Functional amyloids promote retention of public goods in bacteria

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 utilized 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: (1) wildtype cells retain more iron-chelating metabolites than fibril non-producers; (2) purified Fap fibrils can prevent the loss of the iron-chelators PQS (Pseudomonas quinolone signal) and pyoverdine; and (3) pyoverdine non-producers have higher fitness in ...

细菌的生长与致病力依赖于一系列分泌至胞外环境的因子。这些因子可从分泌细胞处扩散至周围环境，要么随扩散流失，要么被不产生该因子的细胞（即作弊细胞）所利用。进化理论预测，能够减少分泌因子因扩散而流失的机制更具进化优势。其中一种潜在机制便是Fap原纤维（Fap fibrils）的产生：该结构是铜绿假单胞菌（Pseudomonas aeruginosa）细胞表面的针状纤维，可短暂结合细胞分泌的多种代谢物。本研究旨在探究Fap原纤维是否能够帮助留存分泌因子——即铁螯合分子假单胞菌素（pyoverdine），从而降低不产生该因子的作弊细胞对其的利用潜力。研究结果如下：(1) 野生型细胞相较于无法产生原纤维的菌株，能够留存更多铁螯合代谢物；(2) 纯化后的Fap原纤维可阻止铁螯合剂PQS（假单胞菌喹诺酮信号，Pseudomonas quinolone signal）与假单胞菌素的流失；(3) 不产生假单胞菌素的细胞在……中具有更高的适合度。