GSE129161
Rapid accumulation of motility-activating mutations in resting liquid culture of Escherichia coli
Expression and use of motility genes is a potentially beneficial but costly process in bacteria. Interestingly, many isolate strains of Escherichia coli possess motility genes but have lost the ability to activate them in conditions in which motile cells are advantageous, raising the question of how they respond to these situations. Through transcriptome profiling of strains in the E. coli single-gene knockout Keio collection, we noticed drastic upregulation of motility genes in many of the deletion strains as compared to its typically non-motile parent strain (BW25113). This switch to a motile phenotype is not a direct consequence of the genes deleted, but is instead due to a variety of secondary mutations that increase the synthesis of the major motility regulator, FlhDC. We found that a phenotypic switch to motility at a population level can be induced in non-motile E. coli strains by incubation in non-shaking liquid medium overnight but not in shaking media. Individual isolates after the overnight incubation acquired distinct mutations upstream of the flhDC operon, including different insertion sequence (IS) elements and, to a lesser extent, point mutations. The rapid sweep in the non-shaking population shows that non-motile strains without existing regulatory mechanisms can quickly adapt to a motile lifestyle by quickly acquired genetic changes. Overall design: 71 RNA-seq experiments on knockout strains from the Keio E. coli knockout collection grown in MOPS Minimal liquid media