Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA.
mSphere. 2024 Sep 25;9(9):e0039024. doi: 10.1128/msphere.00390-24. Epub 2024 Aug 28.
Twitching motility is a form of bacterial surface translocation powered by the type IV pilus (T4P). It is frequently analyzed by interstitial colony expansion between agar and the polystyrene surfaces of petri dishes. In such assays, the twitching motility of was observed with MacConkey but not Luria-Bertani (LB) agar media. One difference between these two media is the presence of bile salts as a selective agent in MacConkey but not in LB. Here, we demonstrate that the addition of bile salts to LB allowed to display twitching. Similarly, bile salts enhanced the twitching of and in LB. These observations suggest that there is a common mechanism, whereby bile salts enhance bacterial twitching and promote interstitial colony expansion. Bile salts disrupt lipid membranes and apply envelope stress as detergents. Surprisingly, their stimulatory effect on twitching appears not to be related to a bacterial physiological response to stressors. Rather, it is due to their ability to alter the physicochemical properties of a twitching surface. We observed that while other detergents promoted twitching like bile salts, stresses applied by antibiotics, including the outer membrane-targeting polymyxin B, did not enhance twitching motility. More importantly, bacteria displayed increased twitching on hydrophilic surfaces such as those of glass and tissue culture-treated polystyrene plastics, and bile salts no longer stimulated twitching on these surfaces. Together, our results show that altering the hydrophilicity of a twitching surface significantly impacts T4P functionality.
The bacterial type IV pilus (T4P) is a critical virulence factor for many medically important pathogens, some of which are prioritized by the World Health Organization for their high levels of antibiotic resistance. The T4P is known to propel bacterial twitching motility, the analysis of which provides a convenient assay for T4P functionality. Here, we show that bile salts and other detergents augment the twitching of multiple bacterial pathogens. We identified the underlying mechanism as the alteration of surface hydrophilicity by detergents. Consequently, hydrophilic surfaces like those of glass or plasma-treated polystyrene promote bacterial twitching, bypassing the requirement for detergents. The implication is that surface properties, such as those of tissues and medical implants, significantly impact the functionality of bacterial T4P as a virulence determinant. This offers valuable insights for developing countermeasures against the colonization and infection by bacterial pathogens of critical importance to human health on a global scale.
菌毛是一种细菌表面迁移形式，由 IV 型菌毛（T4P）提供动力。它经常通过琼脂和培养皿聚苯乙烯表面之间的间质菌落扩张来分析。在这样的测定中，观察到了 在用 MacConkey 但不用 Luria-Bertani（LB）琼脂培养基时的菌毛迁移。这两种培养基的一个区别是 MacConkey 中有胆盐作为选择性试剂，而 LB 中没有。在这里，我们证明在 LB 中添加胆盐可以使 显示菌毛迁移。同样，胆盐增强了 在 LB 中的菌毛迁移。这些观察结果表明，存在一种共同的机制，即胆盐增强细菌菌毛迁移并促进间质菌落扩张。胆盐破坏脂质膜并作为去污剂施加包膜压力。令人惊讶的是，它们对菌毛迁移的刺激作用似乎与细菌对胁迫物的生理反应无关。相反，它是由于它们改变菌毛迁移表面物理化学性质的能力。我们观察到，虽然其他去污剂像胆盐一样促进菌毛迁移，但抗生素施加的压力，包括靶向外膜的多粘菌素 B，并没有增强菌毛迁移运动。更重要的是，细菌在亲水表面（如玻璃和组织培养处理过的聚苯乙烯塑料）上显示出增加的菌毛迁移，而胆盐不再刺激这些表面上的菌毛迁移。总之，我们的结果表明，改变菌毛迁移表面的亲水性会显著影响 T4P 功能。
细菌 IV 型菌毛（T4P）是许多医学上重要病原体的关键毒力因子，其中一些病原体被世界卫生组织列为高度耐药的病原体。已知 T4P 可推动细菌菌毛迁移，分析其功能提供了 T4P 功能的方便测定。在这里，我们表明胆盐和其他去污剂增强了多种细菌病原体的菌毛迁移。我们确定了潜在的机制是去污剂对表面亲水性的改变。因此，像玻璃或等离子处理过的聚苯乙烯这样的亲水表面促进细菌菌毛迁移，从而无需去污剂。这意味着表面特性，例如组织和医疗植入物的特性，会显著影响细菌 T4P 作为毒力决定因素的功能。这为开发针对对全球人类健康具有重要意义的细菌病原体定植和感染的对策提供了有价值的见解。
