Castelain Mickaël, Duviau Marie-Pierre, Canette Alexis, Schmitz Philippe, Loubière Pascal, Cocaign-Bousquet Muriel, Piard Jean-Christophe, Mercier-Bonin Muriel
Université de Toulouse, INSA, UPS, INP, LISBP, 135 Avenue de Rangueil, F-31077, Toulouse, France.
INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400, Toulouse, France.
PLoS One. 2016 Mar 24;11(3):e0152053. doi: 10.1371/journal.pone.0152053. eCollection 2016.
Pili produced by Lactococcus lactis subsp. lactis are putative linear structures consisting of repetitive subunits of the major pilin PilB that forms the backbone, pilin PilA situated at the distal end of the pilus, and an anchoring pilin PilC that tethers the pilus to the peptidoglycan. We determined the nanomechanical properties of pili using optical-tweezers force spectroscopy. Single pili were exposed to optical forces that yielded force-versus-extension spectra fitted using the Worm-Like Chain model. Native pili subjected to a force of 0-200 pN exhibit an inextensible, but highly flexible ultrastructure, reflected by their short persistence length. We tested a panel of derived strains to understand the functional role of the different pilins. First, we found that both the major pilin PilB and sortase C organize the backbone into a full-length organelle and dictate the nanomechanical properties of the pili. Second, we found that both PilA tip pilin and PilC anchoring pilin were not essential for the nanomechanical properties of pili. However, PilC maintains the pilus on the bacterial surface and may play a crucial role in the adhesion- and biofilm-forming properties of L. lactis.
乳酸乳球菌乳酸亚种产生的菌毛是一种假定的线性结构，由构成主干的主要菌毛蛋白PilB的重复亚基、位于菌毛远端的菌毛蛋白PilA以及将菌毛与肽聚糖相连的锚定菌毛蛋白PilC组成。我们使用光镊力谱法测定了菌毛的纳米力学性质。单个菌毛受到光力作用，产生了使用蠕虫状链模型拟合的力-伸长光谱。受到0-200 pN力作用的天然菌毛表现出不可伸长但高度灵活的超微结构，这通过它们较短的持久长度得以体现。我们测试了一组衍生菌株，以了解不同菌毛蛋白的功能作用。首先，我们发现主要菌毛蛋白PilB和分选酶C都将主干组织成全长细胞器，并决定了菌毛的纳米力学性质。其次，我们发现菌毛蛋白PilA尖端菌毛蛋白和菌毛蛋白PilC锚定菌毛蛋白对菌毛的纳米力学性质并非必不可少。然而，PilC可将菌毛维持在细菌表面，并且可能在乳酸乳球菌的黏附及生物膜形成特性中发挥关键作用。
