series of hypermutator microbial populations.

A general method to infer both positive and purifying selection during the real-time evolution of hypermutator pathogens would be broadly useful. To this end, we introduce a Simple Test to Infer Mode of Selection (STIMS) from metagenomic time series of evolving microbial populations. We test STIMS on metagenomic data generated by simulations of bacterial evolution, and on metagenomic data spanning 62,750 generations of Lenski's long-term evolution experiment with Escherichia coli (LTEE).

Maintenance of Metabolic Plasticity despite Relaxed Selection in a Long-Term Evolution Experiment with .

AbstractTraits that are unused in a given environment are subject to processes that tend to erode them, leading to reduced fitness in other environments. Although this general tendency is clear, we know much less about why some traits are lost while others are retained and about the roles of mutation and selection in generating different responses. We addressed these issues by examining populations of a facultative anaerobe, , that have evolved for >30 years in the presence of oxygen, with relaxed selection for anaerobic growth and the associated metabolic plasticity.

Model Systems in Ecology, Evolution, and Behavior: A Call for Diversity in Our Model Systems and Discipline.

AbstractEcologists and evolutionary biologists are fascinated by life's variation but also seek to understand phenomena and mechanisms that apply broadly across taxa. Model systems can help us extract generalities from amid all the wondrous diversity, but only if we choose and develop them carefully, use them wisely, and have a range of model systems from which to choose. In this introduction to the Special Feature on Model Systems in Ecology, Evolution, and Behavior (EEB), we begin by grappling with the question, What a model system? We then explore where our model systems come from, in terms of the skills and other attributes required to develop them and the historical biases that influence traditional model systems in EEB.

Changes in Cell Size and Shape during 50,000 Generations of Experimental Evolution with Escherichia coli.

Bacteria adopt a wide variety of sizes and shapes, with many species exhibiting stereotypical morphologies. How morphology changes, and over what timescales, is less clear. Previous work examining cell morphology in an experiment with showed that populations evolved larger cells and, in some cases, cells that were less rod-like.

Divergent Evolution of Mutation Rates and Biases in the Long-Term Evolution Experiment with Escherichia coli.

All organisms encode enzymes that replicate, maintain, pack, recombine, and repair their genetic material. For this reason, mutation rates and biases also evolve by mutation, variation, and natural selection. By examining metagenomic time series of the Lenski long-term evolution experiment (LTEE) with Escherichia coli (Good BH, McDonald MJ, Barrick JE, Lenski RE, Desai MM.

Genomic and phenotypic evolution of in a novel citrate-only resource environment.

Evolutionary innovations allow populations to colonize new ecological niches. We previously reported that aerobic growth on citrate (Cit) evolved in an population during adaptation to a minimal glucose medium containing citrate (DM25). Cit variants can also grow in citrate-only medium (DM0), a novel environment for .

Sustained fitness gains and variability in fitness trajectories in the long-term evolution experiment with Escherichia coli.

Many populations live in environments subject to frequent biotic and abiotic changes. Nonetheless, it is interesting to ask whether an evolving population's mean fitness can increase indefinitely, and potentially without any limit, even in a constant environment. A recent study showed that fitness trajectories of Escherichia coli populations over 50 000 generations were better described by a power-law model than by a hyperbolic model.