Uncommon Descent Serving The Intelligent Design Community

How bacteria use harpoons to speed horizontal gene transfer


A friend points out that researchers have observed bacteria using their surface appendages called competence pili to “harpoon” DNA in the environment, thus speeding up their evolution:

Abstract: Natural transformation is a broadly conserved mechanism of horizontal gene transfer in bacterial species that can shape evolution and foster the spread of antibiotic resistance determinants, promote antigenic variation and lead to the acquisition of novel virulence factors. Surface appendages called competence pili promote DNA uptake during the first step of natural transformation1; however, their mechanism of action has remained unclear owing to an absence of methods to visualize these structures in live cells. Here, using the model naturally transformable species Vibrio cholerae and a pilus-labelling method, we define the mechanism for type IV competence pilus-mediated DNA uptake during natural transformation. First, we show that type IV competence pili bind to extracellular double-stranded DNA via their tip and demonstrate that this binding is critical for DNA uptake. Next, we show that type IV competence pili are dynamic structures and that pilus retraction brings tip-bound DNA to the cell surface. Finally, we show that pilus retraction is spatiotemporally coupled to DNA internalization and that sterically obstructing pilus retraction prevents DNA uptake. Together, these results indicate that type IV competence pili directly bind to DNA via their tip and mediate DNA internalization through retraction during this conserved mechanism of horizontal gene transfer. – Courtney K. Ellison, Triana N. Dalia, Alfredo Vidal Ceballos, Joseph Che-Yen Wang, Nicolas Biais, Yves V. Brun & Ankur B. Dalia , “Retraction of DNA-bound type IV competence pili initiates DNA uptake during natural transformation in Vibrio cholerae” at Nature Microbiology, 3, pages773–780 (2018)


Well, if that’s a way bacteria evolve, what becomes of common descent and speciation? What do we mean by “bacterial species”?

Follow UD News at Twitter!

See also: Horizontal gene transfer: Sorry, Darwin, it’s not your evolution any more

We've known about this for a long time (one of the classic genetics experiments was in 1928). I'm not sure speciation works as a concept for bacteria, although there are attempts to try to get some sort of species concept (if nothing else, it's useful for classification). Bob O'H

Leave a Reply