Web alert: Adaptive evolution of microbes

Abstract

This review focuses on the adaptive strategies of microbes in the oceans. This study investigated how microbial composition changed spatially and temporally along a climate gradient. This study used two closely related Bacillus strains and observed how positive and negative selective pressures led to gene transfers and adaption. This study used a co-culture of Saccharomyces cerevisiae and Lactobacillus plantarum to show that coevolution prevents the destabilization of community interactions. This study used modelling and empirical experiments to examine the time of adaption as a function of different inoculum sizes in the transfer regime. Findings from this study suggest that changing the order of environmental changes leads to differences in adaptive and genomic changes. This study emphasized setting up conditions specific to a particular microorganism in adaptive evolution experiments. Specifically, they used a semi-continuous bioreactor with a layout that prevented biofilm formation. In natural environments, growth substrates are constantly changing. This study used Escherichia coli and alternated supplying glucose, xylose, glycerol or acetate in the growth medium. This paper describes a model for designing and optimizing adaptive laboratory evolution experiments. This interesting blog post discusses the role of tRNAs in regulating protein expression and hence the ability of microbes to adapt to changing conditions in the environment. This paper posits that microbial communities evolve more rapidly in extreme environments. The extreme environments examined were acid mine drainage, saline lake and hot spring and that was compared to surface ocean, freshwater, and soil. This article focuses on non-microbial systems, but it contains a wonderful description of the first documented laboratory evolution experiment with single-celled organisms, specifically on protist adaption to increasing temperature that was conducted in the 1880's. The take home message of this study is that growth rate and substrate utilization is more influenced by evolutionary history than by climate. Wild type Pseudomonas putida KT2440 cannot grow exclusively on ethylene glycol but that substrate can generate reducing equivalents. Laboratory evolution developed a strain able to grow on ethylene glycol and the study revealed the nature of the mutations required for this new phenotype. While Acidovorax sp. strain JS42 would oxygenate 4-nitrotoluene it would not grow on that substrate. Adaptive evolution experiments generated variants that grew on this new substrate. This review article focuses on using adaptive evolution for strain construction for biotechnological applications.