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To stick or not to stick? Pulling pili sheds new light on biofilm formation
A pilus is an appendage on the cell surface of the majority of Gram-positive bacteria. Pili biogenesis is a machinery that involves a sortase (srtC), an enzyme that covalently assembles protein subunits (pilins) and head-to-tail series to form the backbone (PilB) inL. lactis IL1403 with a tip pilin (PilA) at the distal end of the pilus. This assembly is firmly anchored to the peptidoglycan wall by a PilC anchor pilin.
It has been demonstrated that under static conditions, pili are involved in self-aggregation and modify the architecture of a growing biofilm. To provide a deeper understanding of the role played by pili in biofilm formation, we focused on the influence of different pilins and sortase C on (i) the adhesion of cells to surfaces under dynamic conditions, and (ii) the nanomechanical properties of pili using single-molecule force spectroscopy.
We have reported that the presence of pili drastically increased the adhesion properties of L. lactison polymeric surfaces and that sortase C was mandatory for cells to sustain shear flow. Force spectroscopy experiments confirmed these requirements and provided data showing extreme flexibility of the pili, much more than DNA strands.This discovery opens up new prospects about homotypic interactions between two cells, in particular, and about self-assembly, in general. This research is ongoing.
A better understanding of the conditions that determine the bacterial colonisation of biotic (e.g., intestinal tract) or abiotic (e.g., milking machine) surfaces remains a major socio-economic issue. Deciphering the nanomechanics of pili and their importance in the adhesion oflactococcimakes it possible to provide the elements necessary to understand the possible role that they play in the formation and structuring of biofilms on relevant sites in the food-processing industry such as milking machines or wood ageing boards for cheese. Eventually, this type of biofilm would make it possible to combat pathogens (e.g.,Listeria) as well as spoilage flora, in order to propose newin finesolutions for food biopreservation.
- Mickaël CASTELAIN, email@example.com
Laboratoire d’Ingénierie des Systèmes Biologiques et des Procédés (LISBP) is a mixed research unit (UMR) attached to INRA (UMR 792), CNRS (UMR 5504) and INSA Toulouse. http://www.lisbp.fr/en/presentation_of_lisbp.html
- Jean-Christophe Piard, Institut MICALIS https://www.micalis.fr/micalis_eng/
- Muriel Mercier-Bonin, Toxalim Toulouse https://www6.toulouse.inra.fr/toxalim_eng/
- Castelain M, Duviau MP, Canette A, Schmitz P, Loubiere P, Cocaign-Bousquet M, et al. (2016) The Nanomechanical Properties of Lactococcus lactis Pili Are Conditioned by the Polymerized Backbone Pilin. PLoS One 11 (3): e0152053. http://dx.doi.org/10.1371/journal.pone.0152053
- Castelain M, Duviau MP, Oxaran V, Schmitz P, Cocaign-Bousquet M, Loubiere P, et al. (2016) Oligomerized backbone pilin helps piliatedLactococcus lactisto withstand shear flow. Biofouling 32 (8): 911-923. doi: 10.1080/08927014.2016.1213817