Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session B10: The Many Dimensions of EvolutionInvited Live Undergrad Friendly
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Sponsoring Units: DBIO Chair: Mikhail Tikhonov, Washington University, St. Louis |
Monday, March 15, 2021 11:30AM - 12:06PM Live |
B10.00001: A purely Lamarckian ‘evolution’ permits survival of a bacterium to a lethal stressor Invited Speaker: Christopher Marx We tend to appreciate microbes for their simplicity and predictability: a population of genetically identical cells inhabiting a uniform environment is expected to behave in a uniform way. However, counter-examples to this assumption are frequently being discovered, forcing a re-examination of the relationship between genotype and phenotype. In most such examples, bacterial cells are found to split into two discrete populations, for instance growing and non-growing. Here, we report the discovery of a novel example of microbial phenotypic heterogeneity in which cells are distributed along a gradient of phenotypes, ranging from low to high tolerance of a toxic chemical. Furthermore, we demonstrate that the distribution of phenotypes changes in different growth conditions, and we use mathematical modeling to show that cells may change their phenotype either randomly or in a particular direction in response to the environment. Our work expands our understanding of how a bacterial cell’s genome, family history, and environment all contribute to its behavior, with implications for the diverse situations in which we care to understand the growth of any single-celled populations. |
Monday, March 15, 2021 12:06PM - 12:42PM Live |
B10.00002: Evolutionary dynamics in large microbial communities Invited Speaker: Benjamin Good Microbial communities drive important biochemical cycles, from the ocean to the soil to the human gut. High rates of cell turnover endow these communities with an enormous potential for rapid evolutionary change – e.g., billions of new mutations are produced within a single gut microbiome every day. Despite the potential importance of these effects, we currently know very little about the evolutionary dynamics that take place in large microbial communities, and how these dynamics might deviate from our single-species intuition. In this talk, I will describe our recent efforts to address this question using data from the human gut microbiome. I will show how population genetic analysis of sequenced fecal samples can help us quantify the typical timescales of within-host evolution, and how this might constrain the ability of a community to adapt to fluctuating environmental conditions. |
Monday, March 15, 2021 12:42PM - 1:18PM Live |
B10.00003: Attack of the Clones: What Causes Population Structure in Bacteria and How Can We Use It? Invited Speaker: William Hanage
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Monday, March 15, 2021 1:18PM - 1:54PM Live |
B10.00004: Microbial interactions across time and space Invited Speaker: Britt Koskella There is great interest in explaining microbial diverstiy, but a critical first step that is often downplayed is understanding the spatial and temporal scales that are relevant to the system. In this talk I discuss the relative importance of interactions among bacteria and phage viruses, between bacterial strains and species within a microbiome, and between a host and its symbionts to emphasize the role of evolution and coevolution in shaping diversity across scales. I focus primarly on the plant phyllosphere as a model system to explore these interactions both in natural, ecologically complex, and simple experimental systems. |
Monday, March 15, 2021 1:54PM - 2:30PM Live |
B10.00005: The ecology and evolution of collective behaior Invited Speaker: Deborah Gordon Ant colonies operate without central control, using feedback from simple olfactory interactions to regulate their activities. There are more than 14K species of ants in every habitat on Earth, using diverse stochastic algorithms, producing different feedback regimes, in different environments. These algorithms have evolved to fit the dynamics of particular environments, including energy flow, stability, and the threat of rupture. Harvester ants in the harsh but stable conditions of the desert, regulate foraging effort according to current food availability and humidity, using excitable dynamics based on the rate of contact inside the nest between returning and ourgoing foragers. The feedback system sets a default of inactivity unless conditions are favorable. For turtle ants in the tress of the tropical forest, high humidity makes activity easy but competition is high. Their trail networks are constrained to follow the network of vegetation. They use the rate of deposition of a volatile phermone to build and maintain a destributed routing network in heterogeneous enviornments, based on design preinciples that differ from the shortest paths commonly studied in ants and in network science. The feedback system sets a default of persistent activity unless coniditions are unfavorable. The diversity of ants provides opportunites and learn how collective behavior envolves to fit divere environmental dynamics. |
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