School of Molecular Bioscience, University of Sydney, New South Wales, Australia.
Microbiol Mol Biol Rev. 2012 Sep;76(3):597-625. doi: 10.1128/MMBR.05028-11.
Diversity in adaptive responses is common within species and populations, especially when the heterogeneity of the frequently large populations found in environments is considered. By focusing on events in a single clonal population undergoing a single transition, we discuss how environmental cues and changes in growth rate initiate a multiplicity of adaptive pathways. Adaptation is a comprehensive process, and stochastic, regulatory, epigenetic, and mutational changes can contribute to fitness and overlap in timing and frequency. We identify culture history as a major determinant of both regulatory adaptations and microevolutionary change. Population history before a transition determines heterogeneities due to errors in translation, stochastic differences in regulation, the presence of aged, damaged, cheating, or dormant cells, and variations in intracellular metabolite or regulator concentrations. It matters whether bacteria come from dense, slow-growing, stressed, or structured states. Genotypic adaptations are history dependent due to variations in mutation supply, contingency gene changes, phase variation, lateral gene transfer, and genome amplifications. Phenotypic adaptations underpin genotypic changes in situations such as stress-induced mutagenesis or prophage induction or in biofilms to give a continuum of adaptive possibilities. Evolutionary selection additionally provides diverse adaptive outcomes in a single transition and generally does not result in single fitter types. The totality of heterogeneities in an adapting population increases the chance that at least some individuals meet immediate or future challenges. However, heterogeneity complicates the adaptomics of single transitions, and we propose that subpopulations will need to be integrated into future population biology and systems biology predictions of bacterial behavior.
适应反应的多样性在物种和种群中很常见，尤其是当考虑到在环境中经常发现的大种群的异质性时。通过关注单一克隆群体在经历单一转变时发生的事件，我们讨论了环境线索和生长速率的变化如何引发多种适应性途径。适应是一个综合的过程，随机、调节、表观遗传和突变变化可以有助于适应和适应的时间和频率重叠。我们将培养历史确定为调节适应和微观进化变化的主要决定因素。转变前的种群历史决定了由于翻译错误、调节随机差异、老化、受损、欺骗或休眠细胞的存在以及细胞内代谢物或调节剂浓度的变化而导致的异质性。细菌来自密集、生长缓慢、压力大还是结构化的状态很重要。由于突变供应、应急基因变化、相位变化、水平基因转移和基因组扩增的变化，基因型适应取决于历史。表型适应为应激诱导突变或噬菌体诱导或生物膜中的基因型变化提供了基础，从而提供了连续的适应可能性。进化选择在单一转变中还提供了多种适应性结果，通常不会导致单一的更适应类型。适应种群中的异质性总量增加了至少一些个体能够应对当前或未来挑战的机会。然而，异质性使单一转变的适应组学复杂化，我们提出需要将亚群整合到未来的细菌行为的种群生物学和系统生物学预测中。
