γ-proteobacteria eject their polar flagella under nutrient depletion, retaining flagellar motor relic structures Josie L Ferreira Forson Z Gao Florian M Rossmann Andrea Nans Susanne Brenzinger Rohola Hosseini Amanda Wilson Ariane Briegel Kai M Thormann Peter B Rosenthal Morgan Beeby 10779/crick.11359574.v1 https://crick.figshare.com/articles/journal_contribution/_-proteobacteria_eject_their_polar_flagella_under_nutrient_depletion_retaining_flagellar_motor_relic_structures/11359574 Bacteria switch only intermittently to motile planktonic lifestyles under favorable conditions. Under chronic nutrient deprivation, however, bacteria orchestrate a switch to stationary phase, conserving energy by altering metabolism and stopping motility. About two-thirds of bacteria use flagella to swim, but how bacteria deactivate this large molecular machine remains unclear. Here, we describe the previously unreported ejection of polar motors by γ-proteobacteria. We show that these bacteria eject their flagella at the base of the flagellar hook when nutrients are depleted, leaving a relic of a former flagellar motor in the outer membrane. Subtomogram averages of the full motor and relic reveal that this is an active process, as a plug protein appears in the relic, likely to prevent leakage across their outer membrane; furthermore, we show that ejection is triggered only under nutritional depletion and is independent of the filament as a possible mechanosensor. We show that filament ejection is a widespread phenomenon demonstrated by the appearance of relic structures in diverse γ-proteobacteria including Plesiomonas shigelloides, Vibrio cholerae, Vibrio fischeri, Shewanella putrefaciens, and Pseudomonas aeruginosa. While the molecular details remain to be determined, our results demonstrate a novel mechanism for bacteria to halt costly motility when nutrients become scarce. 2019-12-12 17:31:56 Flagella Gammaproteobacteria Plesiomonas Pseudomonas aeruginosa Shewanella putrefaciens Vibrio cholerae Rosenthal FC001143 SB-ack 06 Biological Sciences 11 Medical and Health Sciences 07 Agricultural and Veterinary Sciences Developmental Biology