Figure 4. Unicellular K. lactis benefit by associating with multicellular conspecifics.

(a) Unicells (stained red) reversibly adhere to conspecific snowflakes (stained green). (b) Unicells that fail to increase when settling alone m_U=−0.01, 95% CI (−0.14, 0.12)) improve settling performance in mixture with conspecific snowflakes (m_U=0.30, (0.18, 0.43)). However, this benefit disappears when settling with heterospecific snowflakes (S. cerevisiae) (m_U=0.02, (−0.10, 0.15)). The central line is the median, boxes are inter-quartile ranges and whiskers show the range of measured m_U values. (c) Multi-snowflake settling aggregates readily form by indiscriminate attachment among non-relatives during settling. (Pictured are oppositely stained, independently evolved snowflake isolates from Y8 (red) and Y9 (blue) populations.). All scale bars, 25 μm.