Fitness correlates with the extent of cheating in a bacterium
Fitness correlates with the extent of cheating in a bacterium
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DOI：
10.1111/j.1420-9101.2010.01939.x
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发表时间：
2010-04-01
影响因子：
2.1
通讯作者：
Griffin, A. S.
中科院分区：
文献类型：
--
作者：
Jiricny, N.;Diggle, S. P.;Griffin, A. S.
人们越来越意识到微生物群落中合作行为的重要性。对这一观点的经验支持来自于使用被称为“作弊”的突变菌株的实验，这些突变菌株利用了野生型菌株的合作行为。然而，很少有详细的工作来描述合作和作弊菌株的竞争动态。我们通过检查铜绿假单胞菌（Pseudomonas aeruginosa）中清除铁的铁载体分子pyoverdin的产生，在不同程度上测试了关于作弊的适应性后果的三个具体预测。我们创建了一系列产生pyoverdin数量不同的突变体（从配对野生型的1%到96%），并证明这些产生水平与基因活性和结合铁的能力相关。在这些突变体中，我们发现(1)当与合作野生型菌株在混合培养中生长时，突变体的相对适合度与其产生的pyoverdin量呈负相关；(2)野生型菌株在混合培养中的绝对适宜度和相对适宜度与突变体产生的pyoverdin量呈正相关；(3)当在单一栽培中生长时，突变体的绝对适合度与其产生的pyoverdin量呈正相关。总的来说，我们证明了合作的pyoverdin生产是可利用的，并说明了社会行为的变化如何根据社会环境不同地决定适合度。
There is growing awareness of the importance of cooperative behaviours in microbial communities. Empirical support for this insight comes from experiments using mutant strains, termed 'cheats', which exploit the cooperative behaviour of wild-type strains. However, little detailed work has gone into characterising the competitive dynamics of cooperative and cheating strains. We test three specific predictions about the fitness consequences of cheating to different extents by examining the production of the iron-scavenging siderophore molecule, pyoverdin, in the bacterium Pseudomonas aeruginosa. We create a collection of mutants that differ in the amount of pyoverdin that they produce (from 1% to 96% of the production of paired wild types) and demonstrate that these production levels correlate with both gene activity and the ability to bind iron. Across these mutants, we found that (1) when grown in a mixed culture with a cooperative wild-type strain, the relative fitness of a mutant is negatively correlated with the amount of pyoverdin that it produces; (2) the absolute and relative fitness of the wild-type strain in the mixed culture is positively correlated with the amount of pyoverdin that the mutant produces; and (3) when grown in a monoculture, the absolute fitness of the mutant is positively correlated with the amount of pyoverdin that it produces. Overall, we demonstrate that cooperative pyoverdin production is exploitable and illustrate how variation in a social behaviour determines fitness differently, depending on the social environment.