Investigating Sexual Recombination for Applications in Adaptive Laboratory Evolution

The generation of biofuels and other industrially desirable chemicals can be achieved through the use of biocatalysts. Biocatalysts offer a versatile and environmentally friendly alternative to chemical synthesis. However, industrial production of bio-based compounds faces challenges such as low levels of product yield and titer, and the frequent toxicity of industrially desirable conditions. Biocatalyst robustness in the presence of harsh conditions can be improved by developing tolerant phenotypes. Unfortunately, tolerant phenotype development is often too complex for rational engineering. Adaptive Laboratory Evolution (ALE), serves as a powerful alternative method. ALE has demonstrated substantial success in producing strains that are highly tolerant to various industrially relevant inhibitory conditions and is not limited by knowledge of rational targets for strain design. ALE relies upon mutation and selection to evolve a population toward local or global optima along the organism-of-interest’s fitness landscape in the chosen environment. Mutations represent dimensions in the fitness landscape where various mutational combinations lead to changes in fitness. Previous work has attempted to enhance the fitness landscape explored in ALE by introducing sexual recombination to asexual evolving strains, producing a more combinatorial approach. We present experimental evidence of some of the theorized advantages of sexual recombination, including the ability of sexual recombination to reduce genetic load. We then delve into the effectiveness of sexual recombination to better quantify the advantage of a sexual strain and to carry over the results toward strain development and gain a better understanding of the evolutionary process in microbial systems.