Figure 7: Contrasting interactions among multicellular neighbours in K. lactis and S. cerevisiae.
From: Synergistic cooperation promotes multicellular performance and unicellular free-rider persistence
(a) The settling velocity of K. lactis snowflake clusters increases dramatically in high (100%) compared with low (5%) density conditions (Tukey’s HSD: P<0.0001), whereas S. cerevisiae cluster velocity did not significantly differ between density treatments (P=0.305). Central lines show medians, boxes are interquartile ranges and whiskers show the full range of observed settling velocities. (b) Distinct settling behaviours are evident in settling videos, which show solitary S. cerevisiae snowflakes and cohesive groups of K. lactis snowflakes. Images taken from representative high-density settling videos, in which tracks show snowflake position across 20 frames (=1 s) and track colours reflect relative cluster velocity. It is noteworthy that only 5% of clusters are stained, so visible clusters need not appear to touch to be physically associated. (c) Contrasting interactions among neighbouring snowflakes differentiate competitive and cooperative settling. Focal snowflake cluster size is the primary determinant of settling velocity in multicellular S. cerevisiae, whereas neighbouring snowflakes overwhelmingly contribute to rapid settling in K. lactis. Neighbouring clusters actually reduce settling velocity in S. cerevisiae, consistent with local competition among snowflakes via hindered settling. Error bars denote the 95% CI.
