Abstract
Despite decades of investigation of genetic transformation in the model Gram-positive bacterium Bacillus subtilis, the factors responsible for exogenous DNA binding at the surface of competent cells remain to be identified. Here, we report that wall teichoic acids (WTAs), cell wall-anchored anionic glycopolymers associated to numerous critical functions in Gram-positive bacteria, are involved in this initial step of transformation. Using a combination of cell wall-targeting antibiotics and fluorescence microscopy, we show that competence-specific WTAs are produced and specifically localized in the competent cells to mediate DNA binding at the proximity of the transformation apparatus. Furthermore, we propose that TuaH, a putative glycosyl transferase induced during competence, modifies competence-induced WTAs in order to promote (directly or indirectly) DNA binding. On the basis of our results and previous knowledge in the field, we propose a model for DNA binding and transport during genetic transformation in B. subtilis.
Highlights
Despite decades of investigation of genetic transformation in the model Gram-positive bacterium Bacillus subtilis, the factors responsible for exogenous DNA binding at the surface of competent cells remain to be identified
TAs include both wall teichoic acids (WTAs), which are covalently attached to PG via disaccharide linkage units, and lipoteichoic acids (LTAs), which are anchored in the cytoplasmic membrane[8]
Here, we show that WTAs, presumably modified by the putative sugar transferase TuaH, enable exogenous DNA binding, directly or indirectly, at the surface of B. subtilis competent cells
Summary
Despite decades of investigation of genetic transformation in the model Gram-positive bacterium Bacillus subtilis, the factors responsible for exogenous DNA binding at the surface of competent cells remain to be identified. We report that wall teichoic acids (WTAs), cell wall-anchored anionic glycopolymers associated to numerous critical functions in Grampositive bacteria, are involved in this initial step of transformation. HGT can occur naturally via three main mechanisms: transduction, conjugation and genetic transformation The latter involves binding and transport of high molecular-weight exogenous DNA across the cell envelope (cell wall and membrane(s)), and homologous recombination with the chromosome of the recipient cell. Very little is known about the first extracellular steps of genetic transformation in B. subtilis It is still unknown how exogenous DNA binds to the surface of competent cells. TUAs replace WTAs in the cell wall, maintaining its global negative charge[16]
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