Molecular and cellular bases of adaptation to a changing environment in microorganisms

Abstract

Environmental heterogeneity constitutes an evolutionary challenge for organisms. While evolutionary dynamics under variable conditions has been explored for decades, we still know relatively little about the cellular and molecular mechanisms involved. It is of paramount importance to examine these molecular bases because they may play an important role in shaping the course of evolution. In this review, we examine the diversity of adaptive mechanisms in the face of environmental changes. We exploit the recent literature on microbial systems because those have benefited the most from the recent emergence of genetic engineering and experimental evolution followed by genome sequencing. We identify four emerging trends: (i) an adaptive molecular change in a pathway often results in fitness trade-off in alternative environments but the effects are dependent on a mutation's genetic background; (ii) adaptive changes often modify transcriptional and signalling pathways; (iii) several adaptive changes may occur within the same molecular pathway but be associated with pleiotropy of different signs across environments; (iv) because of their large associated costs, macromolecular changes such as gene amplification and aneuploidy may be a rapid mechanism of adaptation in the short-term only. The course of adaptation in a variable environment, therefore, depends on the complexity of the environment but also on the molecular relationships among the genes involved and between the genes and the phenotypes under selection.

Cooperation in Microbial Populations: Theory and Experimental Model Systems

“…These organisms, which appear simple only at first glance, exhibit tremendous diversity and are able to adapt to a multitude of changing environmental conditions [36,307,382,165]. For example, they balance the cellular demands to optimize growth, uptake and survival under a range of environmental conditions by changing the composition of expressed proteins [382,27,152]. But strategies to adapt do not only involve a controlled change of protein resources.…”

A collection of barcoded natural isolates of Saccharomyces paradoxus to study microbial evolutionary ecology

“…This shows the extent of noise caused by strain transformations and/or biases or noise in barcode quantification (a, b, and c) and the maximum correlation possible between conditions. Correlations between conditions are systematically lower, showing a major effect of growth conditions in relative fitness among strains shown the influence of competition on how specific microbial isolates cope with a novel environment or with a fluctuating environment (Bleuven & Landry, 2016;Lawrence et al, 2012;Osmond & de Mazancourt, 2013;Pekkonen, Ketola, & Laakso, 2013;Van Den Elzen, Kleynhans, & Otto, 2017). In its environment, S. paradoxus is surrounded by an abundant diversity of microbial species and its growth success will depend on the composition of these communities (Kowallik, Miller, & Greig, 2015).…”

“…Fungal microbes are powerful models in genetics and molecular biology and increasingly so in ecological and evolutionary research (Bleuven & Landry, ; Koskella & Vos, ; Landry, Townsend, Hartl, & Cavalieri, ; Marsit et al, ). Among fungi, the genus Saccharomyces , particularly Saccharomyces cerevisiae , is well known for being used as a model system in the laboratory and for being closely associated with other human activities such as beer, wine, and bread making.…”

Interspecific Hybrids Show a Reduced Adaptive Potential Under DNA Damaging Conditions

“…Heterogeneous environments constantly challenge organisms by changing which phenotypes are optimal. Understanding which mechanisms accelerate or slow down adaptation to environmental heterogeneity is a central question in evolutionary biology (Bleuven & Landry 2016) . If changes are rapid and drastic, unless they move to another environment, populations may collapse before adapting.…”