Evolutionary potential, cross‐stress behavior and the genetic basis of acquired stress resistance in Escherichia coli

Molecular Systems Biology

Martin Dragosits¹  Vadim Mozhayskiy¹  Semarhy Quinones-Soto¹  Jiyeon Park¹ 

[1] UC Davis Genome Center, University of California-Davis, Davis, CA, USA

关键词: cross‐stress protection;    evolutionary trade‐offs;    microbial evolution;    stress adaptation;   

DOI  :  10.1038/msb.2012.76

来源: Wiley

【 摘 要 】

Abstract

Bacterial populations have a remarkable capacity to cope with extreme environmental fluctuations in their natural environments. In certain cases, adaptation to one stressful environment provides a fitness advantage when cells are exposed to a second stressor, a phenomenon that has been coined as cross-stress protection. A tantalizing question in bacterial physiology is how the cross-stress behavior emerges during evolutionary adaptation and what the genetic basis of acquired stress resistance is. To address these questions, we evolved Escherichia coli cells over 500 generations in five environments that include four abiotic stressors. Through growth profiling and competition assays, we identified several cases of positive and negative cross-stress behavior that span all strain–stress combinations. Resequencing the genomes of the evolved strains resulted in the identification of several mutations and gene amplifications, whose fitness effect was further assessed by mutation reversal and competition assays. Transcriptional profiling of all strains under a specific stress, NaCl-induced osmotic stress, and integration with resequencing data further elucidated the regulatory responses and genes that are involved in this phenomenon. Our results suggest that cross-stress dependencies are ubiquitous, highly interconnected, and can emerge within short timeframes. The high adaptive potential that we observed argues that bacterial populations occupy a genotypic space that enables a high phenotypic plasticity during adaptation in fluctuating environments.

Synopsis

Escherichia coli cells were evolved over 500 generations and profiled in four abiotic stressors to observe several cases of emerging cross-stress behavior whereby adaptation to one stressful environment provided fitness advantage when exposed to a second stressor.

• Cross-stress dependencies were found to be ubiquitous, highly interconnected and can emerge within short timeframes.
• Several targets were implicated in adaptation and cross-stress protection, including genes related to iron transport and flagella.
• Adaptation in a first stress can lead to higher fitness to a second stress when compared with cells adapted only in the latter environment.
• Adaptation to any specific stress and the growth media was found to be generally independent.

【 授权许可】

CC BY-NC-SA   
Copyright © 2013 EMBO and Macmillan Publishers Limited

Creative Commons Attribution License, which permits distribution, and reproduction in any medium, provided the original author and source are credited. This license does not permit commercial exploitation without specific permission.