Department of Zoology, University of Oxford , Oxford , UK.
Proc Biol Sci. 2019 May 29;286(1903):20190709. doi: 10.1098/rspb.2019.0709.
The growth and virulence of bacteria depends upon a number of factors that are secreted into the environment. These factors can diffuse away from the producing cells, to be either lost or used by cells that do not produce them (cheats). Mechanisms that act to reduce the loss of secreted factors through diffusion are expected to be favoured. One such mechanism may be the production of Fap fibrils, needle-like fibres on the cell surface observed in P. aeruginosa, which can transiently bind several secreted metabolites produced by cells. We test whether Fap fibrils help retain a secreted factor, the iron-scavenging molecule pyoverdine, and hence reduce the potential for exploitation by non-producing, cheating cells. We found that: (i) wild-type cells retain more iron-chelating metabolites than fibril non-producers; (ii) purified Fap fibrils can prevent the loss of the iron-chelators PQS ( Pseudomonas quinolone signal) and pyoverdine; and (iii) pyoverdine non-producers have higher fitness in competition with fibril non-producers than with wild-type cells. Our results suggest that by limiting the loss of a costly public good, Fap fibrils may play an important role in stabilizing cooperative production of secreted factors.
细菌的生长和毒力取决于许多分泌到环境中的因素。这些因素可以从产生细胞扩散出去，要么被不产生它们的细胞丢失，要么被不产生它们的细胞利用（作弊）。预计会有利于减少通过扩散损失分泌因子的机制。一种这样的机制可能是 Fap 原纤维的产生，即在 P. aeruginosa 中观察到的细胞表面上的针状纤维，它可以暂时结合细胞产生的几种分泌代谢物。我们测试 Fap 原纤维是否有助于保留一种分泌因子，即铁螯合分子绿脓菌素，从而减少非产生、作弊细胞利用的可能性。我们发现：（i）野生型细胞比原纤维非生产者保留更多的铁螯合代谢物；（ii）纯化的 Fap 原纤维可以防止铁螯合剂 PQS（假单胞菌喹诺酮信号）和绿脓菌素的损失；（iii）与野生型细胞相比，绿脓菌素非生产者在与原纤维非生产者的竞争中具有更高的适应性。我们的结果表明，通过限制昂贵公共物品的损失，Fap 原纤维可能在稳定分泌因子的合作生产中发挥重要作用。
