Molecular mechanisms regulating swarming motility in Bacilli
Date
2025
Authors
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Publisher
University of Delaware
Abstract
Bacterial motility increases the odds of survival by allowing bacteria to colonize new niches, evade predators, and resist antibiotics. Specifically, motile cells are most resistant to antimicrobials when they undergo a type of surface movement called swarming motility. To swarm bacteria must increase their number of flagella which in Bacillus subtilis is controlled by the flagella chemotaxis (fla/che) operon. This operon is regulated by the master regulator of swarming motility, SwrA, and the response regulator DegU that binds to the fla/che promoter inducing expression of flagellar basal bodies. However, swarming motility can be inhibited through the adaptor-mediated degradation of SwrA by the protease LonA and its adaptor SmiA. Together, the transcriptional and translational regulation modulate the production of flagella needed for swarming, but how these processes function at the molecular level remain unclear. Here we identify that DegU tetramerizes on DNA in the presence of SwrA potentially positioning it to interact with the ⍺CTD of RNA polymerase. Furthermore, we structurally characterize SwrA and identify key conserved residues important for its transcriptional and swarming activity. Finally, we evaluate the interactions and oligomeric states of the post-translational complex identifying that SmiA interacts with both SwrA and LonA N-terminal domain (LonANTD) and that it forms heterodimers with LonANTD. Overall, our work expands and updates the transcriptional and translational molecular mechanisms of swarming regulation in Bacilli.
Description
Keywords
Activators, Adaptor, Bacilli, Response regulators, Swarming, Transcription