RAYMOND E. GOLDSTEIN - Phototaxis and the Evolution of Multicellularity

Raymond E. GOLDSTEIN

Wednesday, May 15, 2024
1:30 p.m. — ConfIV (E244)

Phototaxis and the Evolution of Multicellularity

A fundamental issue in biology is the nature of evolutionary transitions from unicellular to multicellular organisms. Green algae are models for this transition, as they span from the unicellular species to multicellular ones with tens of thousand of cells, all of which swim through the action of flagella that are closely related to the cilia found throughout the human body. The mechanism by which these organisms steer toward light (phototaxis) is of particular interest since they lack a nervous system and intercellular connections; steering is a consequence of the response of individual  cells to light. In this talk I will describe experimental and theoretical work on the physical mechanism of phototaxis in species of green algae, spanning 3 orders of magnitude in cell number. We find an evolutionarily conserved dynamics, with a tuning between the time scales for an adaptive flagellar response to changing light levels and the spinning frequencies of the microorganisms. The implication of these results for the evolution of multicellularity are discussed.