Bacterial flagellar are complex transenvelope nanomachines, and both flagella number per cell and insertion pattern vary by species. For example, Bacillus subtilis assembles ~15 flagella per cell when swimming in liquid and we found that flagellar number must double in order to swarm across solid surfaces. I will discuss how a small protein SwrA controls flagellar number by inducing oligomerization of a two-component response regulator protein necessary for gene activation. I will also show that SwrA levels are restricted by a Lon/adaptor system that is antagonized when cells are in conditions that promote swarming. The talk will cover flagellar biology and behavior, fundamentals of gene activation, regulatory proteolysis, and the cell-surface contact response.