PT - JOURNAL ARTICLE AU - Davi R. Ortega AU - Poorna Subramanian AU - Petra Mann AU - Andreas Kjær AU - Songye Chen AU - Kylie J. Watts AU - Sahand Pirbadian AU - David A. Collins AU - Romain Kooger AU - Marina G. Kalyuzhnaya AU - Simon Ringgaard AU - Ariane Briegel AU - Grant J. Jensen TI - Repurposing a macromolecular machine: Architecture and evolution of the F7 chemosensory system AID - 10.1101/653600 DP - 2019 Jan 01 TA - bioRxiv PG - 653600 4099 - http://biorxiv.org/content/early/2019/05/30/653600.1.short 4100 - http://biorxiv.org/content/early/2019/05/30/653600.1.full AB - How complex, multi-component macromolecular machines evolved remains poorly understood. Here we reveal the evolutionary origins of the chemosensory machinery that controls flagellar motility in Escherichia coli. We first identified ancestral forms still present in Vibrio cholerae, Pseudomonas aeruginosa, Shewanella oneidensis and Methylomicrobium alcaliphilum, characterizing their structures by electron cryotomography and finding evidence that they function in a stress response pathway. Using bioinformatics, we then traced the evolution of the system through γ-Proteobacteria, pinpointing key evolutionary events that led to the machine now seen in E. coli. Our results suggest that two ancient chemosensory systems with different inputs and outputs (F6 and F7) existed contemporaneously, with one (F7) ultimately taking over the inputs and outputs of the other (F6), which was subsequently lost.