Disadvantages and benefits of evolved unicellularity versus multicellularity in budding yeast

Abstract

Multicellular organisms appeared on Earth through several independent major evolutionary transitions. Are such transitions reversible? Addressing this fundamental question entails understanding the benefits and costs of multicellularity versus unicellularity. For example, some wild yeast strains form multicellular clumps, which might be beneficial in stressful conditions, but this has been untested. Here, we show that unicellular yeast evolve from clump‐forming ancestors by propagating samples from suspension after larger clumps have settled. Unicellular yeast strains differed from their clumping ancestors mainly by mutations in the AMN1 (Antagonist of Mitotic exit Network) gene. Ancestral yeast clumps were more resistant to freeze/thaw, hydrogen peroxide, and ethanol stressors than their unicellular counterparts, but they grew slower without stress. These findings suggest disadvantages and benefits to multicellularity and unicellularity that may have impacted the emergence of multicellular life forms.

Evolution of multicellularity and unicellularity in yeastS. cerevisiaeto study reversibility of evolutionary trajectories

“…Previous studies have reported that wild type yeast cluster strains were resistant to free/thaw treatment (Kuzdzal-Fick et al, 2019) and the stress resistance was measured using a cell counter. In contrast, in the present study, we used spot assay to investigate the sensitivity of yeast cluster phenotype to cold (20°C) and heat stress (37°C).…”

“…Several past studies have examined the evolution of multicellular snowflake clusters from unicellular yeast S. cerevisiae (Ratcliff et al, 2012, Ratcliff et al, 2013, Koschwanez et al, 2011a, Rebolleda-Gomez et al, 2012, Driscoll & Travisano, 2017, Jacobeen et al, 2018, Rebolleda-Gomez & Travisano, 2018, Kuzdzal-Fick et al, 2019, Herron et al, 2019. The studies have demonstrated that, under selection, the transition from unicellular to multicellularity is relatively quick (of the order of a few dozen generations).…”

Metabolic Heat in Microbial Conflict and Cooperation

“…Cells may also aggregate by surface attachment and by active movement toward groups. Many possible costs and benefits of cellular aggregation occur [18][19][20][21][22] . However, heat in microbial aggregates has not been widely discussed.…”

Metabolic Heat in Microbial Conflict and Cooperation

“…Cells may also aggregate by surface attachment and by active movement toward groups. Many possible costs and benefits of cellular aggregation occur [19][20][21][22][23] . However, heat in microbial aggregates has not been widely discussed.…”