Symbiotic interactions are indispensable for metazoan function, but their origin and evolution remain elusive. We use a controlled evolution experiment to demonstrate the emergence of novel commensal interactions between Pseudomonas aeruginosa, an initially pathogenic bacterium, and a metazoan host, Caenorhabditis elegans. We show that commensalism evolves through loss of virulence, because it provides bacteria with a double fitness advantage: Increased within-host fitness and a larger host population to infect. Commensalism arises irrespective of host immune status, as the adaptive path in immunocompromised C. elegans knockouts does not differ from that in wild type. Dissection of temporal dynamics of genomic adaptation for 125 bacterial populations reveals highly parallel evolution of incipient commensalism across independent biological replicates. Adaptation is mainly achieved through frame shift mutations in the global regulator lasR and nonsynonymous point mutations in the polymerase gene rpoB that arise early in evolution. Genetic knockouts of lasR not only corroborate its role in virulence attenuation but also show that further mutations are necessary for the fully commensal phenotype. The evolutionary transition from pathogenicity to commensalism as we observe here is facilitated by mutations in global regulators such as lasR, because few genetic changes cause pleiotropic effects across the genome with large phenotypic effects. Finally, we found that nucleotide diversity increased more quickly in bacteria adapting to immunocompromised hosts than in those adapting to immunocompetent hosts. Nevertheless, the outcome of evolution was comparable across host types. Commensalism can thus evolve independently of host immune state solely as a side-effect of bacterial adaptation to novel hosts.
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http://dx.doi.org/10.1093/molbev/msv160 | DOI Listing |
Adv Exp Med Biol
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View Article and Find Full Text PDFThe evolutionary model of construction land serves as a fundamental pillar in national spatial development and planning research. However, previous studies have overlooked the "climbing" mode of construction land on three-dimensional terrains. To address this issue, utilizing elevation data and land use data from 2010 to 2020, this study employs slope analysis, intensity analysis, spatio-temporal transformation, and PLUS model to elucidate the spatial expansion process and driving forces of urban construction land in Chongqing from both two-dimensional and three-dimensional perspectives.
View Article and Find Full Text PDFMol Syst Biol
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Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 100085, Beijing, China.
The antibiotic resistance crisis, fueled by misuse and bacterial evolution, is a major global health threat. Traditional perspectives tie resistance to drug target mechanisms, viewing antibiotics as mere growth inhibitors. New insights revealed that low-dose antibiotics may also serve as signals, unexpectedly promoting bacterial growth.
View Article and Find Full Text PDFEcology
January 2025
Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo, Norway.
Many vector-borne diseases are sensitive to changes in land use and climate; hence, it is important to understand the factors that govern the vector populations. Ixodid ticks, which serve as vectors for multiple diseases, have a slow life cycle compared with many of their hosts. The observable questing population represents only a fraction of the total tick population and may include overlapping cohorts in each stage.
View Article and Find Full Text PDFEnviron Microbiol
January 2025
Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, USA.
Ecological assembly-the process of ecological community formation through species introductions-has recently seen exciting theoretical advancements across dynamical, informational, and probabilistic approaches. However, these theories often remain inaccessible to non-theoreticians, and they lack a unifying lens. Here, I introduce the assembly graph as an integrative tool to connect these emerging theories.
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