Adaptation of Escherichia coli to long-term batch culture in various rich media

Publication date: April 2018Source: Research in Microbiology, Volume 169, Issue 3Author(s): Lacey L. Westphal, Jasmine Lau, Zuly Negro, Ivan J. Moreno, Wazim Ismail Mohammed, Heewook Lee, Haixu Tang, Steven E. Finkel, Karin E. KramAbstractExperimental evolution studies have characterized the genetic strategies microbes utilize to adapt to their environments, mainly focusing on how microbes adapt to constant and/or defined environments. Using a system that incubates Escherichia coli in different complex media in long-term batch culture, we have focused on how heterogeneity and environment affects adaptive landscapes. In this system, there is no passaging of cells, and therefore genetic diversity is lost only through negative selection, without the experimentally-imposed bottlenecking common in other platforms. In contrast with other experimental evolution systems, because of cycling of nutrients and waste products, this is a heterogeneous environment, where selective pressures change over time, similar to natural environments. We determined that incubation in each environment leads to different adaptations by observing the growth advantage in stationary phase (GASP) phenotype. Re-sequencing whole genomes of populations identified both mutant alleles in a conserved set of genes and differences in evolutionary trajectories between environments. Reconstructing identified mutations in the parental strain background confirmed the adaptive advantage of some alleles, but also identif...

Source: Research in Microbiology - July 10, 2018 Category: Microbiology Source Type: research