Leinweber Anne, Weigert Michael, Kümmerli Rolf
Department of Plant and Microbial Biology, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
Evolution. 2018 Apr 17;72(7):1515-28. doi: 10.1111/evo.13491.
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 interspecific 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 upregulates 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 costly. Altogether, our results demonstrate that phenotypic plasticity in siderophore production plays an important role in interspecific competition for iron. Upregulating siderophore production may be a powerful strategy to lock iron away from competing species, and to reserve this nutrient for strain members possessing the compatible receptor for uptake.
在高等生物中，对竞争做出反应的表型可塑性是一种已被充分描述的现象。在此，我们表明细菌也有能力感知竞争者的存在，并做出微调反应以适应竞争的普遍水平。在我们的实验中，我们研究了铜绿假单胞菌（PA）与其竞争者洋葱伯克霍尔德菌（BC）之间对铁的种间竞争。我们关注PA在表型上调节绿脓菌素（一种铁螯合铁载体）产生的能力。我们发现，在铁可用性低的竞争条件下，PA在竞争早期会上调绿脓菌素的产生。这种可塑性上调是根据BC施加的竞争水平进行微调的，并且似乎以更早开始生长的形式为PA带来相对适合度优势。然而，在后期，与单培养相比，PA在混合培养中的生长出现下降，这表明竞争反应是有代价的。总之，我们的结果表明，铁载体产生中的表型可塑性在铁的种间竞争中起重要作用。上调铁载体的产生可能是一种强大的策略，可将铁从竞争物种中锁定，并为拥有兼容摄取受体的菌株成员保留这种营养物质。
