生物多样性 ›› 2016, Vol. 24 ›› Issue (9): 1056-1061.DOI: 10.17520/biods.2016143

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不同进化类型大肠杆菌的适合度频率依赖性

倪川, 朱璧如, 张大勇*()   

  1. 北京师范大学生物多样性与生态工程教育部重点实验室, 北京 100875
  • 出版日期:2016-09-20 发布日期:2016-10-09
  • 通讯作者: 张大勇
  • 基金资助:
    国家自然科学基金(31030014)

Frequency dependent fitness in different evolved Escherichia coli lines

Chuan Ni, Biru Zhu, Dayong Zhang*()   

  1. Key Laboratory for Biodiversity Science and Ecological Engineering of Ministry of Education, Beijing Normal University, Beijing 100875
  • Online:2016-09-20 Published:2016-10-09
  • Contact: Zhang Dayong

摘要:

进化实验中使用竞争实验测量两个物种或基因型的相对适合度时, 通常假定两者的适合度差异是恒定的。然而竞争双方的相互作用可能导致适合度差异受到初始相对频率的影响。本研究通过测量两种进化株系的大肠杆菌(Escherichia coli)在不同初始相对频率下的相对适合度, 分析了初始相对频率对相对适合度的影响。结果发现高氮进化株系相对低氮进化株系的相对适合度随其初始相对频率的减小而增加, 表现出显著的负频率依赖。两种株系在培养高氮株系的滤出液中均没有显著的生长, 在培养低氮株系的滤出液中均有生长, 但高氮株系的细胞加倍次数是低氮株系的3倍, 说明导致适合度出现负频率依赖的原因可能是低氮株系的竞争能力较低, 不能完全利用培养基中的资源; 也可能是低氮株系的代谢产物能被高氮株系利用, 产生互养作用。不同的相互作用可能导致不同的初始相对频率与相对适合度间的关系, 因此, 为了更准确地衡量适合度, 进化实验中需要考虑初始相对频率对相对适合度的影响。

关键词: 竞争实验, 初始相对频率, 互养作用, 他感作用

Abstract:

Differences in fitness between two species or genotypes is usually assumed to be constant when competition experiments are used to measure relative fitness in evolutionary experiments. However, interactions between competitors may lead to frequency-dependence in fitness. We measured the relative fitness of two types of evolved lines of Escherichia coli under different initial relative frequencies to analyze the effects of initial relative frequency on relative fitness. Competed with the low nitrogen evolved lines, the high nitrogen evolved lines displayed increased relative fitness with decreased initial relative frequency, which suggests negative frequency dependence. Both types did not grow in the filtrate from high nitrogen evolved lines, but grew in the filtrate from low nitrogen evolved lines. However, the number of cell doublings of the high nitrogen evolved lines was three times higher than that of the low nitrogen evolved lines. One probable explanation for the negative frequency dependent fitness was that the low nitrogen evolved lines had weaker resource competitive ability and could not sufficiently use resources. Another explanation was that the high nitrogen evolved lines could use some metabolites produced by the low nitrogen evolved lines, which suggests the existence of cross-feeding interaction. Different interactions may lead to different relationships between relative fitness and initial relative frequency. Therefore, we need to account for the effects of initial relative frequency on relative fitness to more accurately measure fitness in evolutionary experiments.

Key words: competition experiment, initial relative frequency, cross-feeding interaction, allelopathic interaction