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The mitochondrial genomes of dinoflagellate protists are remarkable for their highly fragmented and heterogeneous organization. Early attempts to determine their structure without 'next-generation' DNA sequencing failed to recover a defined genome. Still, it coincided in showing that the proteins coding genes, three in total, and parts of the ribosomal RNA genes were spread across a diffuse assortment of small linear fragments. In contrast, a recent study employed Illumina sequencing to assemble a 326 kbp long single-molecule, circular mitochondrial genome in the symbiotic dinoflagellate Breviolum minutum. Here, we used a combination of short- and long-read massively-parallel DNA sequencing to analyze further the mitochondrial DNA of the early-branching dinoflagellate Oxyrrhis marina. We found that the mitochondrial genome of O. marina consists of 3 linear chromosomes sized 15.9, 33.8 and 40.6 kbp for a total of 90.3 kbp. It contains the cox1, cox3 and cob genes, the same three proteins encoded in the mitochondrion of all myzozoans (Apicomplexa and Dinophyceae), some fragments of ribosomal RNA genes as well as many non-functional gene fragments and extensive noncoding DNA. Our analysis unveiled segments syntenic patterns and rearrangements encompassing coding and non-coding regions, suggesting that recombination is a pervasive process driving the evolution of these genomes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier GmbH.. All rights reserved.)

In experimental evolution, scientists evolve organisms in the lab, typically by challenging them to new environmental conditions. How best to evolve a desired trait? Should the challenge be applied abruptly, gradually, periodically, sporadically? Should one apply chemical mutagenesis, and do strains with high innate mutation rate evolve faster? What are ideal population sizes of evolving populations? There are endless strategies, beyond those that can be exposed by individual labs. We therefore arranged a community challenge, Evolthon, in which students and scientists from different labs were asked to evolve Escherichia coli or Saccharomyces cerevisiae for an abiotic stress-low temperature. About 30 participants from around the world explored diverse environmental and genetic regimes of evolution. After a period of evolution in each lab, all strains of each species were competed with one another. In yeast, the most successful strategies were those that used mating, underscoring the importance of sex in evolution. In bacteria, the fittest strain used a strategy based on exploration of different mutation rates. Different strategies displayed variable levels of performance and stability across additional challenges and conditions. This study therefore uncovers principles of effective experimental evolutionary regimens and might prove useful also for biotechnological developments of new strains and for understanding natural strategies in evolutionary arms races between species. Evolthon constitutes a model for community-based scientific exploration that encourages creativity and cooperation., Competing Interests: The authors have declared that no competing interests exist.