Analyses of intercellular interaction and genome structure change during heat tolerant evolution by using experimental evolution system with Escherichia coli

利用大肠杆菌实验进化系统分析耐热进化过程中细胞间相互作用和基因组结构变化

基本信息

批准号：
18570219
负责人：
KISHIMOTO Toshihiko
金额：
$ 2.54万
依托单位：
Toho University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

We have researched about the dynamics both of cellular and E. coli population level during adaptation to heat stress (high temperature; above 39 degree). First, we constructed the serially transfer culture system maintaining specific growth rate, then transferred E. coli culture to high temperature (2 degree above past temperature). We could evolve E. coli to accept 45 degree condition that was highest temperature E. coli could survive in minimum conditioned medium. During 39 degree adaptation, just after temperature transition, growth rate decreased rapidly and standard deviation of fluorescence of cellular green fluorescence protein (GFP) of E. coli population enhanced in 2~7days, then growth rate recovered and SD of GFP was decreased for 10-20 days and converged to 39 degree specific values. These results indicated that temperature shift induced diversity of intracellular conditions that might bring the recovery of plasticity of E. coli population, and then adaptation was facilitated by E. coli diversity. At the early stage of 45 degree adaptation, E. coli could grow cell density dependent-manner. This dependency was derived from secreted factors from E. coli, therefore, temperature shift might induce quorum sensing. We have been searching corresponding secreted factors from E. coli culture supernatant. Moreover, average genome DNA content in E. coli cell increased in proportion to adaptation to higher temperature, and interestingly content both of guanine and cytosine decreased according to adaptation to higher temperature. Our results suggested that heat tolerant adaptation and evolution of E. coli might be brought by diversification and/or interaction among E. roll population, and genome DNA content increment and G/C content decrement were observed through fixation process of evolved phenotype.

我们已经研究了适应热应激（高温；高于39度）的细胞和大肠杆菌种群水平的动力学。首先，我们构建了维持特定生长速率的串行转移培养系统，然后将大肠杆菌培养转移到高温（高于过去温度）的高温下。我们可以进化大肠杆菌以接受最高温度大肠杆菌的45度条件，可以在最低条件的培养基中生存。在39度适应期间，在温度转变后，生长速率迅速降低，大肠杆菌群体的细胞绿色荧光蛋白（GFP）的荧光标准偏差在2〜7天增强，然后回收的GFP的生长速率降低10-20天，并融合至39度特定值。这些结果表明，温度转移会引起细胞内条件的多样性，这可能会导致大肠杆菌种群的可塑性恢复，然后通过大肠杆菌多样性促进了适应性。在45度适应的早期阶段，大肠杆菌可以增长细胞密度依赖性曼纳。这种依赖性来自大肠杆菌的分泌因子，因此，温度转移可能会引起法规传感。我们一直在搜索来自大肠杆菌培养上清液的相应分泌因素。此外，大肠杆菌细胞中的平均基因组DNA含量与适应更高温度的成比例增加，有趣的是，鸟嘌呤和胞嘧啶的含量都根据适应更高的温度而降低。我们的结果表明，大肠杆菌的耐热适应和演变可能是通过大肠杆菌种群之间的多样化和/或相互作用引起的，并且通过进化表型的固定过程观察到基因组DNA含量的增量和G/C含量降低。