Bacterial flagellar diversity and evolution: seek simplicity and distrust it?

Flagella are the chief organelles of motility in bacteria. In recent years, several new findings have illuminated the evolution of bacterial flagella, including cut-down versions of the organelle in Buchnera, a dispensable ATPase and structural evidence for homology between FliG (a component of the flagellar motor) and MgtE (a magnesium transporter). However, a fresh examination of the phylogenetic distribution of flagellar genes warns against a simplistic model of early flagellar evolution.