An improved protocol to purify bacterial pili from Lactobacillus rhamnosus GG based on multimodal chromatography

Pili are polymeric proteins located at the cell surface of bacteria. These filamentous proteins are essential molecular actors playing pivotal role in bacterial adhesion with the surrounding environment. These proteins are found both in Gram-negative and positive bacteria but differ in structural organization. Purifying these high molecular weight proteins is challenging and certainly has slow down their characterization. Here, we proposed a chromatography-based protocol, mainly based on multimodal chromatography, to purify sortase-dependant SpaCBA pili from Lactobacillus rhamnosus GG (LGG). LGG is a Gram-positive bacterium that display probiotic properties notably through its SpaCBA pili. This protocol does not require specific antibodies nor complex laboratory equipment since all chromatography steps can be performed simply with a syringe, including the multimodal chromatography step. This simple protocol could be useful to numerous laboratories to purify easily pili from LGG. Therefore, the present work should boost specific studies dedicated to LGG SpaCBA pili and the characterization of the interactions occurring with their protein partners at the molecular level. Moreover, this straightforward purification process might be extended to the purification of sortase-dependant pili from other gram-positive bacteria.