PDF(Pubmed)
Abstract：
Intrinsic rates of genetic mutation have diverged greatly across taxa and exhibit statistical associations with several other parameters and features. These include effective population size (Ne), genome size, and gametic multicellularity, with the latter being associated with both increased mutation rates and decreased effective population sizes. However, data sufficient to test for possible relationships between microbial multicellularity and mutation rate (µ) are lacking. Here, we report estimates of two key population-genetic parameters, Ne and µ, for Myxococcus xanthus, a bacterial model organism for the study of aggregative multicellular development, predation, and social swarming. To estimate µ, we conducted an ∼400-day mutation accumulation experiment with 46 lineages subjected to regular single colony bottlenecks prior to clonal regrowth. Upon conclusion, we sequenced one clonal-isolate genome per lineage. Given collective evolution for 85,323 generations across all lines, we calculate a per base-pair mutation rate of ∼5.5 × 10-10 per site per generation, one of the highest mutation rates among free-living eubacteria. Given our estimate of µ, we derived Ne at ∼107 from neutral diversity at four-fold degenerate sites across two dozen M. xanthus natural isolates. This estimate is below average for eubacteria and strengthens an already clear negative correlation between µ and Ne in prokaryotes. The higher and lower than average mutation rate and Ne for M. xanthus, respectively, amplify the question of whether any features of its multicellular life cycle-such as group-size reduction during fruiting-body development-or its highly structured spatial distribution have significantly influenced how these parameters have evolved.
摘要：
遗传突变的内在速率在分类单元之间差异很大，并与其他几个参数和特征表现出统计关联。这些包括有效人口规模(Ne)，基因组大小，和配子多细胞性，后者与突变率增加和有效种群规模减少有关。然而,缺乏足以测试微生物多细胞性与突变率（µ）之间可能关系的数据。这里,我们报告了两个关键群体遗传参数的估计，Ne和µ，黄药粘球菌,用于研究聚集性多细胞发育的细菌模型生物，捕食,社会蜂拥而至。要估计µ，我们对46个谱系进行了400天的突变积累实验，这些谱系在克隆再生长之前经历了常规的单菌落瓶颈。一结束,我们对每个谱系的一个克隆分离物基因组进行了测序。考虑到所有线路的85,323代的集体进化，我们计算出每代每个位点的每个碱基对突变率为~5.5×10-10，是自由生活的真细菌中突变率最高的细菌之一。鉴于我们对µ的估计，WederivedNeat～107fromneutraldiversityat～该估计值低于真细菌的平均值，并加强了原核生物中µ和Ne之间已经明显的负相关。黄药的突变率和Ne高于和低于平均，分别,放大了以下问题：其多细胞生命周期的任何特征，例如子实体发育过程中的群体大小减少，或其高度结构化的空间分布是否显着影响了这些参数的演变方式。
