Differences in pili structure modulate bacterial behavior

Type IV pili, or T4P, are hairlike protein appendages on the surface of bacteria that can retract to assist in movement and DNA uptake or resist retraction to promote adhesion and bacterial aggregation. Strains of Acinetobacter bacteria show differences in the balance of these T4P-dependent behaviors, but it is unclear why these differences occur.

Kurt Piepenbrink, University of Nebraska, Nebraska Center for Biotechnology Microscopy Core Research Facility

Scanning Electron Microscopy image of Acinetobacter nosocomialis with artificially enhanced pilus fibers in green, cyan and magenta.

Yafan Yu and colleagues from the University of Georgia and the University of Nebraska–Lincoln published a study in the Journal of Biological Chemistry demonstrating how differences in pilus structure affect bacterial behavior. Researchers compared two Acinetobacter strains, International Clone I, or IC-I, and International Clone II, or IC-II, which differ in the sequence of PilA, the main subunit and building block of T4P. For direct comparison of pilus structure and function, they created genetically identical strains by replacing the native PilA gene with IC-I or IC-II variants. They found that IC-I PilA formed pili with efficient retraction behavior, promoting motility and DNA uptake. In contrast, the IC-II PilA produced pili that resisted retraction, leading to increased surface pili and biofilm formation.

These results illustrate that small changes in pilus structure can affect bacterial behavior, demonstrating how similar bacterial strains adapt to different environments. Future research can investigate how targeting the T4P structure to control pilus retraction and adhesion can open new avenues for complementary, targeted antibacterial therapeutics.