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There is now a CONTENT FREEZE for Mercury while we switch to a new platform. It began on Friday, March 10 at 6pm and will end on Wednesday, March 15 at noon. No new content can be created during this time, but all material in the system as of the beginning of the freeze will be migrated to the new platform, including users and groups. Functionally the new site is identical to the old one. webteam@gatech.edu
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Depending on the scale of observation, genomes are both organized and fluid. Here we ask how perturbing mutational forces (including recombination and horizontal gene transfer) combine with selection and gene interactions to shape genome organization and variation both within and across lineages. To assess organization on a multi-strain (pan-genome) scale, we exploit increasing numbers of closed genomes for model species to generate pan-genomes of closed genomes for E. coli C and P. aeruginosa. Using these novel pan-genomes, we show an increased co-segregation of genes that are on average within 10Kb or less when co-located within a genome.
We next build an evolutionary simulation model to assess potential mechanisms underlying this organization. A neutral evolutionary model can transiently sustain co-segregation of initially linked genes but is vulnerable on longer time-scales to perturbing mutational events. In contrast, incorporation of gene fitness interactions can produce sustainable clusters of linked and co-segregating genes, with the network of co-segregation recapitulating the network of gene interactions. Returning to data, we show that the co-segregation network for E. coli C and P. aeruginosa are modular, and most closely resemble known metabolic networks (for Pseudomonas) and regulatory networks (for E. coli). This implies cluster evolution is guided sharply by overarching organization in the form of genetic networks.
