The bacterium Pseudomonas aeruginosa senses and gradually responds to inter-specific competition for iron

Phenotypic plasticity in response to competition is a well-described phenomenon in higher organisms. Here, we show that also bacteria have the ability to sense the presence of competitors and mount fine-tuned responses to match prevailing levels of competition. In our experiments, we studied inter-specific competition for iron between the bacterium Pseudomonas aeruginosa (PA) and its competitor Burkholderia cenocepacia (BC). We focused on the ability of PA to phenotypically adjust the production of pyoverdine, an iron-scavenging siderophore. We found that PA up-regulates pyoverdine production early on during competition under condition of low iron availability. This plastic upregulation was fine-tuned in response to the level of competition imposed by BC, and seems to confer a relative fitness benefit to PA in the form of an earlier initiation of growth. At later time points, however, PA showed reduced growth in mixed compared to monoculture, suggesting that competitive responses are co...响应竞争的表型可塑性（phenotypic plasticity）是高等生物中被广泛报道的经典现象。本研究证实，细菌同样具备感知竞争者存在的能力，并能启动精准调控的应答以适配当前的竞争强度。本实验针对铜绿假单胞菌（Pseudomonas aeruginosa，PA）与其竞争者洋葱伯克霍尔德菌（Burkholderia cenocepacia，BC）之间的铁资源种间竞争展开研究，重点探究PA通过表型调控合成绿脓杆菌素（pyoverdine）——一种夺铁型铁载体（siderophore）——的能力。研究发现，在铁可利用度较低的培养条件下，PA会在竞争初期上调绿脓杆菌素的合成量。这种可塑性上调会根据BC施加的竞争强度进行精准适配，且似乎能通过提早启动生长的方式为PA带来相对适合度优势。然而在培养后期，与纯培养体系相比，混合培养体系中的PA生长速率出现下降，这表明竞争应答机制存在协同……