(L-R) John Koschwanez and Andrew Murray
Many unicellular organisms secrete enzymes that release nutrients from their environment. But most of the nutrients can’t be captured by the cell’s nutrient transporters and instead diffuse away from the cell. This presents a problem for a cell growing in an environment where the nutrients are scarce and must be broken down before being imported.
Multicellularity could solve this problem because each cell in a multicellular clump of cells could capture some of the nutrients released by its neighbor. We tested this hypothesis using the budding yeast Saccharomyces cerevisiae. Yeast can’t grow from a single cell in low concentrations of sucrose because the sucrose must be broken down by the cell wall enzyme invertase before the resulting monosaccharides, glucose and fructose, can be imported. But if the cell is part of a multicellular clump, the cell can capture the monosaccharides released by the neighboring cells. Many isolates of yeast from the wild are multicellular, and we inserted a wild allele into our lab yeast to make it multicellular. We found that a clump of cells could grow in a low-sucrose environment where single cells could not. We speculate that the benefit of sharing public goods, such as nutrients, within a clump of cells was the original selection for multicellularity.
Read more in PLoS Biology [August 9th, 2011]
Read More in the Harvard Gazette [August 9th, 2011]