Institute of Natural and Mathematical Sciences, Massey University at Albany, Private Bag 102 904, North Shore Mail Centre, Auckland, New Zealand.
Evolution. 2013 Nov;67(11):3161-74. doi: 10.1111/evo.12183. Epub 2013 Jul 10.
The idea that bacteria are social is a popular concept with implications for understanding the ecology and evolution of microbes. The view arises predominately from reasoning regarding extracellular products, which, it has been argued, can be considered "public goods." Among the best studied is pyoverdin-a diffusible iron-chelating agent produced by bacteria of the genus Pseudomonas. Here we report the de novo evolution of pyoverdin nonproducing mutants, genetically characterize these types and then test the appropriateness of the sociobiology framework by performing growth and fitness assays in the same environment in which the nonproducing mutants evolved. Our data draw attention to discordance in the fit between social evolution theory and biological reality. We show that pyoverdin-defective genotypes can gain advantage by avoiding the cost of production under conditions where the molecule is not required; in some environments pyoverdin is personalized. By exploring the fitness consequences of nonproducing types under a range of conditions, we show complex genotype-by-environment interactions with outcomes that range from social to asocial. Together these findings give reason to question the generality of the conclusion that pyoverdin is a social trait.
细菌具有社会性的观点是一个流行的概念，对理解微生物的生态学和进化具有重要意义。这种观点主要源于对细胞外产物的推理，有人认为这些产物可以被视为“公共物品”。其中研究最多的是绿脓菌素——一种由假单胞菌属细菌产生的可扩散铁螯合剂。在这里，我们报告了新型绿脓菌素非产生突变体的从头进化，对这些类型进行了遗传特征分析，然后通过在非产生突变体进化的相同环境中进行生长和适应性测定，检验了社会生物学框架的适当性。我们的数据引起了社会进化理论与生物现实之间的不和谐。我们表明，在不需要该分子的条件下，绿脓菌素缺陷基因型可以通过避免生产成本而获得优势；在某些环境中，绿脓菌素是个性化的。通过在一系列条件下探索非产生类型的适应性后果，我们展示了具有社会到非社会等各种结果的复杂基因型-环境相互作用。这些发现共同表明，有理由质疑绿脓菌素是一种社会性特征的结论的普遍性。
