Department of Biology

Bacteria interact with surfaces in the environment to form multicellular colonies called biofilms. Biofilms are involved in biofouling and infections as well as increasing resistance to antibacterial agents. Some bacterial species sense surfaces and/or adhere to them using type IV pili (T4P)—dynamic appendages that extend and retract. Extension and retraction are essential for many bacterial species to carry out diverse behaviors such as surface sensing, virulence, biofilm formation, and DNA uptake leading to the acquisition of antibiotic resistance genes.

Last year Courtney Ellison, a Ph.D. student in the Indiana University College of Arts and Sciences’ Department of Biology at the time, rocked the scientific world when she became the first person to observe bacteria using their pili to snatch DNA from the environment in real time.

Ellison showed that the surface sensory tad T4P of Caulobacter crescentus uses a single motor protein to power both extension and retraction.

Surface sensing leads to biofilm formation, posing a serious threat in medical settings where biofilms constitute reservoirs of antibiotic-resistant bacteria that are difficult to eliminate. These results significantly expand the understanding of basic mechanisms required for bacterial surface sensing and may lead to the development of tools to thwart surface colonization and biofilm formation.

Results of the study have been published in Science Advances. Ellison, who earned her Ph.D. in microbiology from Indiana University earlier this year, is first author on the article. Additional IU Department of Biology authors are Brun; Jennifer Chlebek, Ph.D. student; Katherine Hummels, Ph.D. graduate, 2019; and Ankur Dalia, assistant professor. Other contributors are Jingbo Kan and Nicolas Biais at CUNY Brooklyn and Gaёl Panis and Patrick Viollier at University of Geneva, Switzerland.