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Social and asocial niche construction in microbial populations.

机译：微生物种群的社会和社会生态位建设。

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摘要

Cooperation presents a major challenge for evolutionary theory: how can competition favor a trait that imposes a cost on the individual expressing it while benefitting another? This challenge has been answered by theory that emphasizes the importance of assortment between individuals that tend to cooperate and those who tend to behave selfishly, or ‘cheat’. Microbial cooperation remains puzzling, given the generally high genetic and taxonomic diversity of most microbial communities. Many microbial populations rely on shared, beneficial extracellular products for an array of functions in nature. However, when these lineages are maintained in liquid cultures, many are invaded and outcompeted by spontaneous ‘cheater’ mutants that forego investments in these products while benefitting from those produced by neighbors. The apparent evolutionary instability of microbial investments in extracellular products in well-mixed laboratory cultures finds a natural parallel in the phenomenon of toxic microalgal blooms. These extremely dense populations of often free-living microalgae destroy populations of competing microalgae and grazing zooplankton that normally control population densities. Bloom populations of planktonic microalgae are unstructured, and seem ill suited for the evolution of cooperation.;In this thesis, I have established a new theoretical framework for understanding the evolution of microbial external goods. This framework highlights the importance of cell-level structure in the distribution of these external products, as well as genetic structuring in populations. This perspective informed an investigation into the social niche of a biofilm-dwelling regulatory mutant of the important biocontrol strain Pseudomonas chlororaphis. In the highly self-structured environment of a bacterial biofilm, a surprising mutualistic association between this mutant and the wild type emerged, underscoring the importance of microbial ecology in understanding the evolution of niche construction. Extending these lessons to the evolutionary problem of exotoxins in free-swimming microalgae yields the novel possibility that fluctuations in density of toxic strains shift a cell-level functioning exotoxin into a true public good that may be exploited by cheaters. I show that exotoxicity can serve cell-level functions in Prymnesium parvum. Despite these cell-level benefits, the existence of nontoxic lineages within toxic blooms hints at a complex interaction between rapid evolutionary and ecological changes in toxic blooms.
机译：合作对进化论提出了一个重大挑战：竞争如何才能支持一种特质，这种特质会给表达它的个人带来成本，同时又会使他人受益呢？理论上已经回答了这一挑战，该理论强调了倾向于合作的个体与倾向于自私或“作弊”行为的个体之间进行分类的重要性。鉴于大多数微生物群落的遗传和分类学多样性普遍很高，微生物合作仍然令人费解。许多微生物种群依赖共享的有益的细胞外产物来实现自然界中的一系列功能。但是，当这些谱系保存在液体培养基中时，许多自发的“骗子”突变体会入侵并胜出，这些突变体会放弃对这些产品的投资，而会从邻居生产的产品中受益。在充分混合的实验室培养物中，微生物对细胞外产物投资的明显演化不稳定性与有毒的微藻开花现象自然相似。这些极度密集的通常自由生活的微藻种群破坏了竞争性微藻种群和通常控制种群密度的放牧浮游动物。浮游微藻的布鲁姆种群是无结构的，似乎不适合于合作的演化。在本文中，我建立了一个新的理论框架来理解微生物外部产品的演化。该框架突出了细胞水平结构在这些外部产物的分布以及人群的遗传结构中的重要性。这种观点指导了对重要生物防治菌株绿假单胞菌生物膜居住调节突变体的社会生态位的调查。在细菌生物膜的高度自我结构化的环境中，该突变体与野生型之间出现了令人惊讶的相互联系，从而强调了微生物生态学在理解生态位构建过程中的重要性。将这些课程扩展到自由游动微藻中外毒素的进化问题中，产生了新的可能性，即毒性菌株密度的波动将细胞水平的功能性外毒素转变为可被作弊者利用的真正的公共物品。我证明了外毒素可以在小白兰中发挥细胞水平的功能。尽管具有这些细胞水平的好处，但在毒性大花中存在无毒谱系提示在毒性大花中快速进化与生态变化之间存在复杂的相互作用。

著录项

  • 作者

    Driscoll, William Wallace.;

  • 作者单位

    The University of Arizona.;

  • 授予单位 The University of Arizona.;
  • 学科 Biology Ecology.;Environmental Sciences.;Biology Evolution and Development.;Biology Microbiology.
  • 学位 Ph.D.
  • 年度 2012
  • 页码 105 p.
  • 总页数 105
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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